(a) This operation is performed in the same manner whether the work has been oil grained or spirit grained. In overgraining, watercolours are used; and, in order to make them adhere to the underlying graining, whether in spirit or in oil, it is necessary to prepare the work to receive them, otherwise they would run off the surface at once. One method is to rub dry powdered whiting. quickly over the surface with a soft rag, removing superfluous powder afterwards, and the grainer can at once finish the work. Another plan, which is principally used when a large piece of work is in hand, is to rub a mixture of fullers' earth and water over the graining, and wait until it is perfectly dry before commencing to overgrain. Grind Vandyke brown, or burnt umber, in water, and thin with equal proportions of water and beer, The colour should be a trifle darker than the undergraining; a little practice will teach the tints that are best suited to the various woods to be imitated.
The colour is applied by a wide hog brash, drawn over the work, generally in the direction of the veins formed by the combing. There are several descriptions of orergraining brushes in use; those most generally employed are thin and flat, with occasional intervals between the tufts of hair. The knots and figures must be lightly touched up with the overgrainer, and the whole gone over quickly with a badger softening brush. The overgraining dries quickly, and the varnish may be then applied, although it is well to wait some hours, so as not to run any risk of removing the graining colour. Sometimes a tolerably strong solution of soda with a little burnt sienna is used for the figures, applying the mixture where these are required, and then washing over the work with a sponge and water. Where-ever the soda has been applied, the graining colour will be removed. Go over the whole with a wash made of equal parts of beer and water, and then overgrain, as above described. As a general rule, avoid harsh contrasts between the graining colour and the ground.
(6) In the mixing of oil graining colour, it is necessary that the colour should work clean and free. Sometimes the colour will work stiff and dirty, and in this state will not only produce dirty work, but will occupy thrice the time in rubbing in, compared with colour properly mixed. Oil graining colour also requires to be megilped - that is, oil colour alone will not stand when it is combed; the marks made with the comb will all run one into the other, and will thus be obliterated. To prevent this running, the colour requires to be megilped, so that the comb marks will retain the exact form left by the comb. This is accomplished by the use of beeswax, soft soap, hard soap, lime water, whiting, and pure water. When beeswax is used, the best means of dissolving it is to cut the wax into thin shavings or shreds; these are put into a suitable can half filled with pure linseed oil, into which a red-hot poker is plunged, and stirred well, This will dissolve the wax thoroughly and mix it with the oil. When the wax is all dissolved, the vessel should be filled with either oil or turpentine, which further dilutes and mixes the wax, and serves also to prevent it from congealing, so that it may mix with the graining colour thoroughly.
This should be seen to, or else the wax is apt to remain in lumps; and when the colour is spread upon the work, for graining, the wax will be spread unequally, and will not dry in parts, so that it is absolutely necessary that the wax should be thoroughly mixed with the graining colour to produce good work. If soft soap is used, it should first be thoroughly worked up on a palette or a board with either whiting or patent driers; this breaks up the soap, and amalgamates it with the driers, and it will then mix properly with the graining colour. Another method is to break up the soft soap in water to a thick froth or lather; in this state it may be beaten up with water and thoroughly mixed with the oil colour. When the lime water is used, about 2 lb. of slaked lime should be thoroughly mixed in a pint can full of water, and the lime allowed to settle; a portion of the water may then be added to the graining colour, and the two well stirred together until they are thoroughly amalgamated. If whiting is used, it should be ground in oil, and then mixed with the graining colour. Pure water will also answer the purpose. The wax is the most effectual, but there are some objections to its use.
On the whole, pure water is preferable, for if it is well mixed with the oil colour, it megilps it sufficiently to hold the combing until it sets; the water then evaporates and leaves no injurious effects behind, and the projection of the grain is less than it is if any other medium is used.
The most useful colours for mixing oak-graining colour are raw and burnt Turkey umber, Oxford ochre, Vandyke brown, and burnt sienna. The first three, with the addition of ivory black, are all that is required for mixing any shade of graining colour. For light oak or wainscot graining colour, mix 2/3 rds linseed oil with 1/3rd turpentine; add a little Oxford ochre and raw Turkey umber in sufficient quantity, according to the shade required and amount of stuff mixed. Terebine or liquid driers should be added, the quantities being regulated according to whether the graining colour is required to be quick or slow drying. A safe quantity to use, if the liquid drier is of the best quality, is about 1/2 oz. to a pint of colour. This will cause the colour to dry in about 7 or 8 hours, but twice the quantity may be used with safety if the colour is required to dry very quickly. Sugar of lead ground in oil may be used as a drier for graining colours, but the liquid drier is better. After adding the liquid driers, beat or stir well up together; add pune rain water in the proportion of 1/2 pint of water to 3 pints of oil and turps; beat or stir up until the whole is thoroughly mixed together, after which strain through a fine strainer or a double fold of fine muslin.
The colour should be thinned until it works freely and lies on well, so that when the colour is being brushed over the work to be grained, it will lie on evenly, and be easily spread, and will look clean and of one uniform shade of colour. Care and cleanliness of working are necessary to the successful carrying out of this work; and it is essential that the colour, the brushes, and all working tools should be clean to begin with, and be kept clean.