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stepped inside of a bowl


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#1 Evelyne Schoenmann

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Posted 10 August 2012 - 02:16 AM

Hi all

I once saw a picture of a bowl, all stepped inside. I've read the ceramist put slip inside the bowl (up to the rim) and then took out (with a syringe) some of the slip again, waited for I-don't-know how long and then took out another syringe full and waited again... and so on. He got a very nice stair-like pattern inside the bowl. Now I can't remember where I've read that, so I tried it yesterday in my studio and the result was..... null.
Did anyone here try this technique once and can tell me how exactly to do it?
Would appreciate every help. Thank you!
Greetings from Switzerland

Evelyne

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#2 OffCenter

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Posted 10 August 2012 - 10:13 AM

Hi all

I once saw a picture of a bowl, all stepped inside. I've read the ceramist put slip inside the bowl (up to the rim) and then took out (with a syringe) some of the slip again, waited for I-don't-know how long and then took out another syringe full and waited again... and so on. He got a very nice stair-like pattern inside the bowl. Now I can't remember where I've read that, so I tried it yesterday in my studio and the result was..... null.
Did anyone here try this technique once and can tell me how exactly to do it?
Would appreciate every help. Thank you!
Greetings from Switzerland

Evelyne


I can't help you but you just probably solved a problem for me. Not long ago I started casting faux paper cups out of porcelain (See attached pic.) but didn't know how to cast to get different thicknesses for rims. For cups, not necessarily like the one attached, I could cast them upside down with a small hole in the bottom (which would be on top) and draw out the slip until almost at the rim then a little more and a little more, etc. THANKS!!!

Jim

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E pur si muove.

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#3 Evelyne Schoenmann

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Posted 10 August 2012 - 01:43 PM


Hi all

I once saw a picture of a bowl, all stepped inside. I've read the ceramist put slip inside the bowl (up to the rim) and then took out (with a syringe) some of the slip again, waited for I-don't-know how long and then took out another syringe full and waited again... and so on. He got a very nice stair-like pattern inside the bowl. Now I can't remember where I've read that, so I tried it yesterday in my studio and the result was..... null.
Did anyone here try this technique once and can tell me how exactly to do it?
Would appreciate every help. Thank you!
Greetings from Switzerland

Evelyne


I can't help you but you just probably solved a problem for me. Not long ago I started casting faux paper cups out of porcelain (See attached pic.) but didn't know how to cast to get different thicknesses for rims. For cups, not necessarily like the one attached, I could cast them upside down with a small hole in the bottom (which would be on top) and draw out the slip until almost at the rim then a little more and a little more, etc. THANKS!!!

Jim


You are very welcome Jim :D

Evelyne Schoenmann
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In love with alternative firing methods
www.schoenmann-ceramics.ch


#4 Chris Campbell

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Posted 10 August 2012 - 04:33 PM

On the original question ... Are you casting in a plaster mold, greenware?

And Offcenter ... Those cups are fabulous! They just look like a party is gonna happen.

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#5 Evelyne Schoenmann

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Posted 11 August 2012 - 06:58 AM

On the original question ... Are you casting in a plaster mold, greenware?

And Offcenter ... Those cups are fabulous! They just look like a party is gonna happen.


Chris

I would cast the slip in a plaster mold, yes. I would fill the plaster mold (bowl shape) to the rim in the inside, like a pot of soup, and then take out a bit of slip again after the slip settled on the wall, etc. (see my original question).
Do you know how it works? The time to wait till I can pull out another batch of slip from the inside of the mold is my problem. Either I'am waiting too long and then the slip would be too dry already, or I'am waiting not long enough and then the stepped rim won't appear.

Thanks, Evelyne

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#6 Chris Campbell

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Posted 11 August 2012 - 09:59 AM

I looked in my Lark book of mold making and slip casting but could not find any thing on your technique. They do say that getting the thickness right depends a lot on experience and intuition. One trick to test thickness is to gently blow the slip away from the edge to see the thickness.
Are you making your own slip? They have a whole section on how to get that right and include several recipes.

