The author mentions that this is only applicable to vases the mouth of which is wide enough to permit the hand to be introduced. I would here, however, add, that even when it is too small for this purpose, the restoration can be equally well effected as follows:—Make the core of wet clay, or, better, of beeswax, then paste over it thin tough paper. Cover this with gum-arabic solution, and set the pieces on it. When dry, melt out the wax or clay.
Fish-gum, colle de poisson—that is to say, what is generally called sturgeon’s bladder, which includes the bladder of several kinds of fishes dissolved—is best for glass, marble, porcelain, and all kinds of mending where the cement should not show. This, when combined with oil, is said, if mixed with cloth-dust and fibre of wool or silk or cotton, to spin up into thread.
MENDING GLASS
WITH SEVERAL ALLIED PROCESSES
APPROVED CEMENTS—SILICATE OF SODA
“Glück und Glas
Wie bald bricht dass.”
“Good luck, like glass,
Soon breaks, alas!
Yet skill can bring it so to pass
As to mend a fortune or a glass.”
—Old German Proverb.
Putty is naturally the first cement which suggests itself in connection with the mending of glass, since this latter material is most familiar to the world in the form of windows, although in many places—as, for instance, Florence, where it is called mastico and pasta—it is little used or known. The word is from the French potée, which also means a potful. It is very useful, not only for setting glass-panes, but for filling holes in wood, and forms a part of certain mixtures as a cement for moulding ornaments. It may be weak and brittle, or else strong and very hard, according to the manner in which it is prepared. It is commonly made by combining chalk in paste, with water, with linseed-oil; other powders are also used. In America it is made with pulverised soap-stone and oil. Its excellence depends on the quality of the oil and the care with which it is kneaded. It should be kept in a damp cellar, in wet cloth or under water. Should it dry and become brittle, fresh oil must be added.
“To take hard old putty from glass window-panes, cover it with a mixture of one part of calcined lime, two of soda, and two of water” (Lehner). Oxide of lead combined with oil makes an excellent but yellow putty. It sets very hard.
The white or grey oxide of zinc combined with linseed-oil or linseed-oil varnish makes a cement which is used for making glass adhere to wood or metal.
Thick lacquers, such as copal or amber, may be used instead of common varnish with better effect, and the composition is better when calcined lime or oxide of lead are added. The excellence of the cement depends on the degree to which the ingredients are amalgamated or rubbed in together; and this rule holds good for all similar mixtures.
Varnish, or heavy or “flat” lacquer of copal or amber, forms of itself a strong adhesive, with the only drawback that it takes a long time to dry.