The Hand Cast

We used 390-S2 for this particular procedure as we do for most hand casts. Very large castings (8 or more people) requires more time and a longer setting Accu-Cast™ (like IBG, LS-680 or 880) would be appropriate. You would obviously also need a larger mold, more impression material and more gypsum cement.

Here's a list of the materials we used:

One pound 390-S2
A tupperware-type container for a mother mold
Modelling clay (Sculpy or the like)
About 3 pounds of gypsum cement (Hydrocast, et al)

You will also need:

Super Glue (Cyanoacrylate)
Thermometer
A strong plastic bag or bucket for mixing the Accu-Cast™
A mixing bucket for the gypsum cement
An Electric Drill w/Jiffy Mixer (optional, Accu-Cast™ can be mixed by hand)
A smock (optional, to protect your clothes)

SUBJECT PREPARATION: Make sure your model(s) understands the procedure.

POSING: Ask them what type of pose they plan to do and have them do several "dry-runs" actually placing their hands in the mold and finding comfortable positions. Their hands are only in the Accu-Cast™ for about 3 minutes, but if they have assumed an uncomfortable position, it can seem like hours. Older people may prefer to sit with their hand(s) dangling to their side or between their legs.

Due to the nature of the casting procedure, it can be difficult to get gypsum cement up into the finger portions of the mold if the fingers are pointing upward. Air tends to get stuck there and the cement cannot fill them properly. These fingers appear to have been sliced off with a knife in the final casting, and most often requires a redo. Extremely careful pouring of the cement can overcome some of these problems, but it is better to avoid them in the first place.

One of the more common requested poses is the American Sign Language "I Love You" where the middle two fingers are bent toward the palm. This pose only works if the two middle fingers are actually touching the palm or if one is touching and both middle fingers are touching each other. This way, there is a hole in the mold between the palm and those fingers where gypsum cement can flow downward and air can flow upward. Two people holding hands is fine as long as the fingertips of the fingers pointing upward are touching the other persons hand.

The model's clothing should be adequately protected from the alginate, as neither it nor the plaster will launder out later.

If the model(s) have long fingernails, have them place a small amount of modelling clay (Sculpy or the like) behind their nails. It can be shaped to be attractive, but without it, the gypsum cement will be too thin and the fingernails on the finished casting will break off. The model(s) can put hand cream on, but nothing else.

Most flattish rings are alright, but very tall engagement rings will scrape the inside of the mold when removing the hand. Rings with lots of incised detail will tend to fill with Accu-Cast™ and not leave much detail behind when removed. If the ring is loose fitting, the ring may come off and stay in the mold when the hand is removed. Could be a good thing, or could be a bad one, but they can be very difficult to retrieve from inside the mold.

MATERIALS PREPARATION: Since we are working in a mold, the Accu-Cast™ can be mixed somewhat thinner than for other types of applications. Too thin, and the Accu-Cast™ won't be strong enough; too thick and you'll get a lot of air bubbles and voids. We mix ours about 4.5 to 1 (water weight to powder weight) when we are mixing by hand in a bag, or about 5 to 1 (water weight to powder weight) when mixing with a jiffy mixer and power drill.

We have found that mixing the Accu-Cast™ in a strong plastic bag is great. It eliminates a lot of cleanup and its less dusty. Weigh out the powder into the bag, weigh out the water (check its temperature) and pour it into the bag. Squeeze out as much air as you can, grip the top of the bag firmly, lay the bag on a table and vigorously massage it until smooth. Work quickly but carefully. When mixed, dump the Accu-Cast™ into your mold and begin.

You'll probably make a few mistakes the first time. Everybody does. Learn from them.

The Procedure (click images to enlarge)

Dump the Accu-Cast™ into your mother mold	If you mixed in a bag, squeeze the bag to get all the Accu-Cast™ out.	Remember that the hands will take up space in the mold, so don't fill it too full. The model(s) should assume their pose before going into the mold, because once they're in they won't be able to see their hands.

Have them go in...	...and push down until they can feel the bottom of the mother mold.	Then instruct them to come up about one-half inch or so. Also have them move from side to side a little to make sure they aren't touching the inside of the mother mold.

The Accu-Cast™ line will be a little higher on their arms than in the mold. Have them make a mental note of the height so they can keep from floating upward while the Accu-Cast™ is setting.	During the setting process, the model(s) may think they are touching the container. 99% of the time they are feeling the alginate stiffening around their fingers. Most people will say, "This feels WEIRD".	When the Accu-Cast™ has completely set, the models begin to wiggle their hands and then their fingers to release the mold from their hands. When air has reached the tips of all their fingers, they can begin to pull out slowly. Slow is the key to success.

Take this opportunity to look down into the mold to look for obvious defects. If it is really bad, its better to redo it immediately.	The little thin edge pieces need to be trimmed away before pouring. Make sure no pieces fall down into the mold. If they do, fill the mold with water and dump it out until the pieces of Accu-Cast™ come out.	Mix the gypsum cement medium-thin. It should be about the same consistency as pancake batter.

Pour the gypsum cement into the mold. If you pour it slowly onto the flat alginate surface many of the air bubbles in the mix will come to the surface and pop before getting trapped in the mold.	Its best if there is still a little bit of room left at the top of the mother mold so you can pour the gypsum cement above the Accu-Cast™. This will form an integral base.	When the gypsum cement has set (no less than 1 hour), remove the mother mold and carefully begin peeling away the Accu-Cast™. Don't go too fast because the gypsum cement hasn't reached its final strength and fingers can snap off.

This is a beautiful casting.	Note how none of the fingers was pointing upward in the mold (look at this picture upside-down)...	...and all the fingers poured up very well.
There is always at least a little bit of clean-up needed to finish these castings. Air bubbles can usually be popped off, voids need a little hand sculpting and the base often needs some smoothing off. X-Acto knives, popsicle sticks, sand paper and small chisels can be very useful for this. We use dental tools which are available through any of a number of dental supply catalogues. Check the internet. If you want to paint these castings, wait at least a week for them to dry sufficiently or the paint won't go on properly. Necessity is the mother of invention, but experimentation is its father. Let us know if you come up with any cool techniques and we'll post them here.