Slip Cast Stoneware

[Imaan]

Hello everyone,

 

I'm an Industrial Design student with no knowledge in ceramics. I need to cast a cup in stoneware and need help with that. I went to the ceramics department at my school but they didnt have any knowledge about slip casting stoneware. I really love the look and feel of stoneware and the cup I'm making will be assembled with injection molded parts so the tolerances have to be as tight as possible.. that's the reason I have to slip cast it.

 

Any help would be appreciated.

[PeterH]

Imaan,

 

The simple answers to your questions are are:

- slip casting a stoneware body is just like slip casting any other "pottery" body

- firing a slip cast stoneware body is just like firing any other stoneware body

 

Does your ceramics department do any slip casting? If so I would go back to your

ceramics department and ask how you could make your cup in whatever body 

and firing schedule they use. Most of the issues will be the same: making/finding

a mould; doing the handle; casting; and living with the shrinkage [and possibly

warp-age].

 

Eventually you will need to find a suitable casting body. You may find that some of

the features you find attractive in "stoneware" are fairly natural to hand-thrown

work but less natural to slip-cast work. (AFAIK it is harder to include grog in a

casting slip than in a throwing body, and the casting-against-a-surface process

itself tends to produce a smooth surface rather than a textured one.)

 

Regards, Peter

 

Can you give us more details about what you want to do. In particular phrases like

"the tolerances have to be as tight as possible" are far to vague. What time-scale

and resources do you have available?

[Denice]

I have purchased  stoneware slip at a local ceramic supply store.

 

  I remember it had a higher shrinkage rate than low fire slip.  The manufacture should have the shrinkage percentile information available.  Denice

[Imaan]

Peter,

 

Thanks for your help! Basically I need the outer dimensions of the cup to be as accurate as possible. I know it's not easy if not impossible to control the dimensions of the outer wall on the wheel (unless you're jollying). I think slipcasting would be best for my purpose since I can just make a mold and cast the piece.

 

I just need help with the slip recipe for stoneware. I'm aware that I won't be able to get the texture that you see on hand thrown pieces but I'm OK with that.

 

I have all the resources available to me.. The ceramics department said I can come in and use their studio for anything I need. I have 3 weeks to make this thing.

 

Denice, could you tell me the name of the manufacturer? I haven't been able to find any pre mixed stoneware slip.

 

Thanks!

[PeterH]

IImaan,

 

Your best bet it to but stoneware casting slip from a handy local pottery supplier. Failing that

you can make your own from some stoneware clay:

http://ceramicartsdaily.org/ceramic-supplies/ceramic-molds/in-the-mix-from-clay-body-to-casting-slip/

... although it won't work too well for some clays (things like grog don't suspend well the slip).

Notice that this is an except from a freebie Ceramic Mold Making Techniques: Tips for Making Plaster

Molds and Slip Casting Clay. Download that as well (you may need to register first).

 

Remember that you will get quite a bit of shrinkage (10-15% ballpark), and that any mould you cast will need

time to dry before you can use it. If you are going to make your own moulds, cast an experimental one today

(perhaps a drop-out mound from a smooth-sided plastic drinks cup [i.e. one from a cheap drinks dispenser]).

 

AFAIK handles are an issue, and are often cast separately and then stick on. Or are you doing this

bit in plastic?

 

Pleased you mentioned mentioned jolling, as this might be the way high-volume production might go

-- and IMHO impractical for this one-off. IMHO you should argue the case in any report you produce.

 

Regards, Peter

 

Obviously finding  a book or two on the subject would help. Do you have a library available? A good-ish

introduction is Sasha Wardell's Slipcasting.

http://tinyurl.com/ngbqvlo

... possibly cheaper via bookfinder

http://tinyurl.com/oc5so4n

.... enter your own postal region and currency in the search page.

 

[PeterH]

Can you give us some idea of the shape you are wanting?

 

If its very simple, you may find that you can cast your mould from a found object,

such as a plastic container.

