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Formulae and Tables - Wood / textbooks for vocational training (GTZ, 122 p.)
	12. Surface Treatment of Wood
		(introduction...)
		12.1. Substances for Surface Treatment
		12.2. Use of the Coating Compositions
		12.3. Examples of Wood Coating Systems

Formulae and Tables - Wood / textbooks for vocational training (GTZ, 122 p.)

12. Surface Treatment of Wood

The surface treatment of wood includes all techniques by which the wood surface is changed in its properties and is coated with liquid substances.

12.1. Substances for Surface Treatment

Substances for deresinification

Name

Composition

Mode of application

solvents

physically acting organic compounds (e.g. acetone)

Apply by means of a sponge or similar, then rub with a clean roll of cloth, wash with warm water.

saponification agent

chemically acting alkaline compounds (e.g. ammonia water)

Apply several times with a sponge, let it rest for 10 - 15 minutes, treat with a brush, neutralize with 10 % acetic acid, then wash with warm water.

Bleaching agents

Name

Mode of application

Use

bleach liquor

Apply solution of 40 g of soda, 50 g of chloride of lime and 30 g of potash in 11 water by means of a brush; after treatment with 5 % warm sodium thiosulphate solution

for bleaching basic consumer goods and especially fir wood; good ventilation of the working rooms necessary.

acetic acid

Apply 5...10 % solution in warm state and wash and brush out thoroughly.

for especially sensitive wood species

potash lye and hydrogen peroxide

Precoat with aqueous potash solution, then apply hydrogen peroxide, finally apply acid neutralizing agent.

suitable for all wood species, removes blue stains, mould stains

sodium hydrogen sulphite

Apply warm 3...5 % solution and then wash thoroughly.

especially suitable for walnut wood

oxalic acid and salt of sorrel

Apply warm 2.5...5 % solution, let it harden and then wash thoroughly.

especially for tanniferous wood; also removal of rust and ink stains - bleaching agent is toxic,

hydrogen peroxide

Apply 30...35 % solution in sufficient quantity.

mainly for low-tanniferous wood species and for coniferous wood species

hydrogen peroxide and ammonia water

Apply hydrogen peroixide solution with 10 % ammonia water by means of a brush.

for quick bleaching of small surfaces

citric acid

Apply 3...5 % solution in a hot state, then wash and brush out well.

for brightening tanniferous wood and for removing stains caused by iron-tanning agent reactions and blue stains

Technique

Properties

Use

plain staining

solutions of heavy metal salts with dyestuffs

only for tanniferous wood species

double staining

Preliminary stains contain tan-like compounds, stains for the second coating contain various metal salts

for low-tanniferous wood; apply the second coating of stain only after the preliminary stain has dried; stains are water-insoluble and resistant to light

wax staining

solutions of metal salts, dyestuffs and wax additives ready for use

for all wood species, not in furniture construction, mat finish effect due to wax portion

Dyestuffs

Name

Properties

Use

water-soluble dyestuffs

made of acid coal-tar dyestuffs and supplementary agents, dissolve in soft water, good penetrability, high light resistance, no or only low water resistance

for all wood species

spirit-soluble dyestuffs

solution of dyestuffs in spirit or in low-binder varnish; good penetrability, low light resistance, low water resistance

for colouring small workpieces, for example in the production of wooden articles or toys

Smoothing agents

Name

Properties

Use

pore filler

pulpy mixture consisting of 40...50 % binder (of drying oils or SH, UP or PUR lacquers) and 50...60 % pore filler powder (heavy spar powder, gypsum, kaolin, quartz powder and others) as well as dyestuffs

for coarse-pored timbers with subsequent lacquer coating; rubbing in of the pore filler by hand with rolls of cloth, after drying removal of the excess filler with a soft, spirit-impregnated cloth

putty

binder as described for pore filler plus fillers and dyestuffs, if required

for smoothing surfaces (e.g. raw chipboards), which afterwards are to be coated with coloured varnishes; only seldom applied by hand with putty knife, mostly with special machines; filled surfaces are to be ground after drying

