Dyeing of Sisal and other Plant Fibres: A Handbook for Craft Instructors (NRI) Part 2: Use of Different classes of dyes Reactive dyes Direct dyes Acid dyes Basic dyes Disperse dyes

Dyeing of Sisal and other Plant Fibres: A Handbook for Craft Instructors (NRI)

Part 2: Use of Different classes of dyes

Reactive dyes

Introduction

The direct, acid, basic and disperse dyes are attached to the fibre by purely physical bonds. The reactive dyes were developed in order to give better fastness properties by chemically fixing the dye to the fibre. They are often derived by linking simple acid dyes to a chemical which combines with the cellulose in the fibre. Reactive dyes of special interest to the craft worker are those that can be applied in the cold using simple equipment (one method has been described fully by Canning et al., 1 977).

Manufacturers' trade names

Reactive dyes are of several types, ranging from those that can be applied in the cold, such as the 'Procion MX' range from Imperial Chemical Industries plc (ICI), to those that are usually applied at higher temperatures, such as the 'Procion H' range. Only the 'Procion MX' and 'Dylon Cold' dyes have been investigated at TDRI.

Some other ranges which contain similar dyes are*:

'Acticrom F' (Mult)	'Mikacion M' (KYK)
'Amaryl' (Amar)	Ostazin' (Chem)
'Basilen M' (BASF)	'Vilmafix A' (VIL)
'Chemictive' (CE)	'Xiron' (FW)
'Helaktyn F' (POL)

Dyes in some ranges are slightly less reactive than the 'Procion MX' dyes but could probably be applied to sisal by methods similar to that described in this section; some examples are*:

'Cibacron' (CGY)
'Drimarene K' (S)
'Levafix E' and 'EA' (BAY)
'Temazol' (HOE)

Choice of dyes

Tests carried out at TDRI (Canning and Jarman, 1974; Edwards and Canning, 1981) for light fastness, water fastness and penetration have shown that of the twenty-five 'Procion MX' dyes available in April 1982, the following nine are the best choices for dyeing sisal and similar fibres:

Procion Yellow MX-8G (Cl Reactive Yellow 86) Procion Yellow MX-4R (Cl Reactive Orange 14)

Procion Orange MX-G	(Cl Reactive Orange 1)
Procion Red MX-G	(Cl Reactive Red 5)
Procion Red MX-5B	(Cl Reactive Red 2)
Procion Red MX-8B	(Cl Reactive Red 11)
Procion Rubine MX-B	(Cl Reactive Red 6)
Procion Blue MX-3G	(Cl Reactive Blue 1)
Procion Brown MX-3RD	(not listed in the Colour Index)

A further dye found satisfactory, Procion Yellow MX-4G, has been withdrawn. Equivalents (Cl Reactive Yellow 22) are available from other manufacturers (i.e. BASF, CE, KYK, Mult and VIL, see Appendices 2 and 3).

The following dyes penetrate less well into the fibre but can be used when durability is not of prime importance:

Procion Yellow MX-3R	(Cl Reactive Orange 86)
Procion Yellow MX-GR	(Cl Reactive Yellow 7)
Procion Orange MX-2R	(Cl Reactive Orange 4)
Procion Scarlet MX-G	(Cl Reactive Red 8)
Procion Scarlet MX-3G	(not listed in the Colour Index)
Procion Blue MX-R	(Cl Reactive Blue 4)
Procion Blue MX-2G	(Cl Reactive Blue 109)
Procion Blue MX-4GD	(Cl Reactive Blue 168)
Procion Blue MX-7RX	(Cl Reactive Blue 161)
Procion Navy MX-4RD	(not listed in the Colour Index)

From the nine 'Procion MX' dyes recommended for sisal-like fibres a wide range of shades can be obtained which should meet the needs of any craft worker. In fact over one hundred shades including yellows, oranges, reds, violets, blues, greens, browns and a black have been produced at TDRI using only three of these dyes- Procion Yellow MX-8G, Procion Red MX-5B and Procion Blue MX-3G (see Table 1).

With 'Dylon Cold' dyes, shades A.10 Primrose, A.16 Camellia, and A.28 Riviera Blue are satisfactory for mixing to produce a wide range of shades. Of the remaining 'Dylon Cold' dyes, most will produce satisfactory colours but the following do not penetrate into the fibre and should be avoided:

Dylon Cold A.13 French navy
Dylon Cold A.15 Tartan green
Dylon Cold A.17 Cafe au fait
Dylon Cold A.50 Charcoal

Application of dyes

The use of dyes which are chemically reactive toward fibres is a new concept in dyeing. However, when exhaust dyeing using dyes such as ICI 'Procion MX' or Dylon 'Cold', the method of application differs from traditional methods only in that dyeing takes place in the cold.

In exhaust dyeing (see Glossary) the fibre is immersed in a dye solution to which salt is added. When the dye has been adsorbed by the fibre, alkali (usually soda ash) is added to the dyebath and the fibre is left in this solution for a further period of time. The alkali causes most of the adsorbed dye to react with the fibre and fix in such a way that it is impossible to remove the colour with water, giving extremely high water fastness. However, the loose dye must be either removed by hot water washing, or fixed to the fibre by after-treatment. If this is not done, the water fastness will be poor. For some end-uses a combination of washing and after-treatment may be required.

The amounts of salt and soda to be used in exhaust dyeing vary with the depth of shade. Those generally recommended by ICI for cotton dyeing with 'Procion MX' dyes are given in Table 2.

Table 2: Recommended concentrations of common salt and soda ash to be used with ICI 'Procion MX' dyes

Although these quantities will produce satisfactory results with sisal, experienced dyers may vary the composition of the dyebath since salt and soda requirements are also influenced by:

(i) the relative costs of the salt, soda and dyestuff; and

(ii) the exhaustion characteristics of the dye.

By varying the dyebath composition, it is possible to determine the optimum conditions for producing specific colours at the lowest cost .

Penetration of dye into the fibre is improved considerably by the use of a warm process and this is recommended for articles such as carpets, which will be subjected to abrasive wear. However, temperatures above 50°C should not be used since too much of the dye will lose its reactivity through reaction with water.

An alternative method of applying these dyes, pad-batch dyeing, has been described by Canning et al. (1977) and will be mentioned only briefly. However, workers who use this method will find the information given in this handbook on after-treatments and blending useful. In the pad-batch method the fibre is first wetted with a concentrated alkaline dye solution ('padding') and then left in a wet state for a period of time ('batching') to allow the dye to penetrate and fix to the fibre strands. The method makes very effective use of the dye although, as with exhaust dyeing, washing is needed to remove unfixed dye.

The exhaust method is easier to control, therefore it should be used when producing matched shades. However, the pad-batch method (although it can be a little messy) will usually be less costly and less time consuming. Since it allows dyes to penetrate uniformly into the structure of yarns and fabric, the pad-batch method is ideally suited to the dyeing of these materials.

Most craft workers will not be familiar with reactive dyes. However, provided that the following points are borne in mind, they should experience little difficulty.

1. The reactive dyes react not only with fibres, but also with water and body tissues. Therefore the dyes need careful handling. Avoid breathing dye powder by wearing a mask, wear gloves when handling and quickly wash off any dye which gets on the skin (see Safety precautions and first aid treatment).

