Anyone who thinks that moldmaking
and casting is something that only the big kids can enjoy should read
on. At St. Paul's Lutheran Church (south of Allentown, PA), children who
were enrolled in a summer Vacation Bible School program got their first
taste of moldmaking and casting—and what fun they had! Each of 35 children
made a Hydrogel® N alginate mold of their hand in a single evening
during their craft session. There were four different age groups that
rotated through the molding process every 20 minutes. In under an hour
and a half, 35 molds were made and prepared for casting. Here is how it
was done.
Approximately 1 gallon of mixed Hydrogel® N, Polytek®'s skin-safe
alginate molding compound, was prepared at a time. Hydrogel® N is
an easy-to-use, dry, white powder that, when mixed with room-temperature
water (~1 part water to 1 1/4 parts Hydrogel® N by volume), yields
a creamy liquid with a working time of about 5 minutes. For the smallest
group (7 children), two 1-gallon batches were sufficient to make all the
molds. After the Hydrogel® N was mixed by an adult using a Turbo
Mixer attached to a variable-speed drill, each child was allowed to dip
their hand into the mixing container, then extract it, allowing a thin
layer of Hydrogel® N to remain. An adult then rubbed each thinly-coated
hand with their own so as to remove any small air bubbles which may have
been against the child's hand.
Next, each hand that had been coated was suspended into a clean metal
quart can. Hydrogel® N was subsequently poured into the cans while
hands were suspended, filling up to the level of the child's wrist. The
following phase was the most challenging: keeping the children's hands
still for the next 4 to 5 minutes while the Hydrogel® N turned into
a flexible rubber. It was surprising how well everyone did, with the exception
of one participant who apparently enjoyed wiggling her fingers through
the creamy liquid as it began to gel (this actually must have felt quite
good!).
After repeating this process for each of the four groups, the molds were
complete and ready for casting. Pottery plaster was chosen because of
its low cost and the fact that the kids could easily paint it if they
chose to do so as a final step. Enough plaster was mixed at once to completely
pour all 35 hands. Liquid silicone rubber such as PlatSil® 71-10
or PlatSil® 71-20, wax such as Poly Wax 15, or any "water-insensitive"
casting material could have been poured into the damp Hydrogel® N
molds. Within an hour of pouring, the molds were removed from their cans
and hands were demolded. The bottom of each can was removed with a can
opener to allow the mold to slide out easily. The soft Hydrogel®
N molds were split by hand and peeled apart, revealing 34 nearly perfect
plaster hands (not including our "finger-wiggler").
Needless to say, the kids thought this was thrilling. I have heard many
stories about the hands since the project. Some are on mantles, some are
in bedrooms, some have been painted, and one is even being used as a ring
holder. Adults could even use them as business card holders…think of all
the possibilities. For more information on how you can have fun with Hydrogel®
N, contact any Polytek® representative at (610) 559-8620.
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