# How to create plaster casts



## GobbyGruesome (Sep 14, 2005)

Great tutorial, Bam! Always impressed with how thorough and professional you are with your projects. Any risk of leaving the plaster in the mold for the full 24 hours? Aside from not getting everything done?


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## bamtunebam (Jan 1, 2010)

Nope, you may leave the plaster in the mold. Often I will make one final pour at the end of the night and retrieve it in the morning.


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## bamtunebam (Jan 1, 2010)

In forgot to mention the best part. The process is simple enough that my ten year old son does the entire casting and extraction by himself. I left for work today and by the time I returned he had eight more completed which is great because it frees me up to work on other props!


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## GobbyGruesome (Sep 14, 2005)

bamtunebam said:


> The process is simple enough that my ten year old son does the entire casting and extraction by himself.


Watch for the upcoming step-by-step tutorial, "Leveraging child labor for fun and profit".


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## talkingcatblues (Jan 30, 2009)

This is really interesting. Thanks for including all the details, especially the reminder not to clog up drains with the leftovers when you're cleaning up!

If you were going to make the whole skull, would you drill a hole in the top and fill in both sides of the mold clamped together? (Figuring the plaster is pretty light such that a solid plaster skull wouldn't weigh all that much.) Or would you make two halves and then join them afterwards?


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## bamtunebam (Jan 1, 2010)

So Cat, that is an excellent question. look that the photo below:









When I made the mold I also created a method to pour in the plaster. If you look at the bottom half of the mold there is a tube through the mold where the neck of the skull would be. To produce a full skull the two halves of the mold would be joined and secured. The neck would be tilted up and the plaster can then be poured in. The plaster is not expensive so a solid skull is not such a big deal, but they can get heavy. I've also experimented with sloshing the plaster around the perimeter. Sometimes it sticks to the walls of the mold and sometimes not, but what is cool is when you release the skull and it did not perform a perfect cast and/or it breaks, the results are still good because a broken skull only adds more atmosphere!


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## talkingcatblues (Jan 30, 2009)

Ha - I didn't realize that's what that part was. Thanks for pointing that out. 

This seems like a good way to be able to consistently and cheaply mass-replicate objects for a big project (especially once you add in the child labor!)

Looking forward to seeing what you're planning to do with all those skull faces.


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## Atiehwata (Aug 26, 2010)

Brilliant! Question: instead of plaster, how would the mold hold up to spray foam or another substance if properly coated inside?


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## xxScorpion64xx (Oct 15, 2011)

What is the ballpark price for materials?


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## bamtunebam (Jan 1, 2010)

Atiehwata the mold is very sturdy. I'm sure it would hold up well using spray foam. Just like you say there would need to be some sort of liner or spray to keep it from adhering to the walls of the mold.

This is actually an intriguing idea. The heads would be lightweight. I'm also wondering if using a liner like kitchen plastic wrap might work. The foam might have enough strength to stretch the wrap into the correct shape. Of course you would have a big problem if the plastic tore open during forming.


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## bamtunebam (Jan 1, 2010)

Scorpion, the largest expense would be the urethane for the mold. I believe I spent around $40 for it. The actual casting is very cheep. Each skull face only costs about $0.50 in plaster. A full skull might run a dollar.


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## EveningKiss (Sep 18, 2012)

Phew I looked online at the link... $97 a gallon *shutter* BUT Ive spent more on less....


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## bamtunebam (Jan 1, 2010)

The price listed by EveningKiss is for a gallon, but that is a lot of urethane. My project probably only consumed about a half gallon or a little more.


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