A
Real Moldmaking Challenge
From the earliest conversations with Steve, it
became clear that several unconventional techniques would be required
to successfully complete the task at hand. To appreciate the unique aspects
of the project, consider the following. The giant termite mounds were
located in remote areas of Ghana. No electrical power was available, and
the temperatures during the the day could exceed 100°F (in the shade!).
The termite mounds ranged from 6 inches to over 15 feet in height, each
with enormously different detail, texture, and form. In addition, these
towering structures are created from a rather unusual medium over which
to apply liquid mold rubber—termite saliva and Ghanian dirt!
Each mound was its own moldmaking challenge.
Polygel® Spray 50 and Poly Plastic Shell Meet the Challenge
Our discussions quickly focused on the technique
of spraying liquid mold rubber. Pouring was strictly out of the question
and brushing would have been impossible, both economically and practically.
Polytek®'s patented Polygel® Spray 50 and the Model
VS-3000 from Spray-Tech were a natural fit. Steve and his colleagues visited
Polytek®'s facility where Angus Macaulay demonstrated the use
of Polygel® Spray 50 for creating a thin blanket mold. It was
decided that the mother mold for this sprayed Polygel® blanket
mold would be made from Poly Plastic 15-6 since it too is a 1:1 mix product
that could be easily applied in the field.
The advantages of Polygel® Spray 50
and the VS-3000 spray machine were clear. This unique, 1:1 mix, low-viscosity
liquid rubber mixes readily and flows into minute detail before gelling
to a thixotropic, workable state. No powders or additional liquid additives
are required for thickening. Since both the Part A and Part B are very
fluid liquids, they are easily pumped with low-cost portable equipment
such as the Model VS-3000. Polygel®'s patented, self-thickening
characteristic makes it ideal for vertical and overhung surfaces like
those encountered on the termite mounds, so runs and drips could be minimized
or eliminated. The spraying action itself provides for even better detail
penetration with fewer surface air bubbles than brushing alone can achieve,
especially on such a deeply textured pattern as found on the mounds.
"Being able to spray Polygel®Spray
50 was the solution to a previously impossible problem," Steve says. "It
also cut the labor cost in half and the material cost as well. And most
important, the quality of the mold was better than we could have hoped."
Steve's relentless research and planning resulted
in success. There was no room for error since the only available supplies
were those brought in. Forty-pound pails of liquid rubber and plastic,
the VS-3000 sprayer, brushes, gloves, releases, spare parts, a generator,
tools, scaffolding, and everything else needed for the several-week project
were transported to the work sites by Ghanian villagers whose services
were used for assorted tasks. As if the moldmaking itself didn't pose
enough of a challenge, negotiations with Ghanian officials, local landowners,
and port authorities helped to keep the Tobin team on their toes. |
