Make a Simple Plaster Mold for Slip Casting

[@bunch8]

This is a good example showing another advantage of using metric for these calculations. Converting from mass to volume is a breeze. Nice summary of a simple mold. Thanks Ken.

[@PotterybyKent]

For water it is for sure! And it just happens to work out very well for getting the needed amount of plaster.

[@44oaks]

Just be a normal human being and use metric for everything.

[@mrdobalina3451]

I think this will become a new hobby for me 🙂

[@PotterybyKent]

It is fun!

[@theabristlebroom4378]

oh, I love your explanation about draft angles! Nice, clear visual demonstration! Your very dry "That's a bad day." made me laugh.

[@PotterybyKent]

Haha. Thanks! And yes draft angles can be a bit tricky to think about so glad to hear my explanation was clear.

[@anyaghadimi9890]

Thank you for sharing, very helpful tutorial :)

[@PotterybyKent]

Glad it was helpful!

[@Cassidy-po3ud]

For some reason, I couldn't leave a reply. I thought this was a good video, loved that you included a way to figure out how much plaster mix to use for the mold. I had wanted to reply about a substitute for Murphy oil soap. I saw someone from Australia used Walker Ceramics Soft Soap. (That's all I know about it.)

[@PotterybyKent]

Thanks! From what I understand, any non-detergent soap without extra additives should work.

[@sheenalittle4246]

This is brilliant. Thank you so much I will give this a go 👍

[@PotterybyKent]

That's great!

[@tatendamapisire1597]

keep up the great work you are doing

[@PotterybyKent]

Thanks so much!

[@carlospinheirotorres9499]

I would assume that bubbles having a longer way to the surface, a tall container is indeed worst at releasing air from the dough. Regarding the releasing of the inner cup, I reckon that filling it with hot water would make the plastic pop out nicely. Oh, and about the "not starting the reaction untill stirred", whenever I hear that I think that doesn't make much sense to me as the chemical process is the plaster with the water... oh... and from what I understand, the "half an hour" for the heating stage is not the stage itself (which by the table is roughly 10') but the total time elapsed since you set the whole reaction in motion-i.e. when the plaster takes the dive... but I digress and at length 😅 from what I was here to do in the first place but somehow was unable to leave my thoughts to myself: Thank you for putting the time to share this, some good vicarious empiricism to be put to good use ♥️

[@PotterybyKent]

The timing and "starting" has something to do with the kinetic energy imparted by mixing from what I've gathered. I'm not sure about the details. As far as releasing, as you'll see in follow up videos, you actually want something very cold (not hot) so the PLA shrinks just a bit.

[@fredsnava]

Great! Thanks!

[@PotterybyKent]

You're welcome!

[@barkleyhunt9004]

thanks great video

[@PotterybyKent]

Thanks!

[@AIA3312]

Thanks for video. Can I use silicon mould for slip casting?

[@PotterybyKent]

People use silicone to make plaster molds. But you can't pour slip directly into silicone since you need to special properties of plaster.

[@CarlosLique-d3k]

Hi Thank you for your tutorial. I am interested in making some moulds for concrete plant pots , I intend to use a mix of white cement, plaster of Paris and white sand. Do you think a plater mould would be adequate for this concrete mix or I should use silicone moulds ??. Thank you

[@PotterybyKent]

I don't know anything about concrete planters. This channel is about ceramics.

[@phanlee4621]

I think clay mud will sink when it dry, easy to release and concrete will expand when it crystalize, hard to release form mold, may be you have to destroy the hard and bind well with concreate plaster mold. o for concrete, you'll need different kind of mold material ( wood, cardboard ? and build up layer by layer ??, plastic? silicone? for just casting? I Guess?

[@beverleybender1814]

I want to pour a mold to match my Rosenthal Baroness China bowl, what slip do I use for this fine china?

[@PotterybyKent]

No idea. Companies often use clay / slip that they design themselves.

[@beverleybender1814]

@@PotterybyKent

[@pisdihly]

Amazing

[@PotterybyKent]

Thanks!

[@scrapbooksiren1608]

I have vintage molds from 1978. 2 piece molds held by rubber bands. I used to cast low fire ceramics cone 06 and fire in my kiln but now live where I can’t use my kiln. I cast some yesterday with high fire slip cone 10 and it’s not releasing. These were molds I’d miniature food. Not sure I’m saying this right but does the cone of the slip make a difference in the release in the molds? Does low fire have less grit than mid or high fire?

[@PotterybyKent]

I'm not an expert in clay body materials, but yes they do have an impact. When I started, I was making slip from cone 6 throwing clay and often those parts would be "sticky" and not easily release. So I don't think it's so much the firing range, as it is the overall composition of the clay itself with the different types of component clays (which also change with firing temp).