2. The reactivity, which is essential for the production of water fast shades, is destroyed when moisture is present. The loss of reactivity is considerably more rapid when the dye is also warm or alkaline (after adding soda). Make sure therefore that:

(i) Dye powders are stored in airtight containers in a cool place.

(ii) Dye solutions are kept cool-especially if alkali (soda) has been added.

(iii) Dye solutions are used immediately after being prepared-they must not be stored for later use.

3. Despite taking all precautions, some deterioration will occur and not all of the dye will fix to the fibre. Unless the deteriorated dye is removed by hot water washing or fixed to the fibre by after-treatment, the potentially excellent water fastness properties of these colours will not be achieved. The choice of method must be made before dyeing is started and the following points should be taken into consideration:

(i) Use of hot water washing to remove loose dye: Hot washing has the advantage that any potential health hazard from loose dye is avoided without the use of additional chemicals which could themselves be potentially harmful. Fibre finished in this way is more likely to find acceptance for articles such as children's toys. However, with some dyes-especially reds and in deep colours-several hot washes may be needed to remove all the loose dye.

(ii) Use of cationic after-treatment to chemically fix the loose dye: Some commercial after-treating agents are very effective in fixing loose dye and it has been found possible to eliminate the hot wash normally needed to obtain good colour fastness. By using these treatments, dye could be saved since the colours obtained will be deeper than those obtained after washing the fibre. Although these treatments are widely used, workers should check with their marketing organisation that the dyed fibre will be suitable for its intended end-use.

Recipe for producing an Emerald Green Shade on 2.5 Kg of Sisal

This recipe is based on the use of the exhaust dyeing method-reactive dyes cannot be applied by the standing bath method .

Materials and equipment required

Sisal		2.5 kg
Procion Yellow MX-8G	37.5 g	(1.5 per cent on fibre)
Procion Blue MX-3G	37.5 g	(1.5 per cent on fibre)
Common salt (sodium chloride)	2.25 kg	(45 g/l)
Soda ash	400 g	(8 9/l)
Spring balance
Laboratory balance
Beakers (or similar containers)	4
Buckets
Dye vat		(minimum capacity 60 litres)
Measuring cylinder or dipstick
Stirring rods		1 small for bucket; 1 long for dye vat
Water		50 litres (Liquor ratio 20:1)
Drying lines

Preparing for dyeing

Preparing for dyeing (continued)

Preparing for dyeing (continued)

Dyeing

Dyeing (continued)

Dyeing (continued)

Dyeing (continued)

Removal of unfixed dye by washing

Figure Removal of unfixed dye by washing (continued)

After-treatment

Safety note: After-treating agents are acidic and in concentrated form can be corrosive causing skin burns. The concentrates should therefore be handled with care. Users should wear protective clothing and have ready access to a copious supply of water. Once diluted, the agents are less dangerous but similar precautions should be taken (see Safety precautions and first aid treatment).

Introduction

Unfixed dye is usually removed from the fibre by boiling in detergent and washing in hot and cold water as described in the recipe. However, since this treatment requires a metal (preferably stainless steel) vessel and a source of heat it can be expensive for the craft worker. However, a new method has been developed at TDRI which is both simpler and cheaper. The unfixed dye is treated with a cationic agent which forms an ionic bond with the water solubilising group on the dye molecule. The larger molecule which is formed becomes trapped in the internal structure of the fibre making the dye more water fast. After-treatment causes some loss of light fastness and some change in colour. The agents mentioned here do not produce marked changes in colour.

Fixing Agent IS (Textile Dyestuffs and Chemicals Ltd) can be used to give a low cost treatment with no appreciable loss of light fastness. Alternative agents* are:

Hydrocol KNC (Rudolf and Co. KG)
Sandofix WE-56 (S)
Fixitol P (Durham Chemicals Distributors Ltd)
Matexil FC-PN (ICI)

Of these, the Hydrocol and Fixitol cause the least loss of light fastness but the effectiveness of Fixitol tends to vary with different dyes. Both Matexil and Sandofix cause appreciable loss of light fastness of some shades.

The amount of an agent required depends on the amount of loose dye in the fibres- deeper colours need larger amounts of agent than pale shades, and pad-batch dyed fibre will need more agent than exhaust dyed fibre. Also, fibre that has been hot washed will need less agent than unwashed fibre. Craft workers will need to experiment to find the optimum level of treatment for their fibre. The following methods for use with Fixing Agent IS will provide a basis for experiments.

There are two alternative methods for applying the agents-an exhaust method, and a pad-batch method. The pad-batch method gives better results but the fibre must first be dried.

In the following methods it is assumed that the fibre has been dyed by the pad-batch method using 20 9 of dyestuff in each litre of dye liquor (2 per cent on weight of fibre) then washed by rinsing in cold water only. The method is also based on the use of Fixing Agent IS in dry powder form.

The manufacturers of Fixing Agent IS recommend that the agent be used at 50 - 60°C in soft water slightly acidified with acetic acid. However, satisfactory results have been obtained at TDRI using the agent in the cold without acid. It is recommended though that alkaline waters, such as those softened with soda, are rendered just acidic with acetic acid before use. Anionic substances must be avoided so fibre must be rinsed free from wetting agents such as soaps or washing-up liquid.

Pad-batch method

1. Take 1 litre of water for each kilogram of fibre of the same colour to be treated. Pour this into a bucket or other suitable vessel.

2. Read section on Safety and first aid treatment. Weigh out an amount of Fixing Agent IS powder equivalent to 45 9 for each litre of water taken (in experiments at TDRI the amount of Fixing Agent IS was halved and the water fastnesses of the resultant colours were still of a high order).

3. Mix the after-treating agent to a smooth paste with a little water from the bucket.

4. Rinse the pasted powder into the bucket of water and stir well until all the powder has dissolved.

5. Divide the dyed, rinsed and dried fibre into small bundles.

6. Take one bundle of the fibre and dip it briefly into the after-treatment liquor (about 5 seconds, but no longer). Knead and swill the fibre round whilst it is immersed to ensure that every strand is wetted.

7. Immediately squeeze the excess liquor on the fibre back into the bucket. The fibre should take up its own weight of liquor but not be so wet that it drips. Each litre of liquor will treat 1 kg of fibre.

8. Place the wet fibre into a plastic bag to prevent it from drying.

9. Repeat steps 6, 7 and 8 using the same plastic bag. Surplus liquor can be saved for later use but do not use it for a new colour unless it is clean.

10. When all the fibre of one colour has been wetted with after-treatment liquor, close the bag and leave it overnight in order that the after-treating agent can penetrate into the fibre to fix loose dye.

11. Remove the fibre from the bag and rinse surplus after-treating agent and any loose colour from the surface of the fibre with cold clean water.

12. Hang the fibre in a shady place to dry.

Exhaust method

Note: This method may be used on either wet or dry fibre. However, since better results are obtained when using wet fibre, it is best used directly after the first rinse following the dyeing stage.

1. Take 5 litres of water for each kilogram (dry weight) of fibre to be treated. Pour this into the bucket or other suitable vessel (with dry fibre use 6 litres for each kilogram of fibre). The fibre must be all of the same colour.

2. Read section on Safety precautions and first aid treatment. Weigh out an amount of Fixing Agent IS powder equivalent to 45 9 for each kilogram of fibre to be treated (4.5 per cent on weight of fibre).

