plaster casting in the post-google age
August 25, 2024 1:41 PM Subscribe
I want to cast things (art objects) in plaster. I do not want to make molds out of plaster, but have a finished piece made of plaster. I cannot make Google understand this. Please recommend sources of information!
Books or in-depth websites would be great. I have lots of questions about the process and I want to learn more about the variety of plaster and plaster-adjacent materials out there. Most of what I can find about actually casting in plaster (as opposed to making molds with plaster) is very surface level, basic. I need like detailed beginning to end process instructions, technical details, explainations of different materials, etc.
Thanks in advance for any resources :)
Books or in-depth websites would be great. I have lots of questions about the process and I want to learn more about the variety of plaster and plaster-adjacent materials out there. Most of what I can find about actually casting in plaster (as opposed to making molds with plaster) is very surface level, basic. I need like detailed beginning to end process instructions, technical details, explainations of different materials, etc.
Thanks in advance for any resources :)
Google How to cast like Rachel Whitehead. Watch the video...and read the step by step process
posted by Czjewel at 4:20 PM on August 25
posted by Czjewel at 4:20 PM on August 25
Do you want to shape your object over a framework, or do you want to use a (eg silicone or clay) mold to create the plaster object? I have done both, neither is difficult.
An easy start is to make a cast of your hand. buy the cheapest kind of clay, enough to fill a small bucket. Coat one of your hands in Vaseline or Baby oil or cheap cooking oil. Form a Fist and thrust your hand into the clay. Gently pull it out. Clean Hand off and make the plaster. Or thrust an object in the clay. Whatever you do, make sure the clay is thick at least 3-4 centimetres, and you have an opening at the top to pour in the plaster.
Mixing plaster for art is the same as for diy. So follow the direction on the bag. Basically, use a smallish container and fill it with one cup of cold water. Now add one cup of plaster powder without stirring, until there is like a little peak or island visible above the water, add plaster as long as the island disappears (use a tablespoon, dont pour from bag). When a small final peak remains, stirr gently and slowly. It will have a pourable consistency, now pour into your clay mould.
It will appear hard quickly, 20 minutes or so, but is not cured so quickly. Plaster that is hardening feels warm. This is why you should use cold water, warm speeds Up hardening. Total curing (hardening) takes 4-5 days.
The Art teacher in this Video explains it Just Like my Art teacher did.
From the Same Guy, really good instructions
How to produce a mould and Cast in plaster
Of course you can get more sophisticated and make a silicone mould, which you the Cast with plaster
posted by 15L06 at 4:27 PM on August 25 [5 favorites]
An easy start is to make a cast of your hand. buy the cheapest kind of clay, enough to fill a small bucket. Coat one of your hands in Vaseline or Baby oil or cheap cooking oil. Form a Fist and thrust your hand into the clay. Gently pull it out. Clean Hand off and make the plaster. Or thrust an object in the clay. Whatever you do, make sure the clay is thick at least 3-4 centimetres, and you have an opening at the top to pour in the plaster.
Mixing plaster for art is the same as for diy. So follow the direction on the bag. Basically, use a smallish container and fill it with one cup of cold water. Now add one cup of plaster powder without stirring, until there is like a little peak or island visible above the water, add plaster as long as the island disappears (use a tablespoon, dont pour from bag). When a small final peak remains, stirr gently and slowly. It will have a pourable consistency, now pour into your clay mould.
It will appear hard quickly, 20 minutes or so, but is not cured so quickly. Plaster that is hardening feels warm. This is why you should use cold water, warm speeds Up hardening. Total curing (hardening) takes 4-5 days.
The Art teacher in this Video explains it Just Like my Art teacher did.
From the Same Guy, really good instructions
How to produce a mould and Cast in plaster
Of course you can get more sophisticated and make a silicone mould, which you the Cast with plaster
posted by 15L06 at 4:27 PM on August 25 [5 favorites]
There's also lots of different grades of plaster for different purposes that provide a variety of effects and longevity. You might also like to look I to jesmonite as a material.
posted by Iteki at 11:45 PM on August 25
posted by Iteki at 11:45 PM on August 25
I will add from my own experience:
Air bubbles are the enemy of your casting. A really simple way to get bubbles to work their way out is to use a cheap vibrator/personal massager. Turn it on and hold it in contact with the mold. It will help thick plaster move through the mold and help bubbles work their way out.
