In order to cover the articles, which may be flat or round, with this coating, they must first be polished quite smooth and clean; then they are coated with thin, hot, white glue. When the coat is thoroughly dry, the glue is rubbed off again with fine glass paper. The mass is prepared as follows: Take 3 pounds (more or less, according to the number of articles) of the purest and best collodion; grind upon a clean grinding stone twice the quantity that can be taken up with the point of a knife of Krems white, with enough good pale linseed oil as is necessary to grind the white smooth and fine. Take a clean bottle, into which one-half of the collodion is poured; to this add the ground white, which can be removed clean from the stone by means of a good spatula and put in the bottle. Add about 100 drops of linseed oil, and shake the mass till it looks like milk.

Now painting with this milky substance may be commenced, using a fine hair pencil of excellent quality. The pencil is not dipped in the large bottle; but a glass is kept at hand with an opening of about 1 inch, so as to be able to immerse the pencil quickly. The substance is not flowing like the alcohol lacquers, for which reason it may be put on thick, for the ether, chiefly constituting the mass, evaporates at once and leaves but a very thin film which becomes noticeable only after about 10 such applications have been made. Shake the bottle well each time before filling the small glass, as the heavy Krems white is very apt to sink to the bottom of the bottle. If it is observed that the substance becomes too thick, which may easily occur on account of the evaporation, a part of the remaining ether is added, to which in turn 30 to 40 drops of oil are added, shaking it till the oil appears to be completely dissolved.

The operator must put on the mass in quick succession and rather thick. After about 10 coats have been applied the work is allowed to rest several hours; then 3 or 4 coats of pure collodion, to which likewise several drops of oil have been added, are given. Another pause of several hours having been allowed to intervene, application of the mass is once more begun.

When it is noticed that a layer of the thickness of paper has formed, the articles, after drying thoroughly, should be softly rubbed off with very fine glass paper, after which they require to be wiped off well with a clean linen rag, so that no dust remains. Then coating is continued till the work seems serviceable.

A few applications of pure collodion should be made, and when this has become perfectly hard, after a few hours, it can be rubbed down with a rag, tripoli, and oil, and polished by hand, like horn or ivory. This work can be done only in a room which is entirely free from dust. The greatest cleanliness must be observed.