Stephen Grimmer on fri 4 feb 00
Peter,
I'd bet that it's the Iron Oxide in the O'Hata Red, not the bone ash,
making it so prone to cracking and peeling in the raw state. I've noticed a
real flotative effect from RIO in celadons, temmokus, and iron reds.
steve
--
Steve Grimmer
Bowling Green State University
Bowling Green, OH
----------
>From: Peter Jones
>To: CLAYART@LSV.UKY.EDU
>Subject: Re: glaze problem
>Date: Thu, Feb 3, 2000, 12:19 PM
>
> ----------------------------Original message----------------------------
> Don: The first place I'd look for the settling problem culprit is your
> flint (silica). It is usually available in two different mesh sizes: 325
> and 200. They are eseentially indistinguishable to the naked eye, yet the
> 200 mesh would settle out much faster in a glaze. 200 mesh is generally
> reserved for clay bodies while the 325 is intended for glazes.
>
> The flint most potters use is from the US Silica Co. Unfortunately, you
> need the code on the bag to determine which is which. The code numbers
> don't match the mesh size. The code numbers are either 52 or 75. The 52
> batch is 325 mesh, the 75 is the 200 mesh. It is highly likely that someone
> at your clay supply company either didn't know the difference themselves or
> just substituted the 200 mesh if it was not specified which one you wanted.
>
> One thing you might try as a stopgap measure with the glaze you have already
> mixed up is to add about 1% epsom salts (of the batch weight) to your glaze.
> The salts help to keep your glaze in suspension. It may not work as well
> with all that heavy flint in there, but it is worth a try before dumping the
> entire batch.
>
> Your Oribe glaze might be working better because of the bone ash in it. I
> use only one glaze with bone ash (O'Hata Red) and it is so plastic that it
> nearly flakes off the pot, a real pain in the neck. For some reason,
> unbeknownst to me, it seems to keep things in suspension much better.
> Perhaps someone knows the reason why it acts that way.
>
> Hope that helps.
>
> Peter Jones
>
>
>
> ----------
>>From: Don Lyons
>>To: CLAYART@LSV.UKY.EDU
>>Subject: glaze problem
>>Date: Wed, Feb 2, 2000, 4:58 PM
>>
>
>>----------------------------Original message----------------------------
>>The Lexington Arts and Crafts Ceramic Guild is having a problem with
>>our celadon glaze, which has always been fine in the past. It has
>>settled into an extremely hard mass soon after making it. Thinking that
>>a mistake was made in measurement, a second batch was carefully made but
>>the same settling occured. It seems impossible to bring it to the normal
>>consistency, though a very small amount was obtained and tested. The
>>test, done in a test kiln, was normal. We fear that one of our
>>chemicals was either mislabled by the supplier.Could one of the
>>ingredients have a larger than normal mesh size and be responsible for
>>the settling? The formula follows:
>>Custer spar: 41.5, Whiting: 8, Strontium Carb: 9.9, EPK: 7.8, Flint:
>>32.3, Bentonite: 2, Red iron: 2.
>>Any ideas out there?? We've tried the usual. Our oribe glaze has all the
>>ingedients as the celadon plus talc, bone ash and black copper oxide
>>instead of red iron, and it seems normal.
>>
>>
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