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An introduction to resin casting - by Kurt Hofmeyer

My method of making two-piece molds for hollow castings.

NOTE: I make molds and castings only for my own and not for commercial purposes. Therefore the following should be only hints for those who want to do the same. My method works well with fluid mold materials becoming solid after several hours and fluid resin.


Click the thumbnails !

MOLD_001.JPG (11532 bytes) The master.
MOLD_002.JPG (15230 bytes)

The master is stuffed by plasticine with a conical pedestal. The windows are closed from inside with thin plastic sheet.

MOLD_003.JPG (7369 bytes) The prepared master is put into a dismantable plywood box, held together by tape. 
MOLD_005.JPG (20798 bytes) My vacuum pump. After stirring the two components of the RTV-mold-material (RTV = Room Temperature Vulcanizing) there are many airbubbles in the RTV that I use. They don't ascend all during the setting time of the RTV (about 24 hrs.) and produce defective spots in the mold. To remove these bubbles I use the vacuum pump. After 5 minutes of pumping the surface of the RTV looks like cooking water. Maybe other RTV has not such problems.
MOLD_006.JPG (11808 bytes) Filling the box with RTV.
MOLD_008.JPG (8580 bytes) The outer part of the mold is almost ready. 
MOLD_009.JPG (6180 bytes) The cuts are for a good fit of outer and inner part during casting.
MOLD_010.JPG (8247 bytes) The outer part must be sprayed with a release agent oder greased with wax that the two mold-parts can be separated later. The master is put into the mold again.
MOLD_011.JPG (15686 bytes) Thin plastic-rods are glued to high points of the master to prevent air from making bubbles into the casting. 
MOLD_012.JPG (8819 bytes) The mold is completed.
MOLD_013.JPG (6946 bytes) The outer and the inner part of the mold.
MOLD_014.JPG (6158 bytes) The outer part is filled with resin (about double weight as the later casting). The resin must be filled in all cavities; use a spatula or a finger (with glove). Then the inner part is put in and the surplus resin will flow over. (My resin is very thin flowing and begins to get solid after about 4-5 min.) The shown casting is the result.

Two samples of Dodge Crewcab Pickups.

Text & pictures are 2002 - 2004 Kurt Hofmeyer

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