Pottery Clay - Drying Potclays 1150

by By Heather Coleman
(UK)

I am an artist living in Devon and working with clay for about 10 years now. I mainly create small models or larger sculptures and vases and my work has found it's way in collections all over the world.

I searched the internet to learn more about pushing my sculpture skills on larger pieces and found your website really really useful, also especially the historic content. I have been very encouraged.

You recommend pottery clay Potclays 1150 ..and fired a small test sample but also created one of the which is an 18 inch tall nude woman which took me about 2 weeks to complete (see the image at the top of the main pottery clay page).

She sits in my kiln now drying very very slowly with , just the air in the kiln at cool room temp, however, she is developing cracks all over her in places I would not normally expect to see them as well as places I would, and although I am fairly experienced with clays I am a bit worried that Potclays 1150 might fall to pieces on me!

The 1150 pottery clay was amazing to work with, so smooth and like butter, modelled perfectly and I got the fine details I wanted.

Are there any particular rules to working with it that you could advise on since you are a master expert with this clay. My figure is fairly solid although I was able to hollow out some of the base I do tend to work quite thick on pieces I make. Perhaps because it contains no grog it does not like being used for modelling larger thicker pieces.

Help help help! I need some comforting in my pottery clay madness :-) LOL

I can send you a picture if you would like to see otherwise I will add a picture of her in a moment to my website at:



editors note - picture added to the top of the main pottery clay page of this site

Any advice you can suggest would be really appreciated.

Heather

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reply from Peter as follows

Wow, this is such a great submission, I want to get back to you straight away.

First, thanks for your kind words, makes it all worthwhile :-)

I looked at your site - I think your work is superb.

Rules about pottery clay 1150. You, for sure, know more about clays than me, Heather, but here goes. The cracking......... as you say, it is a specialist modelling pottery clay (fantasctic actually) which can be fired like any 'normal' clay - according to Potclays (it has a high ball clay content).

I didn't have a particular problem in firing mine apart from a large horse head which seemed to crack like Ruku (looked better for it). I tried to follow the 'rules' which were dry very slowly (part covered by a bag at first on a slightly damp bat - the bat slowly dries with the sculpt under the bag)......

Secondly issue is the even ditribution of clay - hollowed to no thicker than about an average of three quarter inches in any one place. Third, ensure totally dry before firing. Rushing means moisture = BAD. I am open to learning about this issue too.

Heather, this is important stuff for the website and I appreciate your contribution.

Let's work through this one together. Keep me informed.

Best regards

Peter

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reply from Heather

Thanks for your advice on the Pottery Clay 1150 clay which does confirm there is a lot of ball clay in there as I thought and perhaps talc as well.

We have decided to keep my figure in the kiln as she is already much drier than she should be for reversing the process too much and so have placed a number of dishes of water in there next to her to keep the air moist and
at least that will slow the process down :-)

Our kiln here is computer controlled (some folk have a great dislike--eeek) but ours is built out of an old medical imaging computer that was adapted so can control the temperature very precisely which is how we managed to develop the range of special crystal glazes we also sell on another part of the Dawnmist website:



My figure was created from a solid pillar of pottery clay because I initially decided to model her that way, not knowing really what I was creating until I was already part way through on the project so I could not plan ahead for hollowing out. The upper portion of her body was 3/4 complete before I had even thought how the base would look :-) I made her by removing the clay that did not look right and blending what did.

So in places she is 2 inches thick which is not unusual for me when working but I always run the risk of cracks.

I have been doing small sculptures for years, mainly within my own niche specialism of clay smoking pipes which are now known around the world but I want to try larger figures that take more time to work on and have the same kind of detail as the smaller ones I have made... but I have sort of reached my limit with pottery clays which is why I have been searching for folk with knowledge so I can perhaps learn of techniques, processes and pottery clays that I can then use to move forwards into creating things that I can only imagine at this time.

The sculptures you show, that you have done, are the kind of level I am aiming for either in small figures or perhaps eventually life size but there is a lot I need to learn first.

I see most people who do sculpture built frames which are pre-planned and then sacrifice the original to make a mould which is what you said you do.

I do not consider myself clever enough to do that part yet.. the thought of doing so much work on a figure and then loosing it when I do not have skills of making moulds on that scale is daunting! Yet having the right pottery
clay to sculpt with is so important and the 1150 was a dream to work with.

There must be some good materials out there specially for taking a perfect cast of the master model and I am not sure which one is best. I have experimented with various silicon rubbers but even those need a frame to support the mould. So I need more info or a book that explains
what people do.

When I found your website about 2 weeks ago I found a number of topics that you deal with very much in tune with what I was searching for but as you can imagine trying to find people with overlapping skills and techniques to compare can be difficult, especially since most only talk
to people if they pay a fortune to go on a course.

What does cut up for casing mean? What is the special casing that I ought to be using?

So much to ask!

speak soon
Heather

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Peter's reply

Heather, the 'casing' I refer to is the traditional 'block and case' method of the pottery clay manufacturers.

Andrew Werber describes it on his website (see link on main pottery clay page). It is, essentially, a 'block' mold made of plaster of paris. In the simplest type of sculpt with no undercuts you will have just one case molded in two halves(more complex will have either one block with more than two pieces - the extra pieces being called "loose lumps"), or several separately molded cased sections for arms or heads or musical instruments etc depending on the complexity).

A 'case' is essentially a mold of the plaster mold - so when the plaster block wears out due to the defloculent in the clay slip, a new block can be made form the case (nowadays rubber, used to be plaster).

Heather, thanks for your input, please keep us informed, this is important feedback.

Peter (admin)