Wood lake is a damp colour, and can be used without grinding, being made almost exclusively for marbling. It is the best red for general purposes, and has an ap­pearance almost equal to drop lake. The most useful blue is indigo. It is not by any means a bright colour but if of the best quality it is one of the most durable. It is invaluable for producing greens and purples. Chinese blue is a necessary colour but it is not very durable. It must be well ground, and with the addition of varying proportions of white nearly every shade of blue can be produced. Vegetable black will not produce a black for marbling except in combination with double its weight of indigo; it is much used. Orange lead a very heavy colour, is but little used except for the edges of account books. White is not much required as with gall and water white spots can easily be produced; however, China clay and pipe clay are used where necessary.

For grinding colors in the dry state a marble slab and muller must be procured. Large quantities are treated in a colour mill, which is simply a pair of porphyry rollers rotating in opposite directions close together. The colour has to be passed through several times before the proper degree of fineness is reached. After being ground, the colors are mixed in a cup with water. Besides the gum or size and colors, ox-gall, ammonia, spirits of wine, and oil will be required. Get a gall bag from the butcher and cut a hole in the bottom to allow the gall to run into a bottle. Gall when new is often thick, but it will thin and improve with age. For the bottle get a well fitting cork, and cut two pieces out of the sides opposite each other; then put the cork tightly in the bottle, and, without removing the cork, when the bottle is turned up a drop at a time will come out. The ammonia and spirits of wine must be kept tight with ground glass stoppers. Some of the colors require a little bees wax to prevent them rubbing off and to aid in the burnishing afterwards. It must be added while grinding. To prepare it, chop a small piece of beeswax fine, and place it in a small tinned iron or enameled vessel on a stove until it is melted. Then pour gradually into it some spirits of turpentine, stirring all the time until it acquires the consistency of honey. Allow it to cool, when it can be added to any colour and ground with it when necessary.

The operation of marbling may now be described. With the size a little thicker than good milk, fill the trough to within ½ in. of the top, pouring it through the sieve. Take the skimmer (the flat piece of wood already mentioned) and draw it over the surface of the size; if considerable resistance is felt, the size is too thick. . Throw on a few spots of colour; if these lose their shape and appear to be attracted to the sides of the trough, the size may be considered too thin. Again, if the colors crack and are a long time spreading, the size is too thick. Put into each cup or pot of colour a few drops of gall and stir it well with a small brush, which should be provided for each cup. There must also be a cup of gall and water only, with a brush.

It will be impossible here to set out in detail the manipulation of the colours to produce all the numerous patterns of marbling, but one or two of the commonest or best known designs will be described. Brown shell is a simple pattern, being a brown marble with red, yellow, and black veins. As the brown is required to spread on the size more than the other colours, it must be thicker, and it must have more gall mixed with it and a few drops of olive oil to cause the shell to be formed. Test each colour separately on the trough, skim the surface, and allow the waste to go over into the receptacle at the end of the trough. Then with the red brush, sprinkle the entire surface until it is well covered; follow with the yellow and the black, and finish with the brown, which will spread in shell like spots lighter in the centre than at the edges, driving the other colours into veins. The shell effect will vary with the amount of gall in the brown, and the larger the shell the finer the veins. As to the quantity of oil if there is too little the colour will part and produce holes here and there.

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