Slumping and firing

Make some support pieces out of the same clay, and make them cone shaped so that they are stable but the area in contact with the piece itself are minimal, so that if they stick to the piece, the damage is minimal. These are called sacrificial supports; the Tang Potters used them to support those wonderful horses and camels they made during the glaze firing.

Steve Bath UK

In article , Bubbles_ writes

Hi Steve!

I know what you mean, but if you imagine a clock-face disk, for example, with roman numerals around it - might not the whole face slump around the numerals? Or, if I turn it the other way, even if I do support it with "sacrificials", might it not slump anyway?

I haven't tried my theories out, as this clock is for my teacher's workshop, as her plastic clock died on her and I just don't approve of anything plastic in a potter's workshop, as long as the same thing can be made out of clay! :-D

I go on holiday in July, so I hope to have the clock all ready for her the last Friday lesson before I leave.

Marianne

So are you intending to fire it face down?

Is not the back of the Clock flat? or have you built it up.

The Clocks I have made have all been flat backed because the hanging provision is part of the case containing the movement

The current Kitchen clock at home is a fairly freeform flat shape, mounted on a black stained wooden panel with the movement held onto the panel by the shaft with the hands on it, surrounded by a wooden box with the hanging hook on that. Saves trying to build all that onto the ceramic.

Steve Bath UK

In article , Bubbles_ writes

I cheated this time and dug the pattern in, instead of adding it to. So, yes, intending to bisque fire face down. Will be worse with the glaze firing, though, as that has to be face up. I have made a collar around the whole face, for better dust-protection and deep enough to contain the clockwork.

see above

My clockworks have no hanging provision attached, so I figured on making that in the collar of the clock sides.

I have a cylinder with a face - and then I have a smaller box inside which will be closed to facilitate reopening to change batteries. The trouble is that this clock is going in a ceramics workshop, so it needsto be - shall I say - dust efficientl

When I do fire it "on its back" for the glaze firing, that will probably be my greatest slumping risk. I do make some supports now and then and can only hope I have onesto fit under the clock face so it stays flat.

Marianne

In message , Bubbles_ writes

Hi Marianne

I work in porcelain and fire to around 1250, mostly leaving work bisque. I really don't glaze much at all, and then only to use a good white tin glaze as a base for lustres and onglaze colours. Glazes really aren't my thing at all!

I often make pieces that really do risk slumping at high temperature. Years ago someone suggested using high temperature ceramic fibre as a support. I had to use this technique a couple of weeks back and it does work for me. I wondered if it might help you? Any way of packing the back of your clock with the fibre? It doesn't stick to bisque porcelain but I'm sure you'd need to keep it away from glaze. I wonder if Steve can add anything to this?

Regards Susie

That sounds like a great idea, Susie, but I have never seen that here in Switzerland. That might just be because I don't know what it is, though! Now I know, I will ask my teacher and mmy dealer about it. Thanks!

Marianne

In article , SusieThompson writes

That is a very reliable technique; I use pieces of Ceramic Fibre in between pots in a biscuit firing, but the one occasion I used it in a glaze, cleaning off the fibre remaining on the piece after the firing needed care AND a good respirator (very important that). I was using a fairly high iron clay, and firing to cone

9 right over in reduction, so that will have made it stick more than a straight oxidising electric firing would.

In message , Steve Mills writes

Thanks Steve. I'd forgotten to warn Marianne that ceramic fibre is a hazardous material. I always wash my hands carefully after using it.

I've been thinking through how I use the fibre, and I suspect that if I packed/supported something too rigidly with it, there could be the possibility that the clay might split if it was trapped in one position. The things I make tend to flex and move around in firing. Any thoughts Steve? Susie

In article , SusieThompson writes

You'd have to pack it pretty tight to do that; most CF shrinks noticeably during its first firing anyway (except 1400 grade), The current *body soluble* stuff (Calcium-Magnesium-Silicate) does as well, tho' it's not yet as good at high temperatures as the old stuff (Alumina-Silica).

For bisc. firing stacks of bowls I have been using and re-using the same box full of fibre squares for the last 10 years (true!). They stop them pinning each other together and cracking, I use 3 to a layer.

I'm away for a week now, see you all later.

Steve

Hmmmm - that puts a damper on this idea. My workshop is so tiny, I can't set off space for working with hazardous materials. Even my glazes are non-toxic - although they still stink when fired ;-)

I'll figure this out.

Thanks to everyone for the input!

Marianne