Dyeing of Leaves and Straws: A Handbook for Craft Instructors (NRI) Properties of selected dyes Introduction Guide to tables Key to ratings used in the tables

Dyeing of Leaves and Straws: A Handbook for Craft Instructors (NRI)

Properties of selected dyes

Introduction

From the wide ranges available, a limited selection of dyes was evaluated on iraca straw, jippi-jappa, big thatch, pandanus, vetiver grass and processed coconut leaf. The results for light and water fastness of the colours produced are given in Tables 1 - 4.

In the tables, dyes are listed, where possible, in order of their Colour Index Generic Name (Colour Index Number). Dyes that have not been assigned a Colour Index Generic Name are not listed in the Colour Index (Society of Dyers and Colourists/American Association of Textile Chemists and Colorists, 1982) and information on their availability can be obtained only from their respective manufacturers.

The commercial name of the dye evaluated is given with the Colour Index Generic Name. Those dyes where the commercial name is marked with a dagger were not available at April 1982. Examples of near equivalents of some withdrawn brands are given in Table 5 together with a code name for their respective manufacturers; the full names and addresses are given in the Appendix. Where near equivalents were not available at April 1982 a dagger appears against the Colour Index Generic Name. Information on the availability of dyes was derived from the Co/our Index.

It is emphasised that, unless listed in Tables 1 - 4, the alternative brands given in Table 5 have not been evaluated at TDRI and therefore it cannot be guaranteed that these dyes will give results identical to those obtained from the evaluated brands.

There may be many dyes amongst those not evaluated which will also give good fastness and penetration on straw materials and some manufacturers may be able to give information on the suitability of dyes in their own ranges.

Guide to tables

A useful comparison between dyestuffs can be made only by using samples to produce the same visual depth of colour on the same material, and then evaluating the properties of the resulting colours. In this handbook, fastness ratings are, wherever possible, reported for shades approximating to the 1/3, 1/1 and 2/1 standard depths* illustrated in British Standard BS1006: Section AOI: 1978 Standard depth: matt, a set of pattern cards supplementary to BS1006: 1978 Methods of test for colour fastness of textiles and leather. Fastness ratings for these shades, subsequently referred to as 1/3N, 1/1N and 2/1N, are given in the tables in ascending order of visual depth.

Light fastness was determined using BS1006: 1971 Methods for the determination of the colour fastness of textiles to light and weathering. Water fastness (staining onto cotton and wool) was determined using BS2681: 1961 Method for the determination of colour fastness to water; staining of undyed material of the same type was determined by immersion of a plait, comprising equal weights of dyed and undyed material, in thirty times its weight of cold water for 4 hours then, after drying in air, assessing staining using BS2663: 1961 Grey scale for assessing staining. No attempt has been made to assess change of shade in view of the variation in colour between different batches of material.

In the tables, only the percentage depths of shade (the amount of dye used in the dyebath expressed as a percentage of the weight of air dry straw dyed) which produced the standard visual depths evaluated are given. These represent the standard depths as shown by the example overleaf:

Colour Index Generic Name	Commercial name	Percentage strode
Cl Basic Orange 48	Synacril Yellow R	0.5 (= 1/3N)
	(ICI)	2.0 (= 1/1N)
		5.0 (= 2/1N)
Cl Reactive Yellow 5	Procinyl Yellow G	0.5 (= 1/3N)
	(ICI)	1.0 (= 1/1N)
		2.0 (= 2/1N)

Percentage shades will give an indication of the strength of the dye, e.g. in the example Procinyl Yellow G has two and a half times the colour strength of the Synacril Yellow dye when producing 2/1N depths. This is an important factor when comparing the cost of dyes. However, colour yield is affected by dyebath exhaustion (the Procinyl dye loses its advantage at paler shades, which exhaust more readily), so care should be taken to ensure that each dye is applied under the most appropriate conditions.

When, for practical reasons, it was not possible to evaluate standard depths of shade, symbols (e.g. 1/3N- or 1/1N+ representing shades slightly paler or deeper respectively than standard depths) are used, as in the following example:

Colour Index Generic Name	Commercial name	Percontago strode
Cl Acid Blue 25	Nylomine Blue A - G	1.0 (1/3N +)
	(ICI)	2.0 (1/1N +)
		3.0 (1/2N -)

(Note that if, for example, the 2.0 per cent shade were without a symbol it would be of standard depth (1/1N)).

In the following example [for Cl Acid Green 41: namely Alizarine Cyanine Green 5G (Bayer)] fastness ratings are for a 2.0 per cent shade. However, for staining on undyed big thatch a 3.0 per cent shade was assessed in place of the 2.0 per cent shade.

Percentage shade	Light fastness	Water fastness: staining onto
		Undyed big thatch	Cotton and wool
2.0	XXXXX	XXXXX (3.0%)	XXX

Not all dyes were evaluated at the three standard depths. For example, when a 1/1N shade was of poor light fastness it was clearly unnecessary to evaluate a paler shade. Similarly if a 1/3N shade had poor water fastness it would only be worse at 1/1 N.

Fastness properties and the uptake of dye can be affected by small variations in dyeing technique, in the nature of the substrate, and the environment in which the dyed material is used. Whilst every effort has been made to ensure that the information given in the tables is accurate, it cannot be guaranteed that identical results will always be obtained.

Key to ratings used in the tables

The numerical ratings described in the British Standards for light and water fastness have been expressed as sets of crosses in Tables 1 - 4 (ratings marked with an asterisk (*) have been taken from ICI data sheets). How the numerical ratings relate to the ratings used in the tables is shown below.

Key to light fastness ratings

Numerical rating	Table rating
5 - 6 and above	XXXXX
4 - 5 and 5	XXXX
3 - 4 and 4	XXX
2 - 3 and 3	XX
2 and below	X

The light fastness ratings are mainly for daylight in London. However, for many of the trials it was necessary to use artificial light, either an 'Atlas' carbon are fadeometer or a 'Microscal' mercury/tungsten blended lamp fadeometer. Use of these has been indicated in the tables by the letter 'A' (for Atlas) or 'M' (for Microscal) after the light fastness rating.

Key to water fastness ratings

Numerical rating	Table rating
4 - 5 and 5	XXXXX
4	XXXX
3-4	XXX
3	XX
2 - 3 and below	X

The water fastness ratings are for staining onto adjacent undyed straw of the same type, cotton and wool. Where the test samples underwent significant change in colour (greater than 4 - 5 on the British Standard scale), this has been indicated by the use of letters L (for loss of colour) and C (for change in hue) after the water fastness rating.