Making a One-Piece Plaster Mold

Here is a short video on how to make a one piece plaster mold. It is for Bas-Reliefs and uses #1 Pottery Plaster with room temperature water. Recorded on December 13, 2012 using a Flip Video camera.

[@zippymontana]

John: Here's a trick (from Richard Notkin), after tapping the bucket with the mixed plaster to help the bubbles rise to the top, spray isopropyl alcohol onto the surface of the plaster in a light mist. The bubbles will all pop by changing the surface tension. Repeat a couple of times and you can get rid of a majority of the bubbles.

[@hobbypotter]

Okay John...{Gulp...I'm goin' for it!} You make it look easy and you've got me motivated!! Thanks so much...love your videos! Simple to understand instructions and definitely something I keep coming back to!

[@johnbrittpottery]

Excellent Grant- Thanks!

[@CarolynNooney]

you inspire me to do great thing! Thank you for sharing!!! Question: What plaster do you use and where do you get it?

[@Nancytoday]

Another all nighter of making plaster molds, eh! I do not know why I watch these and then have to work so hard afterwards! LOL, JK

[@johnbrittpottery]

Yes, adding old plaster will work, as will salt , as will hot water. Thx!

[@enemeriogalvan3361]

I like your idea you use to measure the plaster and water. It is much, much convenient...would it be possible that you can make a video on how make multiple part mold like for a footed bowl or footed vase??

[@johnbrittpottery]

Just cut a slab and push it in . Then wait for a bit (hour or so) and the plaster sucks out some water from the clay - shrinking it. It should come out easily. But the mold will take some time to dry when new. See other plaster videos which show this...

[@Nancytoday]

Thanks Grant, good idea.

[@raphvannerum3332]

NancyToday ong?6:-)a ndere draaimoddelln

[@33uptempo]

Thanks.....I'll give it a go.

[@33uptempo]

Is it possible to cast plaster into (hydrocal) plaster without breaking the mold or the casting when you take it out in order to make multiple castings? If so, which release agent would work best? I've been using silicone, which is great, but so expensive, for my bas relief sculptures.

[@proflooney]

I have a plaster cast I made and would like to cast a ceramics mold from it. What kind of mold release do I need to put on the plaster cast so I can pour my pottery plaster for making my slip mold

[@captmicha]

Do you ever use green sand molds? I was thinking of trying it for concrete crafts but am not aware of people using green sand for anything else besides just foundry.

[@BBBananas1120]

Can this method be used for making special FX makeup molds?

[@leahsoren9270]

John is the tile bisque fired or still wet? I love your videos! I think I’ve watched almost all of them. Thank you so much!

[@johnbrittpottery]

It is leather hard but could be bisque also. Glad you like the videos.

[@johnbrittpottery]

I will do it.

[@sophiemercedes1]

What kind of plaster do you use? I haven't been able to find an info on that subject. I use to take the one from school but never notice what kind it was. Thanks :)

[@johnbrittpottery]

#1 pottery plaster. Just google it. Ceramic suppliers sell it or sometimes builder do too.

[@johnbrittpottery]

For that you could seal the hydrocal since you don't need absorption to make it work. Try one and seal it with shellac or polyurethane.

[@carlrockaway1696]

what is the best clay to use for minimal shrinkage for making coasters?

[@johnbrittpottery]

@@carlrockaway1696 I would see what my supplier is selling cuz that makes life a lot easier and reproducible but you could also just add Grog to your clay body and that helps cut shrinkage pretty substantially depending on how rough you want it to be. But check with your supplier and see if they have a sculpture type clay . Another thing you can do is add coffee grounds or sawdust as long as you're kiln is outside and vented because that way it will have low shrinkage and the sawdust or coffee grounds or whatever will burn out. It's called a burnout body but you're kiln has to be vented or you create a lot of carbon monoxide fumes.

[@carlrockaway1696]

@@johnbrittpottery o ok, thanks for the information

[@kathbook]

Great video, what happens next? What is the best wat to push the clay into the mold and how do I get it back out?

[@jackson56180]

Most people use a casting slip for these molds

[@BBBananas1120]

Can this method

[@johnbrittpottery]

We use #1 Pottery Plaster but ???don't know what you have? Ask pottery supplier.

[@MrAlejo90100]

This is such a good video but is it possible for you to make a video for a one piece mold for a bowl or cup like this one? /watch?v=y7IXhgQdRkc

[@johnbrittpottery]

;-0