Beginner's plaster-casting, tips and info please!?

Question

I want to have a go at creating some plaster casts from latex moulds. Some tips please on the type of plaster to use (and where to get it!) and the process itself! Complete novice!

Answer 1

you can buy plaster at most hardware stores or building suppliers. Take about half of the final volume of water. Sprinkle (you can do that fast, but avoid lumps and so on) plaster into water until plaster starts not to sink into water any more. Then mix. Shake/tap container a couple of times to get airbubbles to rise. fill into your mold. Make sure before you even get started that your mold is firm enough and tight enough no plaster will run out the sides.
Let set. Maybe 20-30 mins or longer.

Unless you have a flexible mixing container, clean up immediately. Do not flush any water- plaster mix down the sink, eventually it will clog up all your drains. Let water/plaster mix from cleaning settle in a bucket, then you can pour the water off and discard the plaster into the trash.

Answer 2

Make sure you work in an area with good ventilation and where it is easy to clean up spills (stay off the carpet)!

Spray the mold with a release before you mix your plaster, because the plaster dries quickly. Spray outside.

If you're using a 2-piece mold, hold the parts together with strapping tape. It won't ruin your mold, it holds great, and it's easy to cut off the mold!

Just use plaster of Paris. If you are transferring it from the bag to a container, or you mixing up a lot, wear a dust mask. When you mix it up, put a little cool water in a plastic bowl and gradually add the plaster with a little bowl. (Don't use hot water because it catalyzes too quickly.) Mix with your hand, unless you're allergic. If you are allergic, like I am, you can use a stick, but a glove works too.

Pour the plaster into the mold, and then shake it or tap it (depending on the mold size) to get rid of all the air bubbles.

Let it dry before you remove it from the mold. The plaster will heat up, which means that it is catalyzing and setting. After it begins to cool down again, it will remain damp for a while. For larger, 2-piece molds, I let it sit at least an hour or 2. If you have the time, let it sit over night if it's a big mold.

Let the plaster completely dry before you paint!

You can also use gypsum cement, and it mixes just like plaster. I like it better because it is a sturdier material and I'm not allergic to it. It dries slightly gray, and I think paint covers it better.

Answer 3

Be careful when mixing the plaster of Paris so you don't stir in, or create, air bubbles. The best casts are made with plaster that has been thoroughly vibrated so trapped air rises to the top. The air bubbles in your casting will create weak spots that are more likely to cause fractures.

Answer 4

Try using plaster of paris, this allows you to create detailed work - available at any sizeable chemist.

(remember the casting process is exo-thermic (gives off heat) so be prepared to renew your moulds after about 15-20 casts (depending on the quality of the mould)

It can be lots of fun, so just have a blast

Good luck