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44 MECHANICAL DENTISTRY AND METALLURGY.
After the crude substance has been passed through a
triturating machine it is thoroughly washed and dried to
remove any foreign substances ; it is then meked and sulphur
and the coloring' matter added. It is due to the presence
of the sulphur that the rubber hardens when brought in
contact with heat (vulcanization). The more sulphur
added, the harder the product. Manufacturers as a rule
do not make their formuke known, but the following,
selected from those of the late Professor Wildman, are
thoroughly reliable:
RUBBER COMPOUNDS.
Red. Black.
Caoutchouc, 48 parts. Caoutchouc 48 parts.
Sulphur, 24 " Sulphur, 24 "
Vermilion, 36 " Ivory Black, 24 "
Pink. White (Grayish).
Caoutchouc 48 parts. Caoutchouc, 48 parts.
Sulphur, 24 " Sulphur, 24 "
White Oxid of Zinc,.... 30 " White O.xid of Zinc,.... 96 "
Vermilion, 10 "
Flasking.—After removing the cast and denture from
the articulator, they should be placed for a few minutes
in cold water, so that the plaster will become saturated,
and thus prevent its absorption of the water from the newly
mixed plaster in flasking, which would in a measure pre-
vent the proper adjustment of the cast.
When the plaster has been thoroughly mixed (to a
creamy consistency) fill the lower part of the flask about
half full and introduce the model, slightly inclined at first,
then press it down to a horizontal position, well imbedded
gradually grows darker upon exposure. It takes its common name,
rubber, from the fact that it was used many years simply as an eraser
of lead pencil marks. It is insoluble in water or alcohol, and is remark-
able for its elasticity. Caoutchouc melts at 248° F., and remains in an
unchangeable fluid state up to 500° F.
44 MECHANICAL DENTISTRY AND METALLURGY.
After the crude substance has been passed through a
triturating machine it is thoroughly washed and dried to
remove any foreign substances ; it is then meked and sulphur
and the coloring' matter added. It is due to the presence
of the sulphur that the rubber hardens when brought in
contact with heat (vulcanization). The more sulphur
added, the harder the product. Manufacturers as a rule
do not make their formuke known, but the following,
selected from those of the late Professor Wildman, are
thoroughly reliable:
RUBBER COMPOUNDS.
Red. Black.
Caoutchouc, 48 parts. Caoutchouc 48 parts.
Sulphur, 24 " Sulphur, 24 "
Vermilion, 36 " Ivory Black, 24 "
Pink. White (Grayish).
Caoutchouc 48 parts. Caoutchouc, 48 parts.
Sulphur, 24 " Sulphur, 24 "
White Oxid of Zinc,.... 30 " White O.xid of Zinc,.... 96 "
Vermilion, 10 "
Flasking.—After removing the cast and denture from
the articulator, they should be placed for a few minutes
in cold water, so that the plaster will become saturated,
and thus prevent its absorption of the water from the newly
mixed plaster in flasking, which would in a measure pre-
vent the proper adjustment of the cast.
When the plaster has been thoroughly mixed (to a
creamy consistency) fill the lower part of the flask about
half full and introduce the model, slightly inclined at first,
then press it down to a horizontal position, well imbedded
gradually grows darker upon exposure. It takes its common name,
rubber, from the fact that it was used many years simply as an eraser
of lead pencil marks. It is insoluble in water or alcohol, and is remark-
able for its elasticity. Caoutchouc melts at 248° F., and remains in an
unchangeable fluid state up to 500° F.