[@loganwintry9945]

Did the sides cure faster than the inside? I'm confused on how that didn't form a solid block and instead got a near perfect pot

[@PotterybyKent]

The plaster is absorbing the water from the slip which results in the slip depositing on the edges. That the magic of slip casting and plaster!

[@doy470]

Can I use regular plaster?

[@PotterybyKent]

Not without some issues. My video from this past weekend talks about this.

[@meggysuitiful]

If your plastic container has a plastic label you can't remove , will that be an issue? It wouldn't seem so once the plastic was coated with wood soap.

[@PotterybyKent]

If it protrudes from the surface, even a tiny bit, then that would likely transfer into the plaster (and your pot). But as a way to get started I'm guessing it would be good enough.

[@meggysuitiful]

@@PotterybyKent The kind I refer to are sprayed on so appear to be part of the container. I'll give it a try! Thank you.

[@englishnerd2243]

So, when the final product/planter dries, it just sets out at room temp? For how long?

[@PotterybyKent]

You let it dry until it is bone dry - how long depends on the piece and your temperature/humidity/etc. You then bisque and glaze fire it to turn it to ceramics just as if it was made with hand building or wheel thrown.

[@englishnerd2243]

Thank you for your speedy response Kent! Do people often "rent time" at places that have a kiln? This is all so new to me. Thank you!

[@PotterybyKent]

Sure thing! Yes, some pottery shops and studios will rent out space in their kilns. There is also www.kilnshare.com/ And likewise you can join a studio to take lessons or do pottery there.

[@Zeynab.Emerald]

Hi! thank you for tutorials! I have a question! I dont have access to morphy oil. Is there anything as a replacement? For example, olive oil?

[@PotterybyKent]

I do not know what else might be commonly used, but it is a soap. So if you were to try an alternative, maybe liquid soap.

[@Zeynab.Emerald]

@@PotterybyKent thank you 😊 🙏

[@epidian6240]

Mydło szare ( kostki zetrzeć na wiórka) włożyć do garnka dodać mydła technicznego i gotować razem co jakiś czas mieszając po ostudzeniu dodać olej może być maszynowy i wszystko miksować do konzystęcji majonezu. Proporcje dwie kostki mydła szarego wagi 200 gram każda woda około 0,8 litra i technicznego 100 gram gotować około 3- 4 godzin

[@Cassidy-po3ud]

I saw someone from Australia used Walkers Ceramics Soft Soap. (I don't know if that helps you, but that is what I have seen.)

[@szyszynka1189]

Any idea what else could be use instead of murphy soap? It’s not available in my country

[@PotterybyKent]

I'm pretty sure you want a non-detergent liquid soap (so one made without artificial chemicals). However if anyone here in the comments knows of alternatives, I'd be curious as well.

[@ryancarlson5838]

What kind of plaster. The art plaster I can buy locally seems quite soft. Is it a special kind of plaster?

[@PotterybyKent]

It is USG number one pottery plaster. It is specifically designed for ceramics applications. I'd recommend going to a ceramics supply store - they should have it (or the local equivalent if outside the US). Beyond that, as far as hardness goes, one of the factors influencing the strength of plaster is how hard it is mixed (more vigorous leads to harder plaster).

[@karenleguilcher3956]

Hi Kent From where did you get the stirrer

[@PotterybyKent]

It's this one: amzn.to/3R4hRGK

[@jameswollman9803]

So to confirm, when done mixing, 3Kg of plaster and 2.1L of water will give you 3L of mixture?

[@PotterybyKent]

Yes, that is correct.

[@epidian6240]

Formy obrotowe robi się na kole , szkoda że nie masz. Ja już od 20 lat zajmuje się robieniem form gipsowych do odlewu i formowania ceramiki zawodowo

[@PotterybyKent]

I like my process!

[@epidian6240]

Dokładnie radzisz sobie dobrze ale można lepiej, czy umiesz zrobić foremkę na czajnik , albo formę do bateryjnego odlewu uszek do filiżanek czy kubków

[@SprayGuitar]

What if your cup doesn’t float ? 😂

[@PotterybyKent]

If it captures the air pocket inside, it will float for sure!

[@itsmeHiImtheSigridItsme]

You lost me at the air compressor 🙄

[@PotterybyKent]

Try it without. I only use it occasionally. Some forms are easier than others.

[@itsmeHiImtheSigridItsme]

@@PotterybyKent Thanks for your answer, I'll give it a try then! Also, I was wondering if I could try and cast a glass shape? (did I miss the part where you talk about that?)

[@PotterybyKent]

Check out my two part video in the playlist!

[@carlospinheirotorres9499]

​@@PotterybyKentI had honestly never thought about using this route but sure is handy knowlege for some of the more sticky situations (pun absoulutely intended)