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#7 OffCenter

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Posted 11 August 2012 - 10:19 AM

Evelyne, I'm certainly no expert on slip casting, just beginning to try a few things myself. Maybe you should just keep experimenting with the process you describe in your first post. One variation of that process may be to fill the mold, suck all the slip out and let the mold and bowl in the mold dry, fill to an inch (or whatever) below the rim and repeat for each step. Good luck.

Chris, Thanks!

Jim
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#8 Lucille Oka

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Posted 12 August 2012 - 12:58 AM

I am trying to understand what you are after. If your steps are limited to the inside I take it that the exterior is smooth; that is, no steps?
Or are there steps on the exterior as well? All of this is quite possible to do. However you must tell me how thick is the overall wall thickness? Are the steps defined or just a faint definition?



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#9 Evelyne Schoenmann

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Posted 12 August 2012 - 02:31 AM

Chris: yes, I'am doing the slip on my own. Last time I tried to do this stepped bowl guess I used slip that was too thick and dried to fast in consequence. The technique I'am looking for is not the usual slip casting I guess. Hmmmm ...

Jim: that's a clever way to experiment further. Thank you for the idea!

Lucille: my problem is that English is not my mothertongue, and so I have huge difficulties to explain what I mean. The bowl would be smooth on the outside and stepped only on the inside, yes. Imagine a soup bowl, full of soup to the rim. That's how it looks when I use the bowl shaped plaster mold and fill the slip inside, to the rim. Now what I saw in the picture I told you in my first email was that the guy sucked out a small part of slip and let that stand on a table for about 20 minutes, then he sucked another small part of slip out of the bowl. He waited another xxxx-minutes and sucked another small part of slip out, etc. until no slip was left in the bowl. Everytime he waited those xxx minutes, the "new" rim got dry on the plaster wall. He had to wait longer and longer between the sucking out of slip, because the "over all"walls got thicker and thicker to the bottom. So when he took out the clay bowl from the mold (after I gues a few days!) the wall on top was very thin and on the bottom thicker because on the bottom was the "cumulation" of all the stepped walls. Awwww, reading this I wouldn't understand a bit what I mean. I attached a picture of something else, not the bowl I mean, but the technique is the same: outside smooth, inside stepped. The overall thicknes at the bottom I can't estimate. The steps themselfes (rim) would be approx. 0,2 inches and would be very consistent from top to bottom.

Thanks for every help! Evelyne

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Evelyne Schoenmann
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#10 ayjay

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Posted 12 August 2012 - 03:23 AM

Lucille: my problem is that English is not my mothertongue, and so I have huge difficulties to explain what I mean.


Your English is excellent Evelyne, I think I understand exactly what you mean, unfortunately I don't have an answer, but it seems that it is just a matter of timing.

I think you will just have to keep on experimenting unless there is some sort of mathematical formula to define a time between sucking out the layers.

#11 Evelyne Schoenmann

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Posted 12 August 2012 - 05:08 AM

Ayjay: well, thank you for the compliment:)
Unless one or the other potter here on the forum knows the time one has to wait between the sucking out, I have to experiment some more. If one day I will get a good result, I will tell you all how I did it.

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#12 Lucille Oka

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Posted 12 August 2012 - 05:26 AM

If you are new to this work, and I suspect you are. I recommend you get a book on making plaster molds as Chris has suggested. You will be able to familiarize yourself with the different types of molds, plasters, and material usage. You can also find moldmaking books at your library or on Amazon.com

By the way, it isn't necessary to have an accumulation of clay on the bottom for the final 'step'. The walls and steps can be even through out.



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#13 Chris Campbell

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Posted 12 August 2012 - 10:50 AM

A large part of the slip casting chapter in the book teaches how to make slips, which clays to use and the importance of getting the deflocculant right. It appears to be the most important key to success. How experienced are you at making casting slips? With your idea it would be very important so you don't end up with such uneven walls ( thin at the top, thick on bottom ) that firing would be a huge problem.

