Dyeing Timber – Harewood by Richard Higgins
It would seem that to buy new harewood or other dyed timbers today is all but impossible and supplies of old coloured veneers similarly unattainable. There are available (from Crispins etc.) Italian imports as used in their modern marquetry reproduction furniture but these are incredibly thin knife cut veneers with such vivid dyes that for restoration purposes they are all but useless. Frequently replacements are needed for losses to inlay work, particularly on the often quite wonderful decoration so often found on the finest furniture of the Geo. III period. The use of uncoloured sycamore, maple, lemonwood etc., with only its surface coloured after it has been laid, is never really convincing especially after a few years of UV light exposure. There is also the problem of preventing stains bleeding into adjoining pieces such that the design looses its sharpness and precision. Better then to have a method of producing veneers of the thickness required for restoration of period surfaces which is of even colour throughout its entire thickness.
Holly is by far the easiest timber to colour throughout the thickness of a veneer; pear works well particularly for black and similarly was often used, sycamore unfortunately never seems so successful but is worth persevering with if you are having to match an original piece. The greener the timber the better, certainly never use kiln dried material. North Heigham sawmills generally have green holly and will sell it in small quantities. Buy a stock once a year and keep it in a damp place with little air circulation. Moulds will grow on the surface but it will not season effectively and certainly won’t start to rot in that time. The thinner the veneer the quicker the process although I would suggest that somewhere around 1.2 to 1.5 mm is most appropriate. Give yourself plenty of time before you wish to start working on the piece; two to three weeks should give you time to prepare exactly the colours you require although you might consider it worth making a stock of basic colours which you alter as needed. The problem with this is preventing the veneers from drying out as once they have lost there natural moisture content it is very difficult to get the dye to penetrate completely. This problem can sometimes be obviated if the veneer is prepared to near precise thickness before adjusting the colour so that final scraping of the inlayed piece removes very little of the dyed veneer.
Generally a copper vessel is best for preparing the veneers. Much copperware is available from down market antique centres and craft type gift shops as they are imported in large quantities from the far east. They are relatively inexpensive, are often beautifully made and will last a lifetime. They look good hung in any workshop! Whatever colour you require first soak the veneers in clean water for four or five days. This acts as a purgative and much slime and scum will be drawn out and float to the surface. Clean this off and change the water twice during this time. Let them dry naturally for about twelve hours before dying commences. This seems to enable the dyes to strike more rapidly. Once dyed they should be left to cool in the liquid dye and slowly dried in the air, never with the help of heat as this would appear to bring the dye to the surface leaving the surface colour more intense and the centre faded colour.
The following are adapted traditional recipes for obtaining different coloured veneers which should all be possible to reproduce in the workshop.
Cover the bottom of the pan with chip logwood, add the veneers and let it simmer for three hours. The add a few ounces of powdered verdigris (copper acetate), a few ounces of copperas (iron sulphate) and an ounce of crushed nut galls (the knurled growths from oak trees). Simmer this for a couple of hours each day and let it cool. Continue until the depth of grey or black required is achieved.
This does not require heating but should be carried out in a ceramic vessel (an old kitchen casserole dish with lid is ideal). Take a quart bottle and half fill it with a pint of saturated iron sulphate solution. To this add four ounces of finely crushed indigo. The bottle should be in a sink at this point since the mixture will effervesce and may spill over. Keep this mixture as a stock solution; indeed it should be left for a couple of weeks for the strongest colour to develop. To your dyeing vessel put sufficient water to cover the veneers to be stained and add the dye to the water to achieve the required density of colour testing by dipping a plain sheet of paper into the solution. Striking is even more successful if you boil your already soaked veneers and then let them partially dry for a few hours previous to immersing them into the dye.
Into a gallon of water add half a dozen small lumps of quick lime, stirring it well; let it settle and strain off the clear liquid. To the clear liquid add ten ounces of best turnsole, and simmer the already prepared veneers until the colour is penetrated. Do not boil the liquid as this tends to weaken the colour.
A pound of Barberry root is converted to dust and put into the copper vessel. Add 1 oz of turmeric and a gallon of water. Boil the prepared veneers in the liquid for three hours turning them regularly. When cool add ½ a fluid ounce of aqua fortis (nitric acid) to fix the colour. Leave them in the cool liquid overnight and then remove and rinse before drying slowly.
A Much Brighter Yellow
To a gallon of water add one pound of French Berries and boil for a couple of hours until the colour has penetrated. The colour is then brightened by adding the following brightening mixture to the existing liquid.
To a pint of 30% nitric acid add one ounce of grain tin and a walnut sized piece of sal-ammoniac (ammonium chloride) and after shaking periodically for three days until dissolved the solution is ready for use. Pour a few ounces into the existing liquid. Stir and leave the veneers in for a few hours or until the necessary brightness has developed. This mixture can be added to any of the recipes given and will help to both brighten and fix the colours with more permanence.
Start the process as with either of the yellow recipes, but instead of adding the nitric acid mixture use the vitrilated indigo as used in the fine blue recipe above until the right shade of green is achieved.
Dissolve four ounces of verdigris (copper acetate), ½ ounce of sap green (Juice of the buck thorn berry) and ½ ounce of indigo in three pints of clear vinegar. Boil the veneers for about three hours until the colour has penetrated. The hue can be altered by varying the proportion of the ingredients.
To a gallon of water add ½ lb of genuine Brazil dust and boil the veneers in it for three hours. Then add ½ ounces of alum and ½ ounces of aqua fortis. Keep the solution warm, only, until the colour has struck through.
Add ½ pound of logwood chips to a gallon of water. Put the veneers in and boil for three hours. Then add enough of the brightening acid until the colour appears. Keep the solution at about 60 degrees C. until the colour has penetrated. The logwood must be fresh and the other rubbish generally found with it removed. Fresh logwood is bright red but turns brown with age.
Boil the veneers in a gallon of water with ½ pound of logwood chips for at least three hours. Then add 1 – 2 ounces of pearl-ash (potassium carbonate) and ½ ounce of alum. Boil this for two to three hours every day, till the colour has struck right through. If you require a redder hue to the purple then add Brazil dust to the original solution. This colours the wood red as with the logwood but the pearl ash does not react with it turning it purple.
Boil the veneers in 1 gallon of water with ½ pound of logwood chips or powder. When the colour is well struck add some of the vitrilated indigo solution till the purple is of the shade required.
This can be achieved by first dyeing yellow and then transferring the veneers to the bright red dye.
In an old cast iron pot boil up in a gallon of water and half a gallon of vinegar a pile of very rusty nails and other old iron. In the copper vessel pour this liquid over ½ pound of logwood chips and 1 oz of bruised nut galls. Boil the veneers for two hours a day, topping up with more rusty water until the colour has struck through.
Keep a tin full of old iron and from time to time sprinkle the contents with Spirits of Salt (Hydrochloric Acid) until they are very corroded. On top of about six pounds of corroded iron pour 1 gallon of water in which has been dissolved two ounces of salt of tartar. Pour off the liquid into the copper vessel and add the veneers. Boil for three hours and then add four ounces of green copperas (Iron Sulphate) and keep the whole warm until the dye has penetrated.
Dyeing Timber – Harewood by Richard Higgins