A very neat way to mend a piece of cracked glassware with sodium silicate or water-glass came to the writer's notice some weeks ago. A cut glass decanter which the owner valued very highly had a had crack running irregularly around the bottom and partly up the side. In addition to preventing its use, it rendered it unsightly.
To remove all appearance of the crack, the decanter was warmed slowly and then sealed with its own ground stopper. The water-glass was then applied with a broad brush on the outside of the crack, and as the air cooled inside the external pressure forced it into the crack, which completely disappeared and was rendered perfectly water tight to cold water at least.
Fig. 298 - Mending a cracked bottle.
Since seeing the above the writer has tried the same operation with success on a wide-mouthed jar, but obtained a much better vacuum and therefore better results without heating the jar.
A deep basin was procured, and in the center a candle was arranged, as shown in Fig. 298. The basin was then filled with water and the cracked jar inverted over the lighted candle: as the air in the jar was consumed by the candle, it was slowly lowered into the water which effectively sealed it. The water-glass was then applied as in the previous operation and the whole left to harden. The water-glass took six to eight hours to set and then the outside of the bottle or jar was washed with a cloth dipped in hot water to remove all superfluous water glass, as an extra precaution, the longitudinal seam of each was re-soldered so as to close any leak that may have been sprung during the process of removing the top and bottom of the can. To increase the strength of the leader the cans were so arranged that the longitudinal seams of the successive sections were staggered as shown in the illustration so as to form a symmetrical and regular spiral running around the leader. Each can as it was soldered to the leader was painted on the inside wall with a thick coat of paint, special attention being given to the joints. After the leader was completed the outside also was protected with several coats of paint.