3. Mix the after-treating agent to a smooth paste with a little of the water from the bucket.

4. Rinse the pasted powder into the bucket of water and stir well until the powder has dissolved.

5. Place the dyed and rinsed fibre into the liquor ensuring the whole amount is immersed rapidly.

6. Stir well for at least 5 minutes-repeated dipping of the fibre, ensuring it is immersed each time, gives effective stirring.

7. Leave the fibre in the liquor for a further 5 hours stirring frequently within the first hour then at intervals of about 30 minutes.

8. Remove the fibre and rinse it in clean water to remove any loose dye and aftertreating agent.

9. Hang the fibre in the shade to dry.

10. Discard the liquor where it will not contaminate food or water.

Storage

The agents are reported to remain stable for 6 - 12 months when stored in cool places (20 - 30°C). However, the agents mentioned in this handbook remained effective after being kept in the laboratory at TDRI for 2 years but this is no guarantee that they will remain effective for so long in the tropics.

Direct dyes

Introduction

The direct dyes were introduced primarily for use on cotton. Unlike the reactive dyes (see pp. 41 - 55) they do not react chemically with fibres but are retained by physical forces. Dyes of this type are said to be 'substantive', but are sometimes referred to es 'cotton' dyes.

Manufacturers' trade names

Most dyestuff manufacturers offer one or more ranges of direct dyes for cotton, for example:

'Airedale' end 'Benzanil' (YCL)
'Chloramine'(S)
'Chlorazol' end 'Durazol' (ICI)
'Benzo', 'Sirius' end 'Sirius Supra' (BAY)

Instructions given in this section for using direct dyes may be used with all direct dyes regardless of the source. Some manufacturers, however, offer dyes intended for application by special techniques. Bayer's range of 'Benzo Cuprol' dyes, for example, are applied initially in the same way as other direct dyes but develop their characteristically high light and water fastness properties and their final colour only when the dyed shades have been after-treated with copper sulphate . If dyes of this type are used, the manufacturers' special instructions must be followed carefully.

Figure Table 3 - Method of application for direct dyes of different classes to produce level colours

Classification of direct dyes

Some of the direct dyes (Class A) will produce level colours using the normal method of application, others (Class B) will give level colours with controlled addition of salt, whilst the rest (Class C) require very careful heating and application of salt to produce level colours. Unfortunately, dye manufacturers usually do not indicate the class of a particular dyestuff. The instructions given on pp. 58 - 60 are therefore suitable for a Class C dye but dyers will discover by trial and error to which class a dye may belong. They can then use Table 3 as a guide to the appropriate method of application.

Choice of dyes

With the large number of direct dyes that are available it is not possible to list all those suitable for the craft dyeing of sisal. However, most ranges of direct dyestuffs include dyes that will either penetrate fairly deeply into sisal fibres, or that can be used to produce light or water fast colours.

A number of ICI direct dyes have been examined at TDRI and it was found that generally the Class A dyes penetrated most deeply into sisal. Unfortunately, this group of dyes generally produces colours with lower water fastness than other types of direct dyes and the colours produced will usually need after-treatment with a cationic after-treating agent. Some examples of Class A direct dyes with fairly good light-fastness properties are:

Durazol Yellow F	(Cl Direct Yellow 50)
Durazol Red 2B	(Cl Direct Red 81)
Durazol Violet R	(Cl Direct Violet 51)
Durazol Blue 4R	(Cl Direct Blue 67)

Chlorazol Blue G (Cl Direct Blue 10)-classification unknown-and the Class C Durazol Yellow 6G also penetrate deeply into the fibre and, together with the above dyes, should be used for mats, etc. where good wear properties are needed.

If the goods are intended for outdoor use the colours should not run in the rain nor mark off onto other fabrics when wet. Most dyes when used in pastel shades will meet these requirements but for deeper shades, dyes must be either carefully selected, or after-treated with a cationic fixing agent. The following list includes the more water fast of the dyes investigated and a guide to the need for the use of after treatments is given in Table 4

Durazol Yellow 6G	(Cl Direct Yellow 46)
Chlorazol Scarlet 4B	(Cl Direct Red 23)
Durazol Orange 2G	(Cl Direct Orange 34)
Durazol Green 5G	(Cl Direct Green 28)
Chlorazol Black BV	(Cl Direct Black 19)
Chlorazol Black GF	(Cl Direct Black 22)

These dyes generally penetrate less deeply into the fibre but nevertheless are probably suitable for most purposes. However, although more water fast than the Class A dyes, deep colours will need after-treating. When considering after-treatments it must be remembered that the resultant shade may be different in hue and of lower light fastness than the untreated colour. It is also important to remember that reducing the depth of colour to improve water fastness will also reduce light fastness.

Since only a few of the large number of the direct dyes available have been evaluated, manufacturers may be able to recommend other dyes that penetrate well into the fibre and that have good light and water fastness on sisal. Also, when good light and water fastness is essential, it is worth considering using dyes of the 'Benzo Cuprol'

type offered by Bayer. Some dyes of this type are included in ICl's 'Durazol' and 'Chlorazol' ranges of direct dyes of which Durazol Green 5G, Durazol Blue 4R, Durazol Violet R and Chlorazol Blue G were examples.

For craft workers who are unable to keep a large selection of dyes, Durazol Yellow 6G, Durazol Red 2B and Chlorazol Blue G should produce a wide range of hues when blended. Of the direct dyes which have been examined at TDRI, they are probably the most suitable dyes for this purpose although the colours are not ideal.

Application of dyes

Sisal fibre is best dyed using a liquor to fibre ratio of 20:1. The fibre is placed in the dye liquor at about 50°C and the dyebath is then slowly heated, with stirring, to deposit the colour evenly on the fibre. Finally the fibre is left in the boiling liquor for 60 - 90 minutes to complete the adsorption of the dye and allow it to penetrate into the fibre.

Use of chemical dyeing assistants

Salt (either common salt or Glauber's salt) is used to increase the affinity (see Glossary) between the dye and the fibre. The amount required varies between 2 g/l and 20 g/l depending on the depth of colour. With deep shades the use of extra salt will ensure that as much as possible of the expensive dye exhausts onto the fibre. However, a point is reached where the cost of the salt exceeds the value of the dye saved and dyers will need to experiment to find the optimum quantity of salt.

Soda ash, or sodium carbonate is added to the dye liquor at a rate of 2 per cent on weight of fibre to prevent the dye behaving as an acid dye and thereby building up colour unevenly through residual acidity in the fibre.

A wetting and penetrating agent is added to the dyebath at a rate of about 1 g/l to improve the solubility of the dye and to speed the entry of water into the fibre.

Water

It is better to use soft or rain water in the dyebath since some direct dyes react with the calcium and magnesium in hard water to form a scum on the fibre. The addition of soda has a similar effect. The use of a sequestering agent (see Glossary) is therefore recommended if soft water is not available.

Recipe for producing a Grey Shade on 3.5 Kg of Sisal

This recipe uses an exhaust method . Very experienced dyers may be able to reduce chemical costs by using an alternative technique known as the standing bath.