[Biglou13]

"Tight tolerance"

 

Casting no biggie, stone ware body no biggie , firing no biggie

 

Tight tolerance now you have issues.

Even with calculated shrink rates, it won't be perfect.

 

You may need more time it get perfect fit.

Unless rest of structure is built around given object.

 

There are 3D printing companies that include ceramic end product.

 

Let's say you make a master, make a plaster slip mold, Make a green piece bisque it, maybe glaze it (another unknown), Fire piece ......it's off by 6mm here and 8mm here. Go back to start. Make a new master, new mold, dry mold, cast, etc etc....... Lather rinse repeat. Ok now add error to each step........and this is over simplified list of steps.

 

I'm not saying it can't be done. But your asking for a lot especially being uninitiated to pottery.

 

Given the technical nature of your project I'd go with 3d ceramic printing/mfgr

[PeterH]

Biglou13,

You have a good point there. Consider once cycle of the process you mentioned

Let's say you make a master, make a plaster slip mold, Make a green piece bisque it, maybe glaze it (another unknown),

Fire piece ......it's off by 6mm here and 8mm here.

Even carried out by an expert there is a great deal of essentially irreducible time: waiting for things to dry adequately; 

waiting for the next bisque/glaze firing; etc. Achieving all this in the 3 weeks Imaan mentions seems a tall order -- even

ignoring the repeat cycles needed and the delays inherent in a learning process.

 

Maybe a dependency chart with all the dead-periods included is in order.

 

Your suggestion of 3D ceramic printing for a prototype seems a potentially viable alternative, although presumably the

stoneware appearance may well be lost. Quite a lot of learning-experience on the lead-times of ceramic processes to

include in a project write-up thought (if that gets credits). Assumes availability of: a suitable 3D modelling service; 

suitable solid modelling software, and the ability to get up to speed on it quickly. I presume that a 3D modelling service

would have an accurate knowledge of shrinkage rates.

 

Regards, Peter

 

Just brainstorming. If you had to produce something in a time-frame that permitted one - but  only one - cycle, and had the

necessary skills, maybe you might stand a chance on the wheel. Throw many cups at slightly different scales, say 100% to

120-ish% of the desired final size (trimming against templates). Put them all through the two firings. Pick the best sized one.

Ugly, but if you need just one prototype ASAP ...

 

 

[JeffTimothy]

Just brainstorming. If you had to produce something in a time-frame that permitted one - but  only one - cycle, and had the

necessary skills, maybe you might stand a chance on the wheel. Throw many cups at slightly different scales, say 100% to

120-ish% of the desired final size (trimming against templates). Put them all through the two firings. Pick the best sized one.

Ugly, but if you need just one prototype ASAP ...

 

I was thinking the same thing.  Knowing the approximate shrink rate of the body you could potentially throw a number of versions at slightly different sizes and take the most accurate one in the end.  Without the dimensional accuracy requirement, it would be much simpler, even to go the moulding / slip casting route.

 

Jeff.

[Imaan]

Thanks for your help guys! Really appreciate it!

 

I went to a pottery supply store and they also recommended that I just throw it on the wheel. They said I can cut different templates to keep the outer shape constrained. The problem with that is I have 0 experience on the wheel and I don't know anyone who's willing to do it for me. Another question I had was how thick should the walls be if it's 3" diameter by 8" tall stoneware piece?

 

I'll go to the ceramics department again and see if I can find someone.

 

Thanks again!

[Mart]

Forget throwing Seriously.

Go back to your ceramics department and build it out of stoneware clay slabs. (unless the design is too complicated - btw, can you post a drawing of that cup?)

All you need is clay a rolling-pin, knife, straightedge and a simple small brush.

If they tell you they have no time to show you how, find a closest ceramics/pottery studio and attend 1.5-2 hour course where you can build your first prototype. Most studios have regular courses. This is probably the best/fastest way to get started and they have all the materials and firing available.