[Clayart] Glaze has changed its features

David Woof via Clayart clayart at lists.clayartworld.com
Wed Oct 28 20:31:32 EDT 2015


Hi Judy, hi John,
John makes a vital point re what surprises can accumulate in the bottom of the bucket.  Under certain conditions, with age, and chemical interaction with other materials, borates can precipitate out and form heavy crystals that swirl around in the bottom muck of the bucket, largely un-noticed and in this state is of no further value in the glaze.   Also I think Dannon mentioned the preponderance of Neph Syn. and Ghastley Borate in that recipe and I too think it is a red flag that you could do well by re formulating or seeking a different glaze.   As I'm sure you know new can bring new life to our life and our work.

Misneach,

David Woof


----------------------------------------
> Date: Wed, 28 Oct 2015 06:01:30 -0400
> To: judylee947 at yahoo.com; clayart at lists.clayartworld.com
> Subject: Re: [Clayart] Glaze has changed its features
> From: clayart at lists.clayