Basic Slip Casting 

Thanks for the kind words and thanks for watching my video!

@@CaptMike I'm using it for my Materials Science class. They didn't understand slip casting of ceramics, so I found your video to explain it for them.

@@michaelcaplan1589 If I can help in any way, please let me know.

hank you for watching!

Good luck with your slip casting. Let us know if you have question.

Exactly what I was thinking!

Thank you I'm doing research for a Christmas gift and this was super helpful

Thank you for watching!

Nos Vives Thanks, Captain Mike! Very informative!.

Thank YOU for watching!

Thank you for watching my videos!

Thanks for watching!

No problem Maria. Tomorrow I will get to work on obtaining that info for you.

Maria, you can start at Amazon for the Kiln fiber paper/blankets/liner, It comes in all thicknesses and lengths. As far as the slip goes, it depends on where you live as to how difficult it will be to obtain. I live in a small town in Georgia and I have to drive to Columbus, GA to get mine. It can be purchase on line, but the shipping might be a killer. Start here www.bigceramicstore.com/clays/clays-by-type/slip.html and do some research. As you will discover, it can also be purchased dry and you can mix it as you like. If you have other questions, please ask.

I the pot you are using as a mold is enclosed all around except for a small opening around the top, you will have to make a two part mold. If the pot is shaped like a flower pot, then when the plaster is dry (assuming the clay pot comes out) you will be in business as the clay slip will shrink as it dries and the molded pot will pop right out.

Depends om how dry the mold is and the weather. Usually, with fresh slip about an hour or until the slip looks to have formed about a 1/4 inch shell.

Roy, I have made only one video on how I make a simple plaster bowl mold for slip casting. There will be a video on two piece molds later.

Love it captain! Always a pleasure...

The grey liquid is liquefied clay called slip. It can be bought commercially or you can make it by basically adding water to your clay body. When you pour it into the plaster mold, the mold adsorbs the water from the "slip" and solidifies it back into the clay body. The result is a cast of the inside of the plaster mold.

@@CaptMike Is this clay food safe? Thank you.

@@mikekiske The clay is food safe when bisque fired and the glaze will be depending on the type. All glazes will state whether they are food safe or not. Most are.

@@CaptMike Thank you!

Iuse 3 sizes, but off hand I don't know the lengths. However, Don't worry about the bands being too tight. Use the smallest you can get around the mold. thanks for watching!

Never tried a double pour. Usually I just let the slip sit longer in the mold. After the slip is ready to decant I just pour it back into the slip container.

@@CaptMike ok, great, thank you!

If the final product is going to be a plaster duplicate of a plaster original, then I would make a mold from silicon or latex, depending on the subject. It is possible to coat a plaster master with enough stuff to keep it from sticking to the new plaster, but it is problematic. I have used cooking spray, Vaseline and Murphy;s oil soap to keep the second half of a two piece mold from sticking, but never tried to mold plaster to plaster. Unless the master is painted or something like that, I can assure you that plaster will stick to plaster. I will do a few experiments when I get a little time.

I"m going to use the mold that I make with ceramic. I just need to make a mold from a object that is made already out of plaster paris. So i'm thinking that if i paint the object first with acrylic paint then use cooking oil , I"m thinking it will work ok...lol with fingers crossed. That will be great when you get free time to do some experiments ... Thank you for letting me pick your mind a bit...

The only problem with pouring slip into a silicon mold is the lack of absorption. That's what the plaster of Paris does. It absorbs the water from the slip leaving a clay shell. You clan press normal ceramic clay into the silicon mold and it will dry faster. You have nothing to lose by trying the slip. It will just take awhile to dry. Another idea (I am working on this as we communicate) is to make a master (positive) by pressing regular modeling clay into the silicon mold and then sticking it to the bottom of a container and then pouring plaster of Paris over that to form a mold.

@@CaptMike hmmm I would love to see a video on your new idea you're cooking up and thx you. I'm not interested in making a clay shell. I want a full clay mold. Im making soap dishes btw. So either I can use modeling clay in the silicone mold or the slip.

Any clay item, bisque fired will work for slumping or forming glass. Well, at lest as far as the design permits. The bisque piece, once coated with glass release agent will stand the temps for glass work OK.

@@CaptMike Thank you so much. I'm going to have a go at this. I think my clay pieces insulated the glass too much, but doing a thinner slip cast piece will allow more heat to get through the glass. Super excited. :-)

@@helpforhedgepigs8461 Let me know how things turn out.

It depends n several factors, but mostly on how dry your mold is and the thickness of the slip. Under normal temperature 70-80 degrees F and average humidity my low fire slip obtains a desired thickness (shell) of about 3/16 to 1/4 inch in about 45 minutes; sometimes little longer. I live in Georgia USA. Demolding can be done as soon as the clay sip is ridged enough to be handled without deforming, usually 3 or 4 hours depending on the complexity of the molds. Slip can be left in simple molds overnight if you wish. Hope this helps.

I live in Elberton, GA. My shop is airconditioned so the high temps could play a big role. In a large mold I can leave the slip in for about an hour. Again, that depends on atmospheric conditions and how dry the mold is. What are the molds casting?

No they do not need any type of mold release. As you mentioned, the only time I use a release agent is when I am making the plaster old. Most of the time if the master is glass or plastic a mold release will be necessary. After the mold is made and dry all you have to do is pour the clay slip into it. As the slip dries it shrinks and pulls away from the plaster so you can remove the cast piece.

Lori, you cast clay slip in a plaster mold. If you do not fire the clay it will remain soluable in water and if the piece gets wet or bumped (it's fragle) it will fall apart.

@@CaptMike Thanks!

Here is a video I made on the subject. Hope it helps : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-A2euCZ1ESlM.html

I don't think the plaster would hold up. If yu try, make sure the plaster is completely dry and use a flat one piece mold, not a 2 piece where you pour the metal inside.

The plaster molds are designed for clay slip. If you pour plaster into the you will not be able to get it out. A two part mold will stick completely together. If you cannot get clay slip, you can make it from moist clay. I have two videos on how to do this ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-LN8w-DIEQLk.html and ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-p3uYvu7QlJg.html

@@CaptMike thank you for the videos, it would be great if I can create a silicone mold using the plaster molds I already have. learning step by step thank you again.

@@beatrizgrajales4181 I thank YOU for watching my videos. I wish you all the luck in your adventures. Glad to help where I can.

I don't. I just make sure thay are dry enough. Maybe some one else here has an idea if something like that would help.

If you are refering to the clay, you can get commercial slip (liquid clay) or make it by liquifying a clay body and pouring it into a plaster moild.

As best I can tell, water to plaster ratio, room temperature, and maybe the age of the plaster. I think I once read that using warm water would make the plaster set up faster and really cold water would make it set slower. Thanks for the idea. I will need to do a little experimentation.

Thank you it is really helpful. Feel free to share your experimental results.

You can start here: www.clay-king.com/slip-casting/slip-casting-molds.html or type "slip casting molds" in your browser and see where that takes you. Good luck.

If the craft shop sells bisque ware they usually have a kiln. Ask if the do and if they do not, ask if they know of anyone who works in ceramics. Usually anyone who has a kiln will fire stuff for you.

I reuse it. Thanks for watching!

I used industrial plaster. I pay about $9 for a 50 pound bag.

Theoreticality you can, but the time it will take for the evaporation will be lengthy. Normally a plaster mold absorbs most of the water and speeds the drying.

You only need to do one pour into a plaster mold. Pour in the slip. let it set for awhile (usually 30 60 mnutes) and pour out the excess slip. I usually let my molds set overnight, but at least until the clay is solid enough to be handled.

Thank you :)

By brown, do you mean inside the cavity? If I use my local clay for slip casting it always turns the inside of my mold brown/red. The casting will also be the same color. If you are using regular low fire clay slip purchased from a supply house, it usually will be grey in color and fire to white. Terracotta slip will be red. Let me know.

@@CaptMike sorry! That was a typo. What I meant to say is when I pull apart the piece, it's always broken in half. I measure the slip gravity everytime . I am starting to think it has to do with the mold itself. Do you ever find the slip being clogged in the mold? How do I make my molds better so they drain the slip properly?

@@vishakhabhargava4070 after you pour the slip out of the mold, how thick is the walls of the cast? Do you wait long enough for the cast to set up. If the clay is too soft it will come apart when you demold. Better to wait until you are sure it is solid enough. If you are using a small mold,the slip might clog, but should not with a larger mold. Mind telling me what you are trying to cast?

Most of them that are ceramic bisque (fired clay). You can color them with ceramic glaze or use various paints to color them.

Don't know anything about air dry clay slip, but if you can get it liquid enough it might work. What I would suggest is to first put some of the slip on the outside of the mold or on some plaster and see if it will release when dry.

If you are refering to the molded piece, the "grey" slip turnes white after bisque firing to cone 06. The plaster to make the molds, of course, is white by nature.

As far as I know, there is no additive that will speed up the drying process without adversely effect the clay body (please jump in if some one knows differently). It should only take about three days, depending on your weather conditions for the clay to dry sufficiently to fire. Try a test piece in your kiln after 3 days and see if it holds up. A clue to whether the clay is dry enough is if it feels the dame temperature as the surrounding air when you hold it in your hands.

Yes, I have put porcelain clay in a blender and added enough water to make it the right constancy. Don't add too much water as that will cause the mold to water log faster and your molding will not release properly.

@@CaptMike Thanks a lot!

Here is their FaceBook page. I don't know if they have a website. Go figure. facebook.com/Allison-Ceramic-Supply-1042812882433088/

Jerry, start here www.amazon.com/rubber-bands-molds/s?k=rubber+bands+for+molds

Good eye! That's Toby.

@@CaptMike Toby is a cutie! Hey thanks for the extremely informative videos, been learning a lot!

These are commercially produced molds. I bought mine here www.allisonceramicsupply.com/, but they are sold elsewhere.

I'm sorry, I don't understand what you are commenting on.

The material poured into the mold is called slip clay. It is a liquified form of a regular clay body like you throw in a potters wheel, only formulated to be porable.

Thanks for the comment Gypsy. If you could be more specific (what time in the video) you are referring to and I will try to learn from that. I am new to this RU-vid thing and am aware I make a lot of mistakes. However, I try to learn from my mistakes and produce an enjoyable and informative video. I will re-watch the video again and try to see where I make vague references. Thanks again for you input.

Just wish I had his artistic ability.

I was just going to say "If Bob Ross did ceramics".

Plaster of paris or plaster is what is used for slip casting. The plaster absorbs the miosture from the slip leaving a "shell" that will be bisqued.

@@CaptMike thank you for your reply. I just started experimenting with making my own moulds and learning that there are many types of plaster on the market, some not suitable for mould making. Like the kind you use to patch a wall, for example. I used plaster of Paris to make a few moulds and they turned out fantastic but when I used slip in them they didn’t form a shell and it was as if the slip curdled. So perhaps I need to try a different slip. But also making sure I have the right mould in the first place.

Hi David, I did not re-watch the video, but I guess I was referring to one piece molds vs 2 or 3 piece molds. In my experience a completely flat molding, regardless of how thick is a 1 D mold. A 2 D mold is one where you get detail on the top and maybe a little on the sides and a 3 D mold is one that completely detailed all around. this make any sense?

I should have addressed the time involved, but in my haste I sometimes forget stuff. I mix the plaster into the water until it has all mixed in, about 3 or four minutes. When there are no more lumps to be seen I bump the container a few times to dislodge air bubbles and then slowly pour into the mold. Depending on several factors, temperature, humidity and plaster/water ratio, it should start to set up within 30 minutes....sometimes faster. Anytime after it has solidified it can be de-molded. Some directions say as little as 30 minutes. It can still be warm, but no water sitting on top. It is one of those things you will have to experiment with a little.