An amount of10 g tannicacid is dissolved in 1 litre warm water.The stain is applied cold. It is usual practice to then apply a second layer consisting of a solution of 10 g potash (K2CO3) in a litre of water.The colour is lightgrey-green.
RECIPE 2: LYE STAIN
An amount of 5 g of tannic acid is dissolved in 1 dl lukewarm water; 50 g potash is dissolved in 5 dl hot, almost boiling water, and 4 dl cold water and 1.25 dl lye solution (12 % lye in water) areadded.Thetannic acid solution is mixed with the potash solution. This must be prepared in a ceramic vessel. It gives a stronger grey-green tone than the first recipe. The final colour emerges after eight to 14 days. The stain should stand a few days before use. Lye stains are highly alkaline, and protective clothing must be used.
RECIPE 3: IRON VITRIOL (GREEN VITRIOL)
Iron vitriol is based on ferrous sulphate (iron(II)sulphate). In liquid form it can irritate skin. A good impregnation solution consists of 10-13 g per litre of water, with a little alum added as afix, and givesthetimberan even and shiny silver surface. Green vitriol also has a slight impregnating effect as well as being a flame retardant.
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