Making Slip for Slipcasting

This week at the studio, Otto talked about having made slip to use in plaster molds. A little piece he’d slip cast was on the work table when I came in. It’s been so long since I’d done any slip casting, it made me wonder what the ratio of clay to water should be, how it is made smooth enough to pour, etc. So, I found a couple of articles to share that concentrate on these aspects and more. I think the last time I did slip casting was with my Mom’s friend Nancy when I was seven or eight! Maybe it’s time to give her a whirl. Slip casting is a good article covering the process from start to finish and includes formulas. Basically, the ingredients consist of clay in dry form, water, water glass (sodium silicate). I’m a fan of and found some good information from one of their ceramic experts. He said, “any clay can be turned into a slip. Cut the wet clay up into small pieces and let it dry out completely. Put the dry pieces in a container and add water until it just covers the dry clay. let it sit, do not stir, you will be able to see the clay disintegrating as it absorbs the water. Within a few hours it will be ready, next day is better, mix up and use.” This is exactly what I wanted to know and I have some pieces I never bisqued for one reason or another. So, I think I’ll just break them up and follow Sam’s advice. Here is another site that gives good basic information. It is not an in-depth article, but covers the process of slip casting rather well. I cannot vouch for the veracity of the article, though, in terms of the length of time needed to mold a piece, because these articles have conflicting advice and I don’t know what to believe. Another article suggests 20-40 minutes, whereas the ‘another site’ article above says eight hours or longer, depending on the size. That sounds like an awfully long time. I guess I’ll just have to experiment and follow-up with Otto. I like the idea of slip casting something, then altering it to make it more of my own. Since a piece is leather hard when unmolded, I would still have the time to make changes. This video below on “Clay for the Slip Casting Process” gives more depth. Based on what this ceramist says, I would have to add a deflocculant like water glass or soda ash to make slip the right consistency. Also, I have to consider whether the clays I’m considering using are appropriate, a white and a red clay. According to the video, porcelain is a good choice. Because there are many questions still unanswered, I am going to have to ask the centre’s artist-in-residence more about slip casting to get a better idea and I will report what she says at a later time.

About Jan

I have a background in ceramics, graphic design and journalism.
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6 Responses to Making Slip for Slipcasting

  1. Marcos says:

    Hi there Jan!
    I would like to thank you for your help in this article about Making Slip for Slipcasting.
    I am planning to start my own studio, but prior to it, I am looking for some information about how to reduce costs, like building my ceramic kiln and slip clay.
    As I live near banks of kaolin and quartz(white sand), I am searching ways to produce clay for slip casting locally, saving on money and transportation.
    I’ve heard there are many different recipes for slipcasting, but I have not found a descent one yet, in which I may use both ingredients. Do you know a good recipe in which we use them? Would you recommend any?
    Again, thanks for your help! Hugs.

    • Jan says:

      Marcos, it sounds like you have great resources right at your doorstep. Wow, that’s great! I will ask a few people who know more about this than I do and report back to you by comment here. In the meantime, go to and post to their threads. It’s an active site and has very knowledgeable people on board. Good luck and I’ll be back! 🙂

  2. Marcos says:

    Hi Jan, how are you doing?! Thanks for your reponse.
    Well, I don’t live this near (right at my doorstep), but if I pay for I’ll get a load for a chep price. It could only be better if an oil well poped up at my backyard. lol
    I spent some time reading the website you have suggested me, but found none recipe yet. I even found a girl who’s also from Brazil and was looking for the same thing. You probably know brazilians are like lice: they are everywhere!!!
    Have a nice week. Hugs.

    • Jan says:

      Hi, Marcos! I hope things are going well for you in Brazil! I do have news for you and am waiting for the comments of one other person before I bundle them all up and send them to you! Cheers!

  3. Marcos says:

    Hi there Jan!!
    I want to thank you for your help. You are so helpful and kind…
    You said it was cold and rainy in Canada? I saw on TV it was raining cats and dogs during the F1 Grand Prix up there. But dear friend, here it is a bit cold too, cos it is winter time.
    I received your email with the experts’ answers and they helped me with their tips.
    I have decided to reply to your message here because I believe someone else could read it in the future.
    Besides all the information found in the blogs they suggested me, I plan to order the manual Slip (and What Every Ceramist Needs To Know About It) and the book
    Ceramic Formulas: The Complete Compendium. Probably They will be nice resources of info.
    Hope you have a better weather next weekend. Hugs.

    • Jan says:

      Marcos, you are so welcome and good idea about letting others see the info you’ve come up with. Joan was only too happy to help. It looks like you’ve found some good resources from the looks of it and I hope they give you the formula you need for your project. We’re excited about your venture and want to keep in touch with you about it as you progress… This weekend was splendid and it’s even a bit sunny right now… That’s right, it’s fall where you are. I can relate, as it’s felt fallish here off and on lately. Cheers! — Jan

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