Bottoms becoming rounded in firing

Marianne,

I've been hobby-potting for only about 2 years now, so my experience is limited.

The technique I use is to leave a slightly thicker bottom wall on the form, and when it is leather hard, use a piece of abrasive cloth (find in the drywall section of the hardware store) to rub the bottom flat.

Hope that's useful.

Robert

Bubbles wrote:

Those are lovely Marianne! There was a recent post I found interesting on clayart where they were talking about putting feet on mugs. It seems that you could use this method to 'indent' the center of the bottom of your pot that would give you a 'foot'. I would use a wooden ball to tamp in the center of the bottom of you piece

I will quote "Imagine a little club with a pawprint about the same diameter as the bottom of your mug.

When the mug is leather hard and you have a smooth flat bottom, a series of gentle taps with the mallet will make the foot look indented in three spots along the rim and basicly concave.

You can also do this with a wooden or styrofoam ball wrapped with twine such that it creates a three spoke wheel, so that when you tap in, the twine makes the three dents along the edge.

no real trimming to deal with. The little foot sphere takes all of 30 seconds.

This type foot drains in the dishwasher. " Elizabeth Priddy

Thanks, Robert. I was thinking maybe that would help. I tried making them a little concave at early leather-hard, but that didn't seem to help. Cutting or rubbing might well help. Will try this.

Marianne

Thanks, D!

Thing is, I want the bottom to be flat on the table all the way round. Thus, making those 3 dents will make "holes", right? I guess I could try doing it a little further in - or maybe even just that the hitting will convince the clay to forget? ;-)

Hubby also suggested I make convex "lenses" that I set the pots on to dry and to fire, so that gravity will assist a little.

Marianne

is it happening during final firing or bisquing? if the latter, you can take a board and use spray adhesive to stick a piece of 220 grit sandpaper to it, then use it to sand the bottom of the items. use a dust mask.

if the former, you could use some sort of lap wheel. there are small stained glass laps, bit larger ones for lapidary uses, and really large ones for doing rims of bowls, for example.

here's one i made that i use for both flattening the bottoms of ceramic pieces, and rims of glass bowls:

Most often during bisque firing. Thing is, I am picky - and sanding leaves traces, in addition to often "rubbing out" my "stamp" on the bottom.

Marianne

Hi Bubbles, how about using a damp chamois leather stretched over a board instead of sandpaper. Andy

That wasn't exactly what I had in mind. Imagine a round ball of clay, take a hard round object that is much smaller than the ball of clay and tap it into the clay. You get a slight concaved indentation in the ball which now makes that part of the ball no longer round but on the edges 'flat'. I just posted what they had said to share the information and to show where I got the idea from. They are doing it on a flat mug around the edge that already exists to give 'feet' of a short. What I'm suggesting is creating something of a edge (rounded though it may be).

Ahhh - I see what you mean, now. But I have been concaving the bottoms when they are still flexible, but that doesn't seem to help much. Do you think thumping them at leather-hard will be more effective?

Marianne

Good idea, Andy - or at least after sandpapering to finish off with a slightly damp chamois. Must be careful about creating wet areas when they are that dry.

Marianne