Plaster and Hydrocal: still the cheapest way to cast a lot of something

@moldmaker_mina · Oct 5, 2026 · 1.4k views
Difficultyeasy
Costpennies per piece

For architectural details, plaques, small sculpture and prototypes, gypsum products cost pennies per pour. Plaster of Paris is soft and chips. Hydrocal is harder and takes detail better. Ultracal is harder still and used for mother molds and tooling.

Mix by sifting plaster into water (not water into plaster) until an island forms, let it slake a minute, then stir without whipping air in. Pour into a silicone mold that has been rinsed with water and a drop of dish soap (surfactant helps it flow into detail). Demold when it is warm to the touch; it has set.

Seal finished pieces with shellac or acrylic before painting.

#plaster#hydrocal#gypsum#casting#cheap

18 💬 12 comments

12 comments

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@sparky_sal 16d ago

Bookmarking. I have exactly this problem and was about to pay someone.

11
@moldmaker_mina OP 15d ago

Should be the same procedure, the part moved slightly but the steps match.

1
@two_stroke_tom 15d ago

The embedded video is clearer than the official service manual, which is a little embarrassing for the manufacturer.

9
@moldmaker_mina OP 14d ago

Should be the same procedure, the part moved slightly but the steps match.

2
@applianceandy 16d ago

Can confirm, the cheap part is the one that fails. Replaced mine twice before reading this.

8
@stitchfix_sue 16d ago

Followed along, got it done in about twice the time quoted, but it is done and it works.

6
@moldmaker_mina OP 14d ago

Unplug it. Always. Takes two seconds and the worst case otherwise is a trip to the ER.

0
@rtr_watch 14d ago

Solid. Sending this to my brother who keeps asking me to fix his.

2
@moldmaker_mina OP 15d ago

Should be the same procedure, the part moved slightly but the steps match.

5
@two_stroke_tom 15d ago

Question: do you need to disconnect power for this or is it safe to leave it plugged in?

1
@moldmaker_mina OP 14d ago

Right around what the post says, give or take shipping.

6
@applianceandy 14d ago

Great find. Did not know this channel existed.

1

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