Page 19 - My FlipBook

In a series of experiments carried on for the
purpose of studying some of the phenomena of the
Phenomena met in
fusing of the various porcelains, cubes of porcelain
Tusins Porcelain.
5 mm. on each face, weighing approximately 2.5
grains when thoroughly dried, were taken for a standard (Fig. i). The
first experiments were to determine the fusibility of the different porce-
lains. As porcelains are indefinite compounds, they have no definite
fusing point. Porcelains which ordinarily vitrify from 2.080 to 2,500
degrees can be fused on pure gold by allowing long enough time. The
experiments showed that Brewster's enamel body can be properly fused
on pure gold in from fifteen to forty-five minutes. The difference in
time depends upon the heat applied. Close's body (Justi's) requires

Fig. I.

from thirty minutes to one hour and fifteen minutes to fuse properly
on pure gold. Brewster's foundation body, S. S. White's inlay and
Whiteley's inlay porcelains require from one to three hours to fuse on
pure gold. The Consolidated Company's high fusing porcelain requires
from eight to ten hours to fuse on the same material.
It was found that Brewster's foundation body. Close's body (Justi's),
S. S. White's and Whiteley's inlay porcelains could be fused on 10 per
cent, platinous gold, which fuses approximately at 2,115 degrees, in from
fifteen to thirty minutes. Tests were also made with these porcelains on
15 per cent, platinous gold, which fuses approximately at 2,175 degrees.
It then required from ten to twenty minutes to fuse Brewster's foundation
body, S. S. White's and Whiteley's inlay porcelains.
In studying fused porcelain under the microscope, it was observed
that those porcelains which were fused at a lower temperature for a long
time, presented more homogeneous and more highly glazed surfaces,
while the surfaces of porcelains which were fused at a high temperature
for a short time appeared more granular. The cubes were then frac-
tured and the inner portion examined under the microscope. It was
invariably found that those porcelains which were fused for a long time
at a lower temperature were more homogeneous in te.xture.

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