Materials and equipment required
Sisal		3.5 kg
Durazol Green 5G	35 g	(1 per cent on fibre)
Durazol Red 2B	7 g	(0.2 per cent on fibre}
Common salt (sodium chloride)	350 9	(5 9/l)
Soda ash	70 9	(2 per cent on fibre)
Synperonic BD	70g	(1 g/l)
Spring balance
Laboratory balance
Beakers (or similar containers)	5
Buckets		2
Dye vat		(minimum capacity about 80 litres)
Stirring rods	1 short for use in buckets; 1 long for use in dye vat
Water		70 litres
Drying lines		(Liquor ratio 20:1)
Fuel
Burner

Preparing for dyeing
1. Weigh out 3.5 kg of sisal.
2. Weigh out in beakers and place to one side the following:
35 g	Durazol Green 5G
7 g	Durazol Red 2B
70 g	Soda ash
350 g	Common salt
70 g	Synperonic BD

3. Pour 20 litres of water (about one-third of the total needed) into the dyebath and start heating it to save time later. A dipstick is useful for measuring the
water.

4. Take about three-quarters of a bucket of water from the dyebath (be careful not to scald yourself since the water may be hot).

5. Empty the weighed dye powders into a clean dry bucket (taking care not to breathe the dust).

6. Using a little of the water taken from the dyebath at step 4 rinse the beakers which contained dye. Do not throw away the rinsings since they contain some of the weighed dye.

7. Add about 80 ml of water taken from the dyebath at step 4 to the dye powder.

8. Mix the dye powder to a smooth paste with the water (there should be no lumps).

9. Pour the rinsing water from the emptied dye beakers into the dye paste. Continue rinsing the beakers with water taken from the dyebath at step 4 until they are clean.

10. Add water taken from the dyebath at step 4 to the pasted dye (use about half a bucket but save some for rinsing). Stir until all the dye powder is dispersed into the water.

11. Pour the dye dispersion into the dyebath. Then rinse the bucket into the dyebath using water taken from the dyebath at step 4.

12. Rinse the Synperonic BD into the dyebath using the remainder of the water taken at step 4.

13. Stir the dyebath well then bring it to the boil with occasional stirring. Boil it for a few minutes to dissolve the dye.

14. Bring the dyebath to its full volume (70 litres) by adding 50 litres of cold water. Stir well.

The bath will now be at about 50°C-the maximum temperature at which dyeing should be started.

Dyeing

1. Put the sisal in the dyebath and press it below the surface of the dve liquor.

2. Slowly heat the dyebath, with stirring, taking about 30 minutes to reach the boil. Stir carefully to avoid tangling of the fibre.

3. Still with frequent stirring, sprinkle the salt into the boiling liquor taking about 15 - 30 minutes to add it all. Use small amounts at first, then larger amounts.

Check the water level with the dipstick periodically and replace water lost through evaporation.

4. Leave the fibre in the boiling liquor for a further 45 - 60 minutes with occasional stirring.

Periodically check the water level and replace the water lost through evaporation.

Do not be tempted to remove the fibre earlier since penetration of dye into the fibre will be inadequate.

5. Remove the fibre from the dyebath. (Since the fibre may adsorb more dye from a cooling liquor it may be beneficial to leave the fibre in the liquor until it has cooled to about 60°C).

6. Rinse the fibre in cold running water until the rinsing water remains free from colour. (See below for after-treatment if necessary).

7. Hang the fibre in the shade to dry.

After-treatment

Using commercial cationic dye fixing agents

The water fastness of most direct dyes can be improved by after-treatment. These dyes have an affinity for and are able to complex (see Glossary) with basic or 'cationic' (see Glossary) substances. The molecules (see Glossary) of the complex are larger than those of the dye and therefore are held more firmly within the fibre structure. Most dyestuff manufacturers market a range of chemicals, known as cationic fixing agents (e.g. Matexil FC-PN, Levogen WW) specifically for improving water fastness. They are used after the dye has been applied to the fibre. However, the colour produced is often less light fast than that of the untreated dye.

Table 4 lists the dyes already mentioned and indicates at which depth of shade the use of after-treatments is beneficial.

Table 4: Shades of direct dyes needing after treatment

ICI recommend their Matexil FC-PN for the after-treatment of direct dyes and Bayer recommend Levogen WW or one of their other Levogen brands. However, craft workers using reactive dyes might well find that the after-treatment agents recommended for reactive dyes are also suitable for direct dyes.

The after-treatments are applied to the still wet, dyed and rinsed fibre by a process similar to exhaust dyeing. The agent is mixed into sufficient water to give a liquor to fibre ratio of 20:1 and the fibre is immersed in the solution and stirred. The bath is then warmed to about 50°C, with stirring, at which temperature the fibre is treated. for a further 30 minutes. The fibre is then removed from the bath, rinsed in clean water until free from surplus chemical, and hung to dry.

The amount of agent needed in the bath varies from dye to dye and, also, with the depth of colour. In general. 0.5 - 2 per cent on the weight of air-dry fibre is used, with the larger amount being used mainly for deep colours which bleed heavily.

An example procedure, using 1 per cent on weight of fibre of after-treating agent on 3.5 kg (air-dry weight of fibre: i.e. weight before dyeing) of freshly-dyed fibre, is:

1. Read section on Safety precautions and first aid treatment. Weigh out 35 9 of Matexil FC-PN (1 per cent of 3.5 kg) into a beaker or other suitable vessel.

2. Pour 70 litres of cold water into the empty, clean dyeing vessel, or other suitable container.

3. Rinse the 35 9 of Matexil FC-PN into the 70 litres of water and stir well.

4. Take the 3.5 kg (air-dry weight) of freshly-dyed wet fibre and ensure that it is rinsed free from loose colour (the presence of loose colour on the surface of the fibre will lead to poor rub fastness of after-treated shades).

5. Place the wet fibre in the Matexil solution and stir well for about 5 minutes.

6. Slowly heat the after-treatment liquor to 40 - 60°C (just too hot to touch) with frequent stirring.

7. Remove the heat and leave the fibre in the hot liquor for 20 minutes with occasional stirring.

8. Remove the fibre from the liquor and rinse well in clean cold water.

9. Hang the fibre in the shade to dry.

10. Pour the used liquor away where it will not contaminate food or water.

Using copper sulphate

Certain dyes will form complex molecules with copper. These dyes can be aftertreated with copper sulphate to improve not only their water fastness, but their light fastness also. Dyestuff manufacturers often market these dyes as a separate range (e.g. gayer's 'Benzo Cuprol' dyes) but this is not always the case. Therefore it is recommended that the dye supplier is consulted as to whether the dyes being used will respond to this treatment, or that some experimental dyeing and after-treating is carried out.

The amount of copper sulphate needed is, as with cationic after-treatments, dependent on the dye and its depth of shade. However, Bayer recommend that between 1 per cent and 3 per cent (on the air-dry weight of fibre) of the blue, crystalline copper sulphate is used with 'Benzo Cuprol' dyes.

The dyed, rinsed, still wet fibre is placed in a fresh bath containing the appropriate amount of copper sulphate and 0.5 - 1 per cent (on the air-dry weight of fibre) of 60% acetic acid. This bath is heated to 80 - 90°C (near the boil) at which temperature the fibre is treated for a further 20 - 30 minutes. The fibre is then removed from the bath and rinsed well with cold water. In order to ensure uniform treatment, the after-treatment bath must be stirred.

Acid dyes

Introduction

Acid (or anionic) dyes have a coloured component carrying a negative electrical charge which is attracted by positive charges on the fibre. Basic (or cationic) dyes have a positive charge and therefore must not be mixed with acid dyes since they will neutralise each other to form an insoluble complex.

