Page 150 - Casting of Angels- Dave Parvin

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storage container (hereafter known as probably wasn't necessary but it did doesn't have time to react with the
the "mother mold") to a depth of make a sixth side to the mother moisture in the alginate, which would
about 1 inch by putting the empty mold. cause bubbling. To estimate the
mother mold on the scale and After about three minutes the amount of material needed to fill the
weighing how much water it took to alginate had gelled. I waited several void, I weighed the reassembled
get the 1 inch. (Note: mixing the more minutes to allow the top layer to mold, filled it with water, and
alginate into the water hardly gain additional strength and then took
increases the volume). In this case, 2 the mold apart. The top just lifted off.
pounds of water was just about right. It can be a problem to get the alginate
I poured 2 pounds of cold tap water out of the mother mold because it is
into one of the mixing containers. held in by suction. The best solution
(Another note: the gelling time of is to drill a small hole in the bottom of
alginate is inversely proportional to the mother mold and blow in
the water temperature. Since I wasn't compressed air. Once I had the
concerned about comfort for the dead "brick" of alginate in my hand, I
fish, cold water provided several gently pulled the top from the bottom;
more minutes working time than they separated easily and cleanly. I
warm or hot water would have). The removed the fish and rinsed out the
consistency you want for the mixed mold with water.
alginate is about that of thick pancake
batter. While water/alginate ratios CASTING THE FISH
vary with different brands, 5 ounces Now All I had to do was fit the two
of alginate per pound of water is parts of the inner mold together, slip
probably going to be pretty dose in them into the outer mold and I would Pour the mixed alginate into the mother mold
most cases. I weighed 10 ounces of have a void the size and shape of the and smooth it out with your fingers.
Moldgel Regular Set Alginate into fish with excellent surface detail that's
another container. just waiting to be filled with some
I dumped the alginate into the permanent material. There is only one
water and mixed with the electric problem - there is no way into the
mixer for about one minute. void since the fish was completely
Remember to always mix powders to surrounded by the alginate solution.
liquids and not the other way round or In order to provide an inlet, I took a
all you will get is gooey lumps. I then 3/8-inch drill bit and made a hole into
poured the mixed alginate into the the topside of the inner mold at the
mother mold and leveled it with my highest point of the fish void. The
fingers. I placed the fish on its side size of this hole is determined by the
and gently pushed it half way into the viscosity of the casting material.
alginate. Since the fish and the Since I was planning to use a urethane
alginate mixture have about the same resin which pours as easily as water,
specific gravity, the fish showed no the hole could be quite small. The
tendency to sink or float up. I took location of the hole is at the highest
several pieces of the plastic pill tray point to prevent trapping air, causing
and pushed them into the alginate. voids in the final casting. For some Plastic pill tray pressed into the alginate makes
These will act as keys to ensure the irregular shapes, it might be necessary good alignment keys.

mold halves will fit align precisely to drill one or more small holes to
when casting. These did tend to float vent air which otherwise could be
up so I held them in place for just a trapped. I then cut a larger hole in the
couple of minutes until the alginate lid so that I would be able to pour the
gelled. I then pulled out the plastic resin into the opening in the alginate.
pieces. Now I was ready to go back to the
By just looking, I estimated that first of this paragraph and proceed.
it would take about twice as much One of the advantages to
mixed alginate to fill the mother Moldgel brand alginates is that they
mold to the top as I had mixed for are formulated to be compatible with
the first layer. I measured 4 pounds fast set urethane resins allowing for a
of water and 20 ounces of alginate, light, strong casting with excellent
mixed them, and poured them into detail and minimal bubbles. The resin
the mother mold filling it almost to that I selected was Easyflo 60 Liquid
the brim. I took the lid to the mother Plastic made by Polytec. I chose this
mold and, turning it upside down, particular resin from others I keep in
pressed it in the mother mold until it stock because it sets up in just a few With the bottom layer gelled, mix and pour a
touched the alginate. This last step minutes, so quickly in fact that it top layer, nearly filling the mother mold.