Coating compositions

Name

Components

Properties

oil varnishes

drying oils and resins; an oil-to-resin ratio of 1:1 to 1:3 yields short-oil varnishes, a ratio of 3:1 to 5:1 yields long-oil varnishes

good adherence of the varnish coating, resistant to climatic influences and moisture as well as chemicals, low hardness of the varnish coating, but high elasticity, slow drying; dyestuffs can be added

cellulose nitrate lacquers (NC lacquers)

collodion cotton, solvents such as toluene, ethyl acetate, butyl acetate and other organic compounds as well as fillers and softeners

combinable with other coating compositions, quick-drying, various levels of gloss possible, lacquer coating is elastic; not moisture-resistant, temperature-sensitive, not resistant to solvents, to oils, acids, lyes and alcohols

alkyd varnishes

alkyd resins, oils and solvents

approximately like oil varnishes, extraordinarily elastic films, high resistance to mechanical influences and climatic influences, water-proof

acid-hardening varnishs (SH-varnishes)

synthetic resins, (urea resin, phenolic resin); solvent, filler and softener, acids as hardener

high adherence, elastic and hard varnish coating, resistant to water, alcohol, spirit and a great number of solvents, temperature-resistant and non-ageing, resistant to mechanical load

polyurethane lacquers (PUR lacquers)

polyacrylate or polyester resins as well as solvents, pigments and fillers, in addition to this isocyanate as secondary component

incompatible with oil and alkyd varnishes, good adherence, hard and abrasion-resistant coatings, resistant to water, alcohol, solvents, variations of temperature

polyester lacquers (UP lacquers)

unsaturated polyester resin (hence UP lacquers), styrene and as hardener of organic peroxides in solvents

mainly for industrial processing, wood components may cause poor adherence (e.g. with the wood species Jacaranda, Iroko, Bété), combination with other kinds of lacquer possible; resistant to water, alcohol and many other substances, resistant to mechanical load and variations of temperature, brittle, cracking under impact load

polyvinyl acetate coating (PVA coating)

polymerized vinyl acetate, softener, fillers, pigments

water-dilutable, therefore not inflammable, not dangerous to health; good opacity, air-permeable, “breathing” of the undersurface possible

Solvents (selection)

Name

Properties

ethyl alcohol

colourless, boiling point 78 °C, inflammable, miscible with water and all usual organic solvents, highly toxic

ethyl acetate

colourless, inflammable, boiling point 77.1 °C, non-miscible with water

acetone

colourless, inflammable, boiling point 56.3 °C, highly volatile, miscible with water and most of the organic solvents

benzene

colourless, very inflammable, boiling point 80.1 “C, non-miscible with water, but miscible with organic solvents, vapours highly toxic

butyl acetate

colourless, inflammable, boiling point 118 °C, non-miscible with water, but miscible with organic solvents

methanol

colourless, inflammable, boiling point 64.7 °C, miscible with water, highly toxic

methylene chloride

colourless, non-miscible with water, boiling point 41.6 °C

toluene

colourless, inflammable, boiling point 110.8 °C, non-miscible with water

xylene

colourless, inflammable, boiling point 139...140 °C, little soluble in water, easily soluble in some organic solvents

12.2. Use of the Coating Compositions

Name

Mode of application

Range of application

oil varnishes

multilayer application by brushing, spraying, rolling or dipping, spread per application:
linseed oil-priming oil 80...120 g/m²
priming paint 120...300 g/m²
coating varnish 100...250 g/m²

fats, slowly drying varnishes for exterior coatings (e.g. windows), short-oil, quicker drying varnishes for interior coatings (e.g. floors)

NC lacquers

multilayer application by brushing, spraying, rolling, casting or dipping 1st spread:
lacquer-to-thinner ratio 3:1
intermediate sanding
2nd spread: ratio 1:1
3rd spread: heavily thinned, rub with polishing cloth
spread - 400 g/m

for furniture and interior varnishing, for toys, arts and crafts, musical instruments

alkyd varnishes

like oil varnishes

coatings with high stability like floors as interior coating and windows and doors as exterior coating; but also as boat varnish (water and weather resistance)

acid-hardening varnishes (SH varnishes)

mixing of the components in the specified ratio in non-metallic vessels; 1 to 3 spreads by brushing, spraying, casting, rolling;
spread £ 140 g/m

for interior coatings which are under stress, but also for exterior coatings; for furniture, sports equipment, windows, doors, parquet and in vehicle construction

polyurethane lacquers (PUR lacquers)

mixing of the two components in the specified ratio; spreading in 1...2 applications by brushing, spraying, casting or rolling;
spread £ 250 g/m²

for interior furnishings, for sports equipment, staircases, parquet, in vehicle construction, as boat varnish and for plastic coatings

polyester lacquers (UP lacquers)

used mainly industrially; several applications according to the kind of spreading; putty, primer and lacquer are applied separately by spraying, casting or rolling;
lacquer spread 80...200 g/m²

especially for living room furniture, but also for other purposes like ship interior work and as boat varnish

polyvinyl acetate coatings (PVA coatings)

thinning with water as much as necessary, several applications according to the desired effect, spreading mainly by brushing;
as PVA coatings are not glossy, a finish coat with oil or alkyd varnish is applied on the PVA priming coat, if required;
spread (both priming coat and finish coat) 110...150g/m²

for all kinds of interior coatings, but also for exterior coatings

12.3. Examples of Wood Coating Systems

Coating systems

Number of coats

Examples of application

exterior coating

linseed oil-priming oil

1

for doors, windows, bungalows, sheahting,

oil priming paint for outside

1...2

fences, window boxes

oil varnish for outside

linseed oil-priming oil

1

shutters, bungalows, espaliers, windows and doors

alkyd priming coat

1...2

alkyd varnish outside

1

PVA latex priming coat

1

huts, fences

PVA latex finish coat

2

goods wagons

PUR impregnating primer

1

windows and

PVA latex paint

1

other structural

PUR varnish for outside

1

elements

PUR adhesive filler

1

coating of plastic parts

SH mat varnish

1

and foamed plastic parts

interior coatings

linseed oil-priming oil

1

coloured varnishing of doors,

oil priming paint for indoors

1...2

banisters, small and kitchen

oil varnished for indoors

1

furniture (inside)

PVA latex priming coat

1...2

sheathings, floors,

PVA latex finish coat

1

kitchen furniture (inside)

linseed-oil-priming-oil

1

glossy outside coating

PVA latex priming coat

1...2

of kitchen furniture

alkyd priming coat

1

alkyd varnish

1

NC dipping varnished, colourless or NC quick sanding primer

1...2

frame furniture

SH finishing varnish, colourless

1...2

PUR impregnating primer

1

doors, banisters

PUR adhesive filler

1

and similar

PUR varnish for indoors

1

Name	Composition	Mode of application
solvents	physically acting organic compounds (e.g. acetone)	Apply by means of a sponge or similar, then rub with a clean roll of cloth, wash with warm water.
saponification agent	chemically acting alkaline compounds (e.g. ammonia water)	Apply several times with a sponge, let it rest for 10 - 15 minutes, treat with a brush, neutralize with 10 % acetic acid, then wash with warm water.

Name	Mode of application	Use
bleach liquor	Apply solution of 40 g of soda, 50 g of chloride of lime and 30 g of potash in 11 water by means of a brush; after treatment with 5 % warm sodium thiosulphate solution	for bleaching basic consumer goods and especially fir wood; good ventilation of the working rooms necessary.
acetic acid	Apply 5...10 % solution in warm state and wash and brush out thoroughly.	for especially sensitive wood species
potash lye and hydrogen peroxide	Precoat with aqueous potash solution, then apply hydrogen peroxide, finally apply acid neutralizing agent.	suitable for all wood species, removes blue stains, mould stains
sodium hydrogen sulphite	Apply warm 3...5 % solution and then wash thoroughly.	especially suitable for walnut wood
oxalic acid and salt of sorrel	Apply warm 2.5...5 % solution, let it harden and then wash thoroughly.	especially for tanniferous wood; also removal of rust and ink stains - bleaching agent is toxic,
hydrogen peroxide	Apply 30...35 % solution in sufficient quantity.	mainly for low-tanniferous wood species and for coniferous wood species
hydrogen peroxide and ammonia water	Apply hydrogen peroixide solution with 10 % ammonia water by means of a brush.	for quick bleaching of small surfaces
citric acid	Apply 3...5 % solution in a hot state, then wash and brush out well.	for brightening tanniferous wood and for removing stains caused by iron-tanning agent reactions and blue stains

Technique	Properties	Use
plain staining	solutions of heavy metal salts with dyestuffs	only for tanniferous wood species
double staining	Preliminary stains contain tan-like compounds, stains for the second coating contain various metal salts	for low-tanniferous wood; apply the second coating of stain only after the preliminary stain has dried; stains are water-insoluble and resistant to light
wax staining	solutions of metal salts, dyestuffs and wax additives ready for use	for all wood species, not in furniture construction, mat finish effect due to wax portion

Name	Components	Properties
oil varnishes	drying oils and resins; an oil-to-resin ratio of 1:1 to 1:3 yields short-oil varnishes, a ratio of 3:1 to 5:1 yields long-oil varnishes	good adherence of the varnish coating, resistant to climatic influences and moisture as well as chemicals, low hardness of the varnish coating, but high elasticity, slow drying; dyestuffs can be added
cellulose nitrate lacquers (NC lacquers)	collodion cotton, solvents such as toluene, ethyl acetate, butyl acetate and other organic compounds as well as fillers and softeners	combinable with other coating compositions, quick-drying, various levels of gloss possible, lacquer coating is elastic; not moisture-resistant, temperature-sensitive, not resistant to solvents, to oils, acids, lyes and alcohols
alkyd varnishes	alkyd resins, oils and solvents	approximately like oil varnishes, extraordinarily elastic films, high resistance to mechanical influences and climatic influences, water-proof
acid-hardening varnishs (SH-varnishes)	synthetic resins, (urea resin, phenolic resin); solvent, filler and softener, acids as hardener	high adherence, elastic and hard varnish coating, resistant to water, alcohol, spirit and a great number of solvents, temperature-resistant and non-ageing, resistant to mechanical load
polyurethane lacquers (PUR lacquers)	polyacrylate or polyester resins as well as solvents, pigments and fillers, in addition to this isocyanate as secondary component	incompatible with oil and alkyd varnishes, good adherence, hard and abrasion-resistant coatings, resistant to water, alcohol, solvents, variations of temperature
polyester lacquers (UP lacquers)	unsaturated polyester resin (hence UP lacquers), styrene and as hardener of organic peroxides in solvents	mainly for industrial processing, wood components may cause poor adherence (e.g. with the wood species Jacaranda, Iroko, Bété), combination with other kinds of lacquer possible; resistant to water, alcohol and many other substances, resistant to mechanical load and variations of temperature, brittle, cracking under impact load
polyvinyl acetate coating (PVA coating)	polymerized vinyl acetate, softener, fillers, pigments	water-dilutable, therefore not inflammable, not dangerous to health; good opacity, air-permeable, “breathing” of the undersurface possible

Name	Properties
ethyl alcohol	colourless, boiling point 78 °C, inflammable, miscible with water and all usual organic solvents, highly toxic
ethyl acetate	colourless, inflammable, boiling point 77.1 °C, non-miscible with water
acetone	colourless, inflammable, boiling point 56.3 °C, highly volatile, miscible with water and most of the organic solvents
benzene	colourless, very inflammable, boiling point 80.1 “C, non-miscible with water, but miscible with organic solvents, vapours highly toxic
butyl acetate	colourless, inflammable, boiling point 118 °C, non-miscible with water, but miscible with organic solvents
methanol	colourless, inflammable, boiling point 64.7 °C, miscible with water, highly toxic
methylene chloride	colourless, non-miscible with water, boiling point 41.6 °C
toluene	colourless, inflammable, boiling point 110.8 °C, non-miscible with water
xylene	colourless, inflammable, boiling point 139...140 °C, little soluble in water, easily soluble in some organic solvents

Name	Mode of application	Range of application
oil varnishes	multilayer application by brushing, spraying, rolling or dipping, spread per application: linseed oil-priming oil 80...120 g/m² priming paint 120...300 g/m² coating varnish 100...250 g/m²	fats, slowly drying varnishes for exterior coatings (e.g. windows), short-oil, quicker drying varnishes for interior coatings (e.g. floors)
NC lacquers	multilayer application by brushing, spraying, rolling, casting or dipping 1st spread: lacquer-to-thinner ratio 3:1 intermediate sanding 2nd spread: ratio 1:1 3rd spread: heavily thinned, rub with polishing cloth spread - 400 g/m	for furniture and interior varnishing, for toys, arts and crafts, musical instruments
alkyd varnishes	like oil varnishes	coatings with high stability like floors as interior coating and windows and doors as exterior coating; but also as boat varnish (water and weather resistance)
acid-hardening varnishes (SH varnishes)	mixing of the components in the specified ratio in non-metallic vessels; 1 to 3 spreads by brushing, spraying, casting, rolling; spread £ 140 g/m	for interior coatings which are under stress, but also for exterior coatings; for furniture, sports equipment, windows, doors, parquet and in vehicle construction
polyurethane lacquers (PUR lacquers)	mixing of the two components in the specified ratio; spreading in 1...2 applications by brushing, spraying, casting or rolling; spread £ 250 g/m²	for interior furnishings, for sports equipment, staircases, parquet, in vehicle construction, as boat varnish and for plastic coatings
polyester lacquers (UP lacquers)	used mainly industrially; several applications according to the kind of spreading; putty, primer and lacquer are applied separately by spraying, casting or rolling; lacquer spread 80...200 g/m²	especially for living room furniture, but also for other purposes like ship interior work and as boat varnish
polyvinyl acetate coatings (PVA coatings)	thinning with water as much as necessary, several applications according to the desired effect, spreading mainly by brushing; as PVA coatings are not glossy, a finish coat with oil or alkyd varnish is applied on the PVA priming coat, if required; spread (both priming coat and finish coat) 110...150g/m²	for all kinds of interior coatings, but also for exterior coatings

Coating systems	Number of coats	Examples of application
exterior coating
linseed oil-priming oil	1	for doors, windows, bungalows, sheahting,
oil priming paint for outside	1...2	fences, window boxes
oil varnish for outside
linseed oil-priming oil	1	shutters, bungalows, espaliers, windows and doors
alkyd priming coat	1...2
alkyd varnish outside	1
PVA latex priming coat	1	huts, fences
PVA latex finish coat	2	goods wagons
PUR impregnating primer	1	windows and
PVA latex paint	1	other structural
PUR varnish for outside	1	elements
PUR adhesive filler	1	coating of plastic parts
SH mat varnish	1	and foamed plastic parts
interior coatings
linseed oil-priming oil	1	coloured varnishing of doors,
oil priming paint for indoors	1...2	banisters, small and kitchen
oil varnished for indoors	1	furniture (inside)
PVA latex priming coat	1...2	sheathings, floors,
PVA latex finish coat	1	kitchen furniture (inside)
linseed-oil-priming-oil	1	glossy outside coating
PVA latex priming coat	1...2	of kitchen furniture
alkyd priming coat	1
alkyd varnish	1
NC dipping varnished, colourless or NC quick sanding primer	1...2	frame furniture
SH finishing varnish, colourless	1...2
PUR impregnating primer	1	doors, banisters
PUR adhesive filler	1	and similar
PUR varnish for indoors	1