The acid dyes were designed for use on wool. However, there are many which will dye sisal in attractive, bright and inexpensive colours. In light fastness they vary between high and very low. Although they tend to be less light fast on sisal than on wool, craft workers should have no difficulty in finding acid dyes of adequate light fastness. However, the brighter colours tend to be least light fast.

Generally the water fastness of acid dyes is not very high. However, the 1:2 metal complex dyes (see Glossary), developed to give better fastness on wool, also give shades of good light and water fastness on sisal. These dyes have similar properties to a group of acid dyes known as the 'Acid Milling dyes' which have better than average water fastness for the class. However, they penetrate the fibre less readily than do ordinary acid dyes. Also, with the 1:2 metal complex dyes colours tend to be less bright than with ordinary acid dyes.

Manufacturers' trade names

Acid dyes are made by a large number of manufacturers*; some examples of names used are:

'Lissamine', 'Nylomine', 'Coomassie' and 'Carbolan' (ICI)
'Acilan', 'Alizarine', 'Supramin' end 'Supranol' (BAY)
'Erio', 'Erionyl', end 'Eriosin' (COY)

The 1:2 metal complex dyes are less widely manufactured and are often marketed in ranges separate from ordinary acid dyes. Examples of ranges which are composed largely of 1:2 metal complex dyes are:

'Irgalan'(CGY)
'Isolan' (BAY)
'Lanasyn' (S)
'Ortolan'(BASF)
'Remalan' (HOE)

Choice of dyes

Most acid dyes penetrate well and, provided that light and water fastness properties are not of prime importance, the craft worker has a wide variety of dyestuffs from which to choose. However, if these properties are important, it is suggested that the craft worker uses the following dyestuffs, although the list is by no means comprehensive:

Supranol Fast Yellow 4GL	(Cl Acid Yellow 79)
Supranol Fast Scarlet GN	(Cl Acid Red 85)
Supranol Fast Brown 5R	(Cl Acid Orange 51)
Supranol Blue BL	(Cl Acid Blue 59)
Supranol Blue GL	(Cl Acid Blue 102)
Supranol Brown B	(Cl Direct Brown 30)
Supramin Yellow RN	(Cl Acid Yellow 143)
Alizarin Fast Grey BBLW	(not listed in the Colour Index)
Nylomine Yellow A-G	(Cl Acid Yellow 135)
Coomassie Green G	(Cl Acid Green 25)

When used in pale shades, the water fastness of these dyes will be adequate for most craft purposes. When good light and water fastness are more important than good penetration, the use of 1:2 metal complex dyes is recommended. Many 'Isolan' dyes give good fastness properties on sisal; however, when applied in heavy shades their water fastness is generally inferior to that of the reactive dyes or after-treated direct dyes.

Dyes based on triaryl methane are the best choice when the sole requirement is brightness of shade. Bayer's 'Acilan' ayes are of this type and examples of similar products are:

Coomassie Violet R	(Cl Acid Violet 17)
Coomassie Blue FF	(Cl Acid Blue 15)
Lissamine Turquoise AN	(Cl Acid Blue 7)
Lissamine Green G.	(Cl Acid Green 3)

Most of these dyes tend to be of violet, green or blue hues but there are many bright reds, oranges and yellows amongst the acid dyes. Since these bright acid colours often have poor light and water fastness, craft workers who need light and water fast bright colours should consider using the reactive dyes.

Application of dyes

Use of chemical dyeing assistants

Choice of acid

When using acid dyes an acid is generally added to the dyebath in order to create an affinity (see Glossary) between the fibre and the dye. Often the acid is added at the start of dyeing, but adding it in portions throughout the dyeing can control exhaustion and thus assist levelling.

The three acids usually employed are acetic acid, formic acid and sulphuric acid. The type and strength of acid are usually given in dyeing instructions. The experienced dyer will adapt the recipe according to the acid available-however, a weak acid cannot be used in place of a stronger one.

Some dyes can only be applied using a strong acid, such as sulphuric. This acid is corrosive and unpleasant to handle. It is also non-volatile and traces of acid which remain on the fibre will subsequently cause tendering of sisal. Dyestuffs which have to be applied from a stronqly acid bath should therefore be avoided. If. however. there is no acid other than suiphuric available, the craft worker should steep the dyed fibre in a bath of sodium acetate before drying-this converts the non-volatile sulphuric acid into acetic acid.

Formic acid, being stronger than acetic acid but less corrosive than sulphuric acid and volatile, is recommended for general use. Between 0.5 per cent and 5 per cent on the air-dry weight of the fibre of the 85% strength acid is used in the dyebath.

For some dyes the weaker acetic acid is sufficiently strong and 2 per cent on the airdry weight of fibre of the 6096 strength acid is recommended for use with the 1:2 metal complex dyes (e.g. Bayer's 'Isolan' dyes).

Wetting and penetrating agent

The wetting and penetrating agent is added to the dyebath at a rate of about 1 g/l to improve the solubility of the dye and to speed the entry of water into the fibre.

Recipe for producing a pale olive green shade on 2.5 kg of sisal

This recipe is based on an exhaust method. Experienced dyers may be able to reduce chemical costs by using an alternative technique known as the standing bath. With the 1:2 metal complex acid dyes (e.g. 'Isolan' ayes) it is preferable to commence dyeing in a neutral bath and add acid later. This technique, which assists penetration and levelling of the dye, cannot be used with a standing bath because of residual acidity left from previous batches of fibre.

Materials and equipment required

Sisal		2.5 kg
Supramin Yellow RN	17.5 g	(0.7 per cent on fibre)
Supranol Blue BL	1.25 g	(0.05 per cent on fibre)
Synperonic BD	50 g	(1 g/l)
Formic acid (85%)	100 g	(4 per cent on fibre)

Spring balance
Laboratory balance
Beakers (or similar containers)	4
Buckets	2
Dye vat	(minimum capacity about 70 litres)
Measuring cylinder or dipstick
Stirring rods	1 short for use in buckets; 1 long for use in dye vat
Water	50 litres (Liquor ratio 20:1)
Drying lines
Fuel
Burner

Preparing for dyeing

1. Weigh out 2.5 kg of sisal.

2. Weigh out in beakers and place to one side the following:

17.5 g	Supramin Yellow RN
1.25 g	Supranol Blue B L
50 g	Synperonic BD
100 g	Formic acid (85%)

3. Pour 15 litres of water (about one third of the total needed) into the dyebath and start heating it to save time later. A dipstick is useful for measuring the water.

4. Take about three-quarters of a bucket of water from the dyebath (be careful not to scald yourself since the water may be hot).

5. Empty the weighed dye powders into a clean dry bucket (taking care not to breathe the dust).

6. Using a little of the water taken from the dyebath at step 4 rinse the beakers which contained dye. Do not throw away the rinsings since they contain some of the weighed dye

7. Add about 40 ml water taken from the dyebath at step 4 to the dye powder.

8. Mix the dye powder to a smooth paste with the water (there should be no lumps).

9. Pour the rinsing water from the beakers which contained dye into the dye paste. Repeat rinsing of the beakers with water taken from the dyebath at step 4 until they are clean.

10. Add water taken from the dyebath at step 4 to the pasted dye (use about half a bucket but save some for rinsing). Stir until all the dye powder is dispersed into the water.

11. Pour the dye dispersion into the dyebath. Then rinse the bucket into the dyebath using water taken from the dyebath at step 4.

12. Rinse the Synperonic BD into the dyebath using water taken at step 4.

13. Stir the dyebath well then bring it to the boil with occasional stirring. Boil it for a few minutes to dissolve the dye.