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#14 OffCenter

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Posted 12 August 2012 - 12:16 PM

Evelyne,

I think your original description of what you're trying to do is very clear. It presents an interesting problem to solve. I can't think of any way to do what you're trying without having the wall get thicker and thicker at the bottom (as long as the outside isn't stepped), but maybe that's not a problem. It would be based on very sound structural principles to have the bowl get thinner and thinner (and maybe more translucent) as you go up the wall of the bowl. Just keep experimenting. BTW, thanks again for helping me find a way to cast faux paper cups with rims thicker than the body!

Jim
E pur si muove.

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#15 Diana Ferreira

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Posted 12 August 2012 - 01:06 PM

Hi, I love the concept! I am a slip caster too.
To get a 'straight' step, you will have to top-up the steps. Remember, the plaster steals water out of the slip while it is in the mold.
So, although you suck out a little bit of slip, you need to watch the level, and add a bit as the levels drop.
I suspect that you will have to vary the time to remove slip with each step. In the beginning, when the mold is still quite dry, quicker, towards the end keep the slip longer before you suck some slip out.

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#16 Diana Ferreira

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Posted 12 August 2012 - 01:14 PM

And, I suspect that there will be a lot of cleaning up too, after the piece has dried a bit. I find that the plastic 'credit cards' work well cleaning slip surfaces. (Do this while the piece is still in the mold.) Or wait till it is bone dry, and use a small metal sheet that has a step cut into it.
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#17 Evelyne Schoenmann

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Posted 12 August 2012 - 01:26 PM

see post below..

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#18 Evelyne Schoenmann

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Posted 12 August 2012 - 01:28 PM

Hi again Lucille, Chris and Jim

I'am not experienced in slip casting and I never thought this technique of sucking out slip is called slip casting too. I will follow your advice Chris and buy a book about slips, which clay to use and deflocculants. Maybe my experience of two days ago didn't go well because I didn't use deflocculant in the slip? I only mixed clay and water together. I thought I can make that stepped bowl in no time, but I have to think again :rolleyes: and take my time to experiment some more. I thank you all very much for your ideas and tips. And I'am glad that we could help Jim at least. Love your cups Jim! I've found another picture to show you how the finished piece should look (that bowl in the pic is out of glass). Only I want to get more steps (stairs?) than only those 3.

Diana: just saw your posts. Thank you for answering. What you say makes sense to me, I understand everything you explained. Yes I think also that one has to watch the level and that one has to vary the time to suck out the slip. I will try and experiment till my hairs gone gray... I'am hooked now to the project. Will take notes and tell you when I got a nice result (or should I better say: IF?!). Your Deutsch is great Diana!!

Thanks again from Evelyne

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Evelyne Schoenmann
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#19 Diana Ferreira

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Posted 12 August 2012 - 01:40 PM

Hi Evelyn,
I can highly recommend this book by Sasha Wardell.
http://www.bookdepos...l/9780713676723

(I have bought a few moldmaking and slipcasting books, and found that this one was 'most accurate'. she did some training in a ceramic production factory in France. I was taught moldmaking by a German moddeller, and slipcasting from one of his customers that runs a little factory.)

Oh, and I visited your website. your work is beautiful! I have visited Berne a couple of years ago and it is a lovely city!
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#20 Evelyne Schoenmann

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Posted 12 August 2012 - 01:46 PM

Hi Evelyn,
I can highly recommend this book by Sasha Wardell.
http://www.bookdepos...l/9780713676723

(I have bought a few moldmaking and slipcasting books, and found that this one was 'most accurate'. she did some training in a ceramic production factory in France. I was taught moldmaking by a German moddeller, and slipcasting from one of his customers that runs a little factory.)

Oh, and I visited your website. your work is beautiful! I have visited Berne a couple of years ago and it is a lovely city!


Hi Diana

Many thanks for the link and the tip for the book of Sasha Wardell and also for the compliment for my works. Making nice ceramic pieces is my passion! Berne is a romantic city here in Switzerland. I'am living in Basel (north of Switzerland) though. Not so beautiful as Berne or Lucerne is. Greetings and again: Thank you! Evelyne

Evelyne Schoenmann
Studio: schoenmann ceramics
In love with alternative firing methods
www.schoenmann-ceramics.ch





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