WAX AND PLASTIC BURNOUT
Posted by
William Reidsema
on 2001-09-28 03:47:36 UTC
I've been casting from wax and plastic patterns
for more than 35 years. I've always used cristobalite
investments like "Kerr Satin Cast" and "Randolph and
Ransome". When casting the higher temp. waxes or
plastics, it is imperative that the investment be
mixed vigourously for at least 2 minutes (adds
strength) and that the burnout cycle allows the
invested mold to dry completely. Once it is dry, it
will not crack. Steam dewaxing should only be used on
wax patterns that will melt below 165f. The higher
temp. waxes will expand too rapidly causing a very
rough casting. Also, when casting plastics, be sure to
allow at least a quarter inch space between patterns
and the flask wall. Otherwise even dry investment can
blow through to the flask wall or another pattern.
Bill Reidsema
for more than 35 years. I've always used cristobalite
investments like "Kerr Satin Cast" and "Randolph and
Ransome". When casting the higher temp. waxes or
plastics, it is imperative that the investment be
mixed vigourously for at least 2 minutes (adds
strength) and that the burnout cycle allows the
invested mold to dry completely. Once it is dry, it
will not crack. Steam dewaxing should only be used on
wax patterns that will melt below 165f. The higher
temp. waxes will expand too rapidly causing a very
rough casting. Also, when casting plastics, be sure to
allow at least a quarter inch space between patterns
and the flask wall. Otherwise even dry investment can
blow through to the flask wall or another pattern.
Bill Reidsema