14. Using the remaining water taken at step 4 rinse the acid into the dyebath. (If the acid is to be added portion-wise later to assist levelling just add the remaining water to the dyebath).

15. Bring the dyebath to its full volume (50 litres) by adding 35 litres of cold water. Stir well.

The bath will now be at about 50°C-the maximum temperature at which dyeing should be started.

Dyeing

1. Put the sisal in the dyebath and press it below the surface of the dve liquor.

2. Slowly heat the dyebath, with stirring, taking about 30 minutes to reach the boil. Stir carefully to avoid tangling of the fibre.

3. Leave the fibre in the boiling liquor for a further hour with occasional stirring.

If acid has been saved to assist levelling add it to the bath portionwise throughout the period at the boil.

Check the water level with the dipstick periodically and replace water lost through evaporation.

Do not be tempted to remove the fibre earlier since penetration of dye into the fibre will be inadequate.

4. Remove the fibre from the dyebath. (Since the fibre may adsorb more dye from a cooling liquor it may be beneficial to leave the fibre in the liquor until it has cooled to about 60° C).

5. Rinse the fibre in cold running water
6. Hang the fibre in the shade to dry until the rinsing water remains free from colour.

Basic dyes

Introduction

Basic (or cationic) dye molecules have a coloured component carrying a positive electrical charge which is attracted by negative charges on the fibre. Basic dyes must not be: (i) mixed with the negatively charged acid dyes since they will neutralise each other to form an insoluble complex; or (ii) used under alkaline conditions since many of the dyes will decompose to form the colourless dye base which is insoluble in water.

The basic dyes, like the acid dyes, unite chemically with the fibre. They do not take directly on cotton but they do on ligno-cellulosic fibres such as sisal, jute and coin For brightness and clarity of colour the basic dyes cannot be matched by any other class of dyestuff. Also, since the dyestuffs produce intense colours, quite small quantities of dye will produce deep hues.

Although they produce bright colours cheaply, the light and water fastness properties of the colours are generally poor and for many textile purposes these dyes have been largely displaced by the more modern acid, direct, and reactive dyes.

Nowadays the traditional basic dyes are mainly used on non-durable items. However, new basic dyes specifically developed for acrylic fibres are appearing on the market. Some of these dyes have light fastness properties on sisal that are superior to those obtained with traditional basic dyes such as Safranine, Magenta, Methyl Violet and Methylene Blue. Although water fastness tends to be low it can be improved substantially by the use of a 'back-tanning' after-treatment.

Manufacturers' trade names

A wide variety of names, often ending in 'cryl' , are used for dye ranges of basic dyes*, e.g.:

'Astrazon' (BAY)
'Basacryl' (BASF)
'Maxilon' (COY)
'Sandocryl' (S)
'Synacril' (ICI)

Choice of dyes

The following observations are based on limited trials on ICl's 'Synacril' ayes, gayer's 'Astrazon' dyes, Sandoz's 'Sandocryl' ayes and Dupont's 'Sevron' dyes:

Yellow

Astrazon Yellow 7GLL (Cl Basic Yellow 21) and Yellow 8GL (Cl Basic Yellow 13), Sandocryl Brilliant Yellow B-5GL (Cl Basic Yellow 61), and Synacril Yellow 8G (Cl Basic Yellow 13) give clear yellow shades. These dyes have fairly good light fastness on sisal but, when wet, they tend to mark off onto sisal, cotton and wool. In this respect the dyes have similar properties to many of the untreated direct dyes.

Sevron Yellow 3RL (Cl Basic Yellow 15) and Astrazon Golden Yellow GL (Cl Basic Yellow 28) give more of an orange hue. Of these the Synacril Yellow is the most orange and the most water fast, but it is only in the paler shades that it ranks amongst the better dyes for sisal. The Sevron dye is the least light fast but both dyes give light fastness ratings of a high order. Possibly blends of these dyes with the pure yellow dyes mentioned earlier will give a wide range of yellow hues with good light and water fastness properties with suitable after-treatment. However, there are reddish yellows of high light fastness available as single dyestuffs, e.g. Sandocryl Golden Yellow B-GRL (Cl Basic Yellow 82) and Sandocryl Yellow BLE (Cl Basic Yellow 56).

Orange

Only Astrazon Orange 3RL (Cl Basic Orange 27) of the available orange dyes has been examined. This dye is of a reddish orange hue and has high light fastness. Possibly blends of this dye with one of the pure yellows mentioned earlier will give a wide range of orange hues with moderate fastness properties. The dye has fair fastness to water.

Red

The basic reds are, in general, less light fast than the yellow and orange dyes already mentioned.

Astrazon Red RL (Cl Basic Red 25) has fairly good light fastness but poor water fastness. It is an orangish red and not particularly bright. This dye will be useful for mixing with yellow to make orange but it is doubtful that it will make satisfactory purples when mixed with blue. Astrazon Red F3BL (Cl Basic Red 22) and Astrazon Brilliant Red RTL (not listed in the Colour Index) are more appropriate colours for mixing with either yellow or blue, and are only marginally less light fast than the Astrazon Red RL.

Bright, magenta coloured dyes such as Sandocryl Brilliant Pink B-5B (Cl Basic Red 75) and Astrazon Red 6B (Cl Basic Violet 7) have low light fastness but they may be found to be a little better than traditional basic dyes. Sandocryl Brilliant Red BF (Cl Basic Red 27) is a little more light fast but is less blue than magenta.

Other reds evaluated include some with moderate fastness to light but are in general dull colours. These include Synacril Red 2G (Cl Basic Red 18:1), Astrazon Red GTL-N (Cl Basic Red 18:1), Astrazon Red 5BL (Cl Basic Red 24) and Astrazon Red BBL (Cl Basic Red 23).

Blue

Many of the blue dyes examined have only moderate light or water fastness- Astrazon Blue 3RL (Cl Basic Blue 47) and Astrazon Blue 5GL (Cl Basic Blue 45) being the most promising. Of these the Blue 5GL is the better colour for blending but the Blue 3RL is a stronger colour and has slightly better light fastness. Astrazon Blue 3RL will be suitable for producing purple by mixing with red.

Other dyes examined include Synacril Blue R (Cl Basic Blue 22), Astrazons Blue RL (Cl Basic Blue 46) and Blue FGL (Cl Basic Blue 22), and Sandocryl Brilliant Blue B-BLE (Cl Basic Blue 77). Of these, Astrazon Blue RL cannot be recommended for sisal on account of poor colour strength.

Green

Only Sandocryl Brilliant Green B-NLE (Cl Basic Green 12) has been examined. This gives a weak colour of poor fastness. Astrazon Blue 5GL or Sandocryl Brilliant Blue B-BLE blended with a pure yellow dye may produce greens with slightly better light fastness. The red component of Astrazon Blue 3RL may give rise to dull green in blends with yellow.

Craft workers wishing to use the new basic dyes should base their shade range on Synacril Yellow 8G (or Astrazon Yellow 8GL), Astrazon Red F3BL (or Astrazon Brilliant Red RTL) and Astrazon Blue 5GL (or Sandocryl Brilliant Blue B-BLE). Blending of these dyes with others of similar light fastness properties should produce a fairly wide range of shades with moderately good light fastness. A back-tanning after-treatment may be needed to obtain satisfactory fastness to water.

