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Bob Coyle

Member Since 06 Jun 2013
Offline Last Active Dec 20 2014 05:17 PM

Posts I've Made

In Topic: How About Toothpicks For Spike Supports + Other Questions

17 December 2014 - 08:38 PM

As the toothpicks start to burn, gasses will be produced that may crack the clay. it depends on the overall configuration of the piece. My default advice, as usual, is to try a small prototype of what you want and see what happens when you fire it.

In Topic: Is There A Way To Distinguish Low-Fire From High-Fire Clay Piece?

01 December 2014 - 11:56 AM


You could put the whole piece into a larger bisqued high fire bowl and then fire to cone 10 and when it melts its all contained in the bowl.
Thats the only way to avoid a disaster

Like Mark says...  Long ago I thought it would be neat to paint pictures on the surface of some commercial tiles I bought. They looked like high fire to me, besides I was just firing to cone 6... what could go wrong.


Well when I opened the kiln, there were no more tiles, only blobs firmly melted into the kiln shelf. Betcha I don't do that again.

In Topic: How Much Do You Stay Within Glaze Limits?

21 November 2014 - 06:46 PM

I have pretty much given up on trying to use limits. For one thing, they are all over the map, depending on whose limit formula you use. In the second place, my experience has been that the real ingredients you use to conform to a limit, cause wide variations in glaze fit and texture.. even though they are almost identical as far as oxide composition is concerned. as John says, The only real way to get what you are looking for is to know a little glaze chemistry and  keep experimenting till you zero in on these characteristics.

In Topic: Input On These Cups/handles

19 November 2014 - 02:30 PM

The first one gets my vote, but I agree with Bezine... the handle could be a little less heavy.

In Topic: Input Would Be Great!

17 November 2014 - 08:38 PM



I also like the look of Rebekah's forms. To me, this is how a beer stein/mug should look. I threw several similar forms for the prototypes I put out. Some people liked these (the more classic look) and some like the obvious " hand built" look which kind of surprised me. So I will do both for the up coming beer fest.


The manganese glaze/slip on the handle is one I poster here a while ago. I got a lot of comments that said it was not "food safe". which may be true, but I usually don't make stuff people eat  or drink from. I think it is fine for a handle though. I fire to cone 5-6 and I have made sculptures with this stuff that were copper plated for four days in a copper sulfate /sulfuric acid solution and the glaze  didn't look like it was effected so it won't come off in the dish washer.

below is the formula is you want to try it.


Ingredient                  Parts
Rutile                       27.00
Red iron oxide          26.00
Manganese dioxide   20.00
Ball clay                   10.00
Flint                           8.00
Frit 3134                    6.00
Copper carbonate       4.00