PolyFoamTM R-8 is well known for
casting picture frames and other decorative items. It is also very useful
in a more utilitarian application: as a mother-mold material. PolyFoamTM
R-8 is fast curing, lightweight, durable, and economical. The procedure
for making a PolyFoamTM R-8 mother mold is fast, simple, and equally effective
over brush-on, spray-on, or clay blanket for poured blanket molds.
Start with a model mounted securely on a baseboard. The size of the baseboard
will determine the size of the mother mold. Construct your brushed or
sprayed rubber mold or clay blanket as you normally would. Treat the outside
of the fully cured rubber mold with Pol-Ease® 2300.
Assemble a reinforced mold box around the baseboard and spray with Pol-Ease®
2300. You may want to add a wood frame that fits snugly inside the mold
box, to provide added strength to the foam edges. The PolyFoamTM R-8 will
bond to this frame. Construct a sturdy, rigid top for the mold box, and
spray with Pol-Ease® 2300. The top should be well vented to relieve
excess pressure built up by the rising foam. You must be able to attach
the top to the mold box quickly and securely. The top will form a flat
surface on the rising mass of foam.
Estimate the volume in cubic feet of the mold box less the volume of the
rubber- or clay-coated model. Multiply the volume, in cubic feet, by the
desired density of the foam to determine the amount of foam required.
For most mother mold applications, 9 pounds per cubic foot works well.
Weigh the appropriate amounts of PolyFoamTM R-8 Part A and Part B into
separate containers. Pour and scrape the contents of each container into
a third container for mixing. Mix for 20 to 30 seconds with a Turbo Mixer
mounted in an electric drill. Pour the mixed contents into the mold box.
Close the top of the box quickly. Use strong clamps or straps to secure
the top against the pressure exerted by the expanding foam. After 15 minutes,
disassemble the box and remove the mother mold.
The finished mold shell is lightweight, tough, and relatively low cost.
It will outlast most other mother mold materials in a rough handling situation
like a concrete-casting shop. |