Only a few of the wide range of available basic dyes have been evaluated. There may well be other suitable dyes included either in the ranges evaluated, or those offered by other dyestuff manufacturers.

Application of dyes

Use of chemical dyeing assistants

Acid

Acid (usually acetic) is used in the dyebath:

(i) To prevent precipitation of the dye base. Tap, spring and river water is usually alkaline and, as there is some risk of the free dye base precipitating in the dyebath, the water used to prepare the dye liquor must be neutralised with acid (e.g. acetic acid) before introducing the dyestuff. The acid is added with stirring until the water causes blue or neutral litmus paper to just turn red when dipped. Litmus paper can be purchased from some pharmacies.

(ii) Jo help dissolve the dye. If water alone is used a sticky tar is sometimes formed.

(iii) Jo retard exhaustion of the dye. The affinity between basic dyes and the material being dyed is usually so strong that the dye deposits too rapidly for the dyer to obtain even distribution of the dyestuff. By adding acid to the dyebath adsorption of the dye is slowed down enabling the dyer to control the dyeing. More acid is used with pale colours since they are more difficult to level than deep colours.

Wetting and penetrating agent

A wetting and penetrating agent is added to improve the solubility of the dye and to speed the entry of water into the fibre.

Recipe for producing a lime green shade on 1.5 kg of sisal
This recipe is based on the exhaust method. Extremely competent dyers may be able to reduce chemical costs by using an alternative technique known as the standing bath.

Materials and equipment required

Sisal		1.5 kg
Astrazon Yellow 7GLL	28.5 g	(1.9 per cent on fibre)
Astrazon Blue 3RL	1.5 g	(0.1 per cent on fibre)
Synperonic BD	30 g	(1 g/l)
Acetic acid (30%)	60 g	(4 per cent on fibre)
Spring balance
Laboratory balance

Beakers (or similar containers)	5
Buckets	2
Dye bath	(minimum capacity about 50 litres)
Measuring cylinder
Stirring rods	1 very short for beakers; 1 short for bucket,
	1 long for bath
Water	30 litres (Liquor ratio 20:1)
Drying lines
Fuel
Burner

Preparing for dyeing

1. Weigh out 1.5 kg of sisal.

2. Weigh out in beakers and place to one side the following: 28.5 9 Astrazon Yellow 7GLL 1.5 9 Astrazon Blue 3RL 30 9 Synperonic BD 60 9 Acetic acid (30%)

3. Pour 10 litres of water (about onethird of the total needed) into the dyebath and start heating it to save time later. A dipstick is useful for measuring the water.

4. Take about half a bucket of water from the dyebath (be careful not to scald yourself since the water may be hot).

5. Empty the weighed dye powders into a clean dry bucket (taking care not to breathe the dust). Put the beakers to one side-they must be rinsed later.

6. Dilute the acetic acid to 15% strength by pouring 60 mls of water into a beaker then add carefully, with stirring, the 60 9 of acid.

7. Pour about 40 ml of the diluted acid onto the dye powders in the bucket.

8. Mix the dye powders to a smooth paste with the acid (there should be no lumps). Then stir more acid into the paste until about half the acid remains.

9. Wet the beakers which contained dye with a little of the diluted acid then rinse them with water taken from the dyebath at step 4. Add the rinsings to the dye paste.

Continue rinsing the beakers with acid and water until they are clean -save some acid to rinse the bucket later.

10. Add more water taken from the dyebath at step 4 to the dye paste and stir well to disperse the dye powders. Save some of the water to rinse the bucket later.

11. Whilst stirring the dyebath pour in the dye dispersion.

12. Rinse the bucket with a little of the water taken from the dyebath at step 4. Add the rinsings to the dyebath then wet the bucket with some of the remaining acid solution and rinse with water.

Continue rinsing with acid and water until the bucket is clean. Pour any remaining acid into the dyebath but save some water.

13. Using the remainder of the water taken from the dyebath at step 4, rinse the Synperonic BD into the dyebath.

14. Stir the dyebath well then bring it to the boil with occasional stirring. Boil it for a few minutes to dissolve the dye.

15. Bring the dyebath to its full volume (30 litres) by adding 20 litres of cold water. Stir well.

The dyebath will now be at about 50°C-the maximum temperature at which dyeing should be started.

Dyeing

1. Put the sisal in the dyebath and press it below the surface of the dye liquor.

2. Slowly heat the dyebath, with stirring, taking about 30 minutes to reach the boil. Stir carefully to avoid tangling of the fibre.

3. Leave the fibre in the boiling liquor for a further 60 - 90 minutes stirring frequently at first, then occasionally.

Do not be tempted to remove the fibre from the dyebath earlier since penetration of dye into the fibre will be inadequate.

Check the water level with the dipstick periodically and replace water lost through evaporation.

4 Remove the fibre from the dyebath.

Note: the fibre may adsorb more dye if:

(i) it is left in the liquor whilst it cools.

(ii) the dyebath is neutralised with, for example, soda ash towards the end of dyeing. The bath must not be made alkaline.

5. Rinse the fibre in cold running water until the rinsing water remains free from colour. (See below for after-treatment if necessary).

6. Hang the fibre in the shade to dry.

After-treatment

Water fastness can be improved by after-treatment ('back-tanning') with tannic acid and tartar emetic (potassium antimony tartrate) as follows:

1. Steep the freshly-dyed fibre in a solution containing 1 9/l of tannic acid and leave in the solution for 30 minutes at room temperature. Use a liquor to fibre ratio of 20:1 (for 1.5 kg of fibre use 33 9 of tannic acid dissolved in 30 litres of water).

2. Remove the fibre from the solution and shake the excess tannic acid from it.

3. Immerse the fibre in a solution containing 0.3 g/l of tartar emetic using a liquor ratio of 20:1 (for 1.5 kg of fibre use 9 9 of tartar emetic dissolved in 30 litres of water). Leave in the solution for 30 minutes.

4. Remove the fibre from the solution and rinse it in a drum of cold water.

5. Place the fibre on a line to dry.

Safety note: Tartar emetic is poisonous. Use with great care (see Safety precautions and first aid treatment).

Disperse dyes

Introduction

The disperse dyes were developed for man-made fibres (such as cellulose acetate) which do not take up ionic dyes (see Glossary). The dyes are in the form of a suspension of particles which, for reasons not fully understood, are adsorbed onto the surface of ligno-cellulosic fibres such as sisal, abaca and fique. On these fibres they are easy to use and, where good penetration is needed, are the best choice of dyestuff. There are, however, some disadvantages in using disperse dyes. Of these the most important to the craft worker are:

(i) Many of the dyes are not fast to heat. When ironing or when blocking hats, some of the dyes vaporise, staining adjacent materials and reducing the depth of colour on the fibre. However, this is important only when hot processes are used after dyeing.

(ii) Sisal has a low capacity for adsorbing disperse dyes sometimes giving only pastel shades.

(iii) Only a few disperse dyes give good light and water fastness on sisal.

There is no simple method of overcoming the poor light and water fastness of the dyes but where hot processes are used after dyeing, loss of colour can sometimes be compensated for by using extra dye.

Disperse dyes will probably only be obtainable directly from the dyestuff manufacturers or their agents. Some multi-purpose dyes (see Glossary) include disperse dyes in blends with other classes of dyes.

