This molding compound forms a rubbery elastomer within minutes of mixing with water. Captures impressive detail, while being flexible enough to prevent entrapment of the hand. It dries and shrinks over time, so it's not suitable for more than a few castings. I used ALG-390 from Special Effect Supply Corporation
, which is a 3 minute set alginate.
Many plasters are available for casting, you can even use the inexpensive local plaster you find in any hardware store. I used a particular formula called Hydrostone which features high strength, and high detail. This also came from FX Supply, as item HYD, and is a 20 minute set plaster.
I used 1/2 gallon jugs, 1/2 gallon juice bottles, and 2 liter pop bottles. The only difference was that when I needed to cut away the mold, the plastic juice bottle and 2 liter bottles were a little harder to cut.
A cold mold is uncomfortable, so start with hot water. By the time you get it mixed it should be at a comfortably warm temperature.
Machine screws and nuts
If you don't want to break the mold, you have to have something sticking out of the casting once it's hardened in order to pull it out. Can also be used to mount the finished piece onto another project.
Small pieces of cardboard
Used to hold the screws in place while the casting cures.
I used a cordless drill and one egg beater. A regular mixer should work, and for large batches a jiffy mixer (paint mixing drill attachment) is recommended. Don't plan on mixing this by hand as there isn't enough time. Also note that the plaster is abrasive and may damage the beater.
These materials settle and compress so they should be mixed by weight. However, the working range of the mixture is pretty good, and in a crunch I believe suitable result can be obtained from volume measurements which will be detailed below. I'm using a postal scale that can measure in tenths of ounces up to 10 pounds, which is the range needed for small hand molds and casts.
Containers & cups
You'll want to stage your materials, measuring both the water and powder into separate containers, and then mix them together. Therefore you'll need containers suitable for holding the pre-measured materials. The cups are useful for scooping powder out of the supply buckets.
Watch or Timer
You'll need to time the molding process fairly carefully to obtain good results, so keep a timer handy. When you're elbow deep in any project it can be hard to accurately judge time.
Used to cut the molding container top off, and later cut the container away from the mold when you want to break the mold.
Long sharp knife
I found it necessary to cut and level the top of the mold so the cardboard holding the screws was level. A knife long enough to cut all the way through prevents tearing the mold.
Used to cut the top off the molding container, and is more convenient than the box cutter for some containers once the cut is started.
Used for a variety of tasks, depending on your skill and the tool it may replace several of the other tools.
Plastic forks, paper towels
Not necessary, but you may want them on hand for various tasks, such as scraping hardened molding and casting materials off various surfaces, cleaning spills, etc.Please note that while the materials are not generally toxic (check with your supplier), you should not use any of these tools for food later.
You'll need a full table for your first time. It can be done in a smaller space, but room to work is helpful as you may be worried about time during the molding stage, and looking for a spot to set the water pitcher is a distraction.
A chair for the person whose hand is being molded is nice. People tend to shift their weight frequently when standing, which can cause a mold to be damaged while setting.
A utility sink is useful for later cleanup.
Assistants: This can be done alone, though in my case I had four eager assistants helping me by taking pictures, holding containers during mixing, and providing opportunities to practice my collision avoidance and balance during the process.