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PORCELAIN INLAYS 171

furnace, if satisfactory results are to be obtained.
A neglect of these precautions will be likely to cause
the inlay to crack alongside the core.
Whenever an inlay is subjected to the force
or pressure of mastication a certain thickness
of the porcelain is needed, and just in propor-
tion to the shallowness of the cavity, so is an
undercutting or grooving, and consequent weakening

of the porcelain, demanded in many cases. The
matrix may be made of gold or platinum, although
gold is only applicable to a low-fusing porcelain.
Gold can be more easily adapted to the cavity than
platinum, and one of the advantages of the Jenkins'
porcelain is that it can be fused in a gold matrix.
Platinum can be successfully used, but its accurate
adaptation demands a great amount of skill, time,
and patience. It must be frequently removed from
the cavity and annealed during its adaptation, and
tine margins are only secured by much patient
burnishing. The platinum is gradually adapted,
" little by little," so to speak, removing and anneal-
ing almost continually. The platinum that gives
the best results is two of an inch thick, and as
soft as platinum can be made. The extreme of soft-
ness can be obtained by covering up the platinum
with unslaked lime, and thoroughly heating it in a
furnace or with a blow-pipe.