The staining being effected, a slight coat of a diluted or light tint of the upper or deeply coloured varnish may be painted over and left to dry.
If time is not an important item for consideration, a turpentine varnish may be applied.
An excellent first colouring can be effected with the transparent preparation of gamboge. This material has for long, perhaps always, been in request for coloured varnish, as it can be used with (after due preparation) either alcohol, turpentine or oil. If dissolved in the last, the drying will take so long as to be practically useless to the repairer. The turpentine solution is more rapid, but not sufficiently so for the restorer under ordinary circumstances.
It will be therefore plain that an alcoholic solution of gums or resins will have to be relied on for obtaining the best results when time is limited.
The solution of gamboge in alcohol is, when used alone, too weak or insufficient in body; it is therefore advisable to incorporate with it some other material of a resinous or gummy nature, but such as will not impair the transparency. Among the most useful are the bleached or white shellac. This, as it leaves the manufactory, is not always in a condition for immediate use by the restorer; it should be washed in water and then dried well, pounded up and placed in a bottle with about four-fifths of alcohol; after remaining in solution for some days the clear portion can be poured into another bottle and retained for use.
This, when used alone in its colourless condition, will possibly have, when dry, too much glare upon its surface, but the colouring matters put into it may oppose this sufficiently.
The use of a little gum guacum in solution will be found occasionally advantageous; this gum is fairly hard and will lower the colour and prevent too much of an approach to gaudiness, that is, if a highly coloured varnish has been found necessary. When it is desirable to dispense with lac of any kind in the varnish, other materials can be found that will perhaps answer the purpose as well, if not better; a solution of benzoin has no colour sufficient in itself and therefore may be used as a priming or mixing with the gamboge or with dragon's blood if that is desirable; the latter, like the gamboge, requires something to give it body.
Dragon's blood will soon let the operator know that its power of colouring to a staring degree will require suppression. To lessen its strength the following may be taken as an excellent means, and will reduce the violence ad libitum. With a lighted candle, wax for preference, smoke a piece of clean glass, and with a camel hair brush remove the black and stir it carefully with the coloured varnish. Care must be taken that too large a quantity is not put in, or an unpleasant tone, even blackness, will be the result.
With regard to the strength of the red, the same precautions must be taken: on comparing the varnish of a very red old master of Italy, say a Landolphi, with some made with a fairly strong solution of resin and dragon's blood, the violence of colour in the latter will be very apparent. At a little distance off the old master will look very modest while the other will seem coarse and vulgar.
For softening purposes a very small quantity of gum thrus may be used, too much will result in tackiness.