Manufacturers' trade names

Many dyestuff manufacturers* market a range of disperse dyes, some examples are:

'Cibacet' (COY)
'Dispersol' (ICI}
'Resolin' (BAY)
'Artisil' end 'Foron' (S)

The ICI 'Procinyl' range of dyes are reactive disperse dyes for nylon but they can also be used as ordinary disperse dyes and are included here.

Choice of dyes

Since many of the limited number of disperse dyes investigated gave poor light and water fastness on 'straws" only a few selected dyes were evaluated on sisal. Of these the following could form the basis of a shade range:

Yellow

Procinyl Yellow G (Cl Reactive Yellow 5) has moderately good light and water fastness properties and builds up to fairly deep shades. Its fastness properties are similar to the reds and blues recommended for blending (see later). Dispersol Yellow AG (Cl Disperse Yellow 3), although of similar light fastness, tends to stain cotton, wool and sisal heavily when wet.

Artisil Brilliant Yellow 6GFL (Cl Disperse Yellow 49) and Foron Brilliant Yellow 5GL (Cl Disperse Yellow 126) both build up to deep, bright greenish yellows suitable for blending. They have better light fastness than the Procinyl Yellow and stain cotton less deeply when wet. However, the deeper shades tend to mark off onto wool a little more heavily than the Procinyl dye.

Resolin Yellow GRL (Cl Disperse Yellow 66) and Artisil Yellow FL (Cl Disperse Yellow 42) also have high light fastness and moderately good water fastness, but do not build up to such intense colours as the dyes just mentioned.

Red

Trials to date have failed to identify a dye which will produce intense, colour fast, bright magenta hues: the range of fast colours that craft workers will be able to produce will therefore be restricted. However, Resolin Brilliant Red BLS (Cl Disperse Red 159) comes nearest in its properties. Although Dispersol Red B-2B (Cl Disperse Red 60) is similar in hue and fastness properties it only builds up to a pale pink colour and it would therefore be wasteful to use more than 0.5 per cent on weight of fibre of this dye. Another promising alternative is Dispersol Red C-B (Cl Disperse Red 91). This also gives weak, fast colours but is less blue than magenta.

In order to extend their shade range it is suggested that craft workers add one of the following colours: Foron Yellow Brown S-2RFL (Cl Disperse Orange 30) or Foron Brilliant Orange S-FL (Cl Disperse Orange 96). These are oranges with good light and water fastness which could be used to blend reddish yellows. Other potentially useful dyes either as single dyes or in blends include:

Foron Brilliant Red S-RGL	(Cl Disperse Red 202)
Foron Brilliant Scarlet S- RL	(Cl Disperse Red 210)
Foron Scarlet S-3G FL	(Cl Disperse Red 54)
Foron Rubine S-2G FL	(Cl Disperse Red 167)
Dispersol Scarlet C-G	(not listed in the Colour index)
Resolin Red B RL	(Cl Disperse Red 134)

Blue

Of the few dyes investigated, Dispersol Blue DOG (Cl Disperse Blue 296) was closest to the primary hue of cyan. Although a weak dye, it builds up to a medium depth of colour using about 4 per cent dye on weight of fibre. It has good water fastness and although its light fastness is a little lower than that of the suggested red and yellow dyes it could nevertheless be a useful dye for blending.

Artisil Blue BGL (Cl Disperse Blue 73) is a stronger blue with better light fastness and good water fastness. Although a greener blue would be preferable, it will nevertheless produce a useful range of fast colours. An alternative blue of similar qualities is Cl Disperse Blue 56 (Dispersol Blue BR, Resolin Blue FBL and other equivalents).

Trials which led to the above selection of dyes were not exhaustive and it is recognised that there may well be other disperse dyes which give light and water fast colours on sisal.

Application of dyes

Use of chemical dyeing assistants

Unlike other classes of dyes only water and the dyestuff are needed when applying these dyes. However, a wetting agent (e.g. 1 9/l Synperonic BD) in the dyebath can be used to improve the stability of the dye suspension and to assist the transfer of dye to the fibre.

Recipe for producing a lilac shade on 3 kg of sisal

This recipe is based on the exhaust method . The initial preparation of the dye liquor needs special care as the method for dispersing the dye into water differs from the methods used for dissolving dyes of other classes. Extremely competent dyers may be able to reduce chemical costs on dyes that do not exhaust well by using an alternative technique known as the standing bath.

In the authors' experience, the disperse dyes can be used together with acid or basic dyes to blend preferred hues. The dyeing method used with such blends should conform to that used with acid or basic dyes, and the disperse dyestuff should be dispersed into water separately as described here before it is added to the dyebath. There is no apparent reason why disperse dyes should not be used with direct dyes also.

Materials and equipment required

Sisal	3 kg
Dispersol Blue BR	18 g	(0.6 per cent on fibre)
Dispersol Red B-2B	12 g	(0.4 per cent on fibre)
Synperonic BD	60 g	(1 g/l)
Spring balance
Laboratory balance

Beakers (or similar containers)	3
Buckets	2
Dye vat	(minimum capacity about 90 litres)
Measuring cylinder
Stirring rods	1 short for use in bukets, 1 long for use in the dye vat
Water	60 litres (Liquor ratio 20:1)
Drying lines
Fuel
Burner

Preparing for dyeing

1. Weigh out 3 kg of sisal.

2. Weigh out in beakers and place to one side the following: 18 9 Dispersol Blue BR 12 g Dispersol Red B-2B.

3. Pour 60 litres of water into the dyebath and heat it to 50°C. A dipstick is useful for measuring the water.

4. Take about three-quarters of a bucket of the warm water from the dyebath.

5. Pour 300 ml of the warm water taken from the dyebath into another bucket.

6. Stir the 300 ml of water in the bucket and sprinkle the weighed dye powders into the moving water (be careful not to breathe the dust). Do not continue stirring.

7. Using a little of the water taken from the dyebath at step 4 rinse the beakers which contained dye. Do not throw away the rinsings since they contain some of the weighed dye.

8. With dye 'powders' periodically stir the mixture in the bucket over about the next 10 minutes. With 'grains' stir the mixture for the first time after 5 minutes, then periodically. The mixture is ready when no dye settles to the bottom of the bucket.

9. Pour rinsing water from the emptied dye beakers into the dye mixture. Continue rinsing the beakers with water taken from the dyebath at step 4 until they are clean.

10. Add water taken from the dyebath at step 4 to the dispersed dye (use about half a bucket but save some for rinsing) and stir.

11. Pour the dye dispersion into the dyebath. Then rinse the bucket into the dyebath using water taken from the dyebath at step 4.

12. Rinse the Synperonic BD into the dyebath using the remainder of the water taken at step 4.

13. Stir the dyebath well. (Since disperse dyes do not dissolve the bath will remain cloudy).

Dyeing

1. Put the sisal in the dyebath and press it below the surface of the dye liquor.

2. Slowly heat the dyebath, with stirring, taking about 30 minutes to reach the boil. Stir carefully to avoid tangling of the fibre.

3. Leave the fibre in the boiling liquor for a further hour with occasional stirring.

Check the water level with the dipstick periodically and replace water lost through evaporation.

Do not be tempted to remove the fibre earlier since penetration of dye into the fibre will be inadequate.

4. Remove the heat from the dyebath and leave the fibre in the liquor until it has cooled to 50°C.

5. Remove the fibre from the dyebath.

6. Rinse the fibre in cold running water until the rinsing water remains free from colour.

7. Hang the fibre in the shade to dry.