If you want to do life casting, I recommend alginate/moulage. There are two types: one-time use and multi-use. One time use is mixed with water to make a goo for making the mold. Multi-use has to be melted in a double boiler. It melts at 115F or so but will stay liquid for a decent amount of time. 115F is hot enough to give you a burn, so it needs to cool a bit. I stir it off the heat until it has the texture of pudding. You can make large thick molds with it, but that's wasteful and for the multi-use takes a long time to set. You can instead pour thick alginate over the surface and when it's set, reinforce it with plaster bandages*. These molds will cast plaster without needing a release agent and you will be able to see pores and fingerprints. It's really quite uncanny.
*plaster bandages are expensive: buy cheap gauze from a fabric store and cut it into strips. Mix a bowl of plaster, wear rubber gloves, and dunk the strips in the mix, squeezing out excess between two fingers. It's like doing paper mache.
For mixing plaster, I bought a cheap rubbery plastic mixing bowl from a discount store - even better if you can find one with a pouring spout.
I get the "add plaster to water" camp, but I had better experiences adding water to the plaster to get the consistency and quantity I wanted.
posted by plinth at 7:33 AM on August 26 [1 favorite]
Air bubbles are the enemy of your casting. A really simple way to get bubbles to work their way out is to use a cheap vibrator/personal massager. Turn it on and hold it in contact with the mold. It will help thick plaster move through the mold and help bubbles work their way out.
If you want to do life casting, I recommend alginate/moulage. There are two types: one-time use and multi-use. One time use is mixed with water to make a goo for making the mold. Multi-use has to be melted in a double boiler. It melts at 115F or so but will stay liquid for a decent amount of time. 115F is hot enough to give you a burn, so it needs to cool a bit. I stir it off the heat until it has the texture of pudding. You can make large thick molds with it, but that's wasteful and for the multi-use takes a long time to set. You can instead pour thick alginate over the surface and when it's set, reinforce it with plaster bandages*. These molds will cast plaster without needing a release agent and you will be able to see pores and fingerprints. It's really quite uncanny.
*plaster bandages are expensive: buy cheap gauze from a fabric store and cut it into strips. Mix a bowl of plaster, wear rubber gloves, and dunk the strips in the mix, squeezing out excess between two fingers. It's like doing paper mache.
For mixing plaster, I bought a cheap rubbery plastic mixing bowl from a discount store - even better if you can find one with a pouring spout.
I get the "add plaster to water" camp, but I had better experiences adding water to the plaster to get the consistency and quantity I wanted.
posted by plinth at 7:33 AM on August 26 [1 favorite]
The details of the answer will really depend on what you are doing.
A common use case is creating life casts of hands or other body parts. The way this is done in 2024 is by creating a disposable mold out of a jello-like substance called alginate. Searching the Internet for Life Casting With Alginate will lead you to all sorts of instructional videos and products. Part of the process is making the alginate mold. The next step is creating the final product with plaster. That second step will provide info on plaster, even if you're not doing a life cast with a single-use alginate mold.
Good luck, and have fun!
posted by Winnie the Proust at 9:35 AM on August 26
A common use case is creating life casts of hands or other body parts. The way this is done in 2024 is by creating a disposable mold out of a jello-like substance called alginate. Searching the Internet for Life Casting With Alginate will lead you to all sorts of instructional videos and products. Part of the process is making the alginate mold. The next step is creating the final product with plaster. That second step will provide info on plaster, even if you're not doing a life cast with a single-use alginate mold.
Good luck, and have fun!
posted by Winnie the Proust at 9:35 AM on August 26
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To reproduce an art object in plaster you need a mold of some sort...usually silicon or rubber...You coat the original in silicon several times...or enclose the object in a container that you will pour liquid silicon into. It will cure, then you separate the mold using a knife and remove the original object. Now you have two halves of silicon mold that you put together and now you can mix up plaster and pour it into the cavity. This is a simplification and there are many various ways to make a mold for plaster casting.
posted by Czjewel at 3:57 PM on August 25 [1 favorite]