Plaster Casting - Multi Part Molds

Plaster Casting - Multi Part Molds

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This slide show is going to take you through the process of duplicating a sculpture using a multi part plaster mold. In this case, it was a clay cow getting duplicated in a soft foam urethane. The materials needed include:

Plaster
Plaster bandages, fiberglass, hemp, burlap, or horsehair
Disposable gloves
A mixing bucket
Trash bags to line the bucket for mixing up plaster
Aluminum cans
Scissors
Duct tape
A screwdriver
Shellac
Chip brushes
Pam, mold soap, mold release, floor polish wax, Murphy's oil soap, or liquid vaseline to use as a mold release

This sculpture was made by Liz, another RISD student. This project was made possible due to the herculean efforts of Edmund Earle (kind of), Damian VanCamp, Lauren Kaufmann, and the brave RISD janitorial staff.

15 comments	Add Comment

Mar 23, 2009. 6:15 PMh3llo41 says:

i made a mold with light plaster (i didnt know what to buy), and it break when i try to take it out, i might have bout the wrong one. is light plaster the same plaster as used in here?

Jan 5, 2009. 4:58 PMzoe-australia says:

Hi, cow looks great! next time try embedding some hessian(old jute bagging) or shadecloth , or cut up pieces of flyscreen into the plaster and it helps to strengthen the plaster mold. If you cut strips of old hessian/shadecloth/fibreglass flyscreen, and dip it into the plaster then drape it across the mold sections it helps. For curved shapes, using a triangle shaped piece of mesh fabric works best as it will wrap around a curved shape better. Love the idea of using aluminium cans for shims, great way of avoiding thick shims distorting the final product by making thick ridges on the joints, that have to be sanded down. If you keep your shellac mix in a wide mouth coffee jar with a screw top plastic lid then any leftovers can be kept for future projects. Just make sure the thread of the lid and jar are wiped clean before closing otherwise it will stick so hard you will be cursing when you next try to open the jar. Should this happen use hot water on the lid to soften it and then get a good grip on the lid and strain yourself to open it. This is when a srong handed man is an essential in the workshop! LOL.

Jan 25, 2008. 8:50 PMBig Bubba says:

Great! I love cows. Me and my dad are obsessed with them and always saying "Moo!". I going to make him one of these!

Nov 30, 2007. 5:28 PMPatrik says:

There's some seriously missing steps here...

For starters, how the heck do you get your plaster mold off your clay original, especially the udder part, which seems to stick out in all directions??

Dec 1, 2007. 3:12 AM

bofthem (author) says:

Since the final casting was in soft foam, undercuts weren't a giant concern in this model. I just destroyed the clay model upon demolding. It just fell apart. It's clay, not depleted uranium. It took some cleaning, but every piece of clay came out of the mold.

Dec 1, 2007. 4:31 PMPatrik says:

That's what I assumed, but it would ave been nice to show some pictures of that part as well - or at least *mention* that's what you did.

I can just imagine someone trying to follow your instructions using a piece that they cannot or do not want to destroy...

Nov 30, 2007. 7:55 PMGarth Knight says:

......you...said...udder... . . (snicker)

Dec 1, 2007. 4:27 PMPatrik says:

I'd hate to see what would have happened if I had said "teats"...

Nov 30, 2007. 8:43 PM

T3h_Muffinator says:

What happened to the revolution?

Dec 1, 2007. 7:13 PMGarth Knight says:

realty happened. (work)

Dec 1, 2007. 8:06 PM

T3h_Muffinator says:

v_v That's alright, though! *pat pat*

Dec 1, 2007. 3:00 PMtrooperrick says:

I like it. But if you could, for a suggestion, to put up an instructable of how you cast something with the mold.

Nov 30, 2007. 8:43 PM

T3h_Muffinator says:

Jeez, man. You've got some serious molding talent...

Nov 30, 2007. 6:28 PM!Andrew_Modder! says:

..good instructable, but i honestly dont like the slide show at all.

Nov 30, 2007. 4:55 PMGorillazMiko says:

ooooh. cows. :)

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bofthem (HAR.MS)

I'm M@. If you know Prototype This, TechShop, The Best of Instructables, Show Me How, or AVPII: Requiem, you've seen some of my work and the cool stuff I've been involved in. I build and design and ma...