1. Dissolve one ounce of borax in a half pint of water, and add slaked lime to form a thin paste. Brush this over the retort, and let it dry gradually. Then apply a coating of slaked lime and linseed-oil beaten together. Let it dry a day or two before use, and fill up any cracks which may appear with lime au<3 linseed-oil.
2. A lute which is said to be very efficient is made as follows: Take fragments of porcelain, pulverize and sift them well, and add an equal quantity of fine clay, previously softened with as much of a saturated solution of muriate of soda as is requisite to give the whole a pioper consistence. Apply a thin and uniform coat of this composition to the glass vessels, and allow it to dry slowly before they are put on the fire.
Good fire-clay is mixed with a little sand to prevent it splitting off. A little cut tow, or horse-dung, or asbestos, is usually added to increase its coherence. It should be beaten to a stiff paste, and rolled out before application. The glass should be first rubbed over with a little of the lute mixed with water, then placed in the center of the paste, rolled out to about a quarter or third of an inch in thickness, and the edges of the latter raised and molded to the glass, taking care to press out all the air.
Mix equal parts of brick-dust and litharge, and beat them into a paste with linseed-oil. Apply this with a stiff brush, and dust it over with coarse sand. Dry it in a warm place.
Notwithstanding Mohr's high reputation we have not much confidence in this lute if exposed to heat. It is no doubt serviceable at common temperatures.
Fire-clay, 15 lbs.; carbonate of soda, 1 lb.; water sufficient to make a thick paste. Apply to the crack when at a good working heat, and cover with fine coal-dust.
Five parts fire-clay, 2 parts white sand, 1 part of borax pressed and ground. Mix the whole together with as much water as may be necessary to bring it to the consistence of putty. Roll it in the hands to a proper length and apply it over the crack, pressing it with a long spatula into the crack.