Thursday, 15 March 2012

A minor dilemma

Sometimes in ceramics we're faced with little dilemmas.."should I fire this lid in place and risk the glaze running off, or should I fire it separately, and risk it warping?" Yesterday, I was only firing to cone five, so I decided to place the lid of this carved box on the kiln shelf, as I didn't think the temperature would be high enough to warp it.

(btw, I've hidden the warp on this photo)

Wrong decision! Turns out the temperature wasn't high enough to make the glaze run, but the lid warped very slightly, so it no longer fits perfectly. Not by very much, but enough to be annoyingly noticeable. Hindsight is a wonderful thing, and now I'm kicking myself, realising that in this case, leaving the lid in place was most likely the sensible option.

Having said that, it's possible that it would have warped anyway, who knows. I'll try firing it again with the lid on and see if it settles down.

Here is another piece from the same firing:

Carved vase, approx 6 inches tall

This high manganese glaze was fired to cone 5 and has come out nicely with an even black colour and fairly shiny surface. Ideally, I would like to fire this glaze a little higher, between cone 5 and 6, but it's very difficult to judge accurately without a pyrometer.

Never give up..the best is yet to come!


  1. I like to fire my lids separate because I have always been annoyed with the clay showing just a bit at the meeting points and I can never figure out how to minimize that.

    1. Thanks for your comment, Linda. Yes, that can be a problem with this kind of design. For this piece, I'd brushed black slip on the inside so the join wouldn't show too much.

  2. Hello Mark---I always fire with the lid on. I have a small kiln so I need all the room I can get. I use a wax resist with some added alumina hydrate. It helps with any sticking (not warping.) It's an old trick mainly used in soda and wood firing. It's a nice carved box, warp and all.

    1. Hello Charlene, thanks for the kind words and tip, I'm fairly new to firing pieces with lids. Normally I'd be pushed for space too, but this time I didn't have much work to fire to this temperature.