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, {501} 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.