Don Stephan
Posts: 825
Joined: 2003-07-18
Location: Cincinnati, Ohio
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Thought the following excerpt from "The Complete Manual of Wood Veneering" by William Lincoln describing commercial dying of veneers might be interesting. It appears on pages 71-72 of the 1995 reprint of the 1984 edition.
(No opinion is being expressed, the following is offered solely because it is germane to the discussion and for anyone who might be interested.)
"... In practice, the veneer craftsman who intends to tacke making his own harewood or dyed woods, should equip himself with a pH meter, in order to control the three variables (a) the veneer, (b) the water supply and (c) the dyebath solution."
...
"This is how dyed veneers are produced commercially.
"a. Selected veneers are placed in an autoclave under vacuum pressure to remove the air, and free cell water from the veneers, and also much of the resins, tyloses, tannin, etc., which would hinder complete penetration.
"b. The pH readings are taken and the three components scientifically adjusted for neutralised and de-mineralised water; the veneer and the dyebath acidity/alkalinity adjustments made.
"c. When the vacuum process is complete, valves are opened to permit the dyestuffs to fill the autoclave, and obtain partial penetration.
"d. A re-circulating process begins in which the dye is fed from the (sometimes heated) reservoir tank, through the autoclave to assist penetration.
"e. The pressure pump now applies up to 120 psi, (351.19 Kg/cm2) for maximum prenetration, and this is maintained for a calculated length of time.
"f. The autoclave is emptied and the veneers rinsed thoroughly.
"g. They are then given a Fixanol PN (ICI) treatment for one hour at 50 degrees C to fix the surface colour. The colour tends to migrate to the surface and be a darker shade than the centre of the veneer. However, when laid, sanded and polished the shade of colour is restored and this is taken into account.
"From the above description, the home veneer craftsman can see that attempts to satisfactorily dye veneers in a tin bath are not likely to obtain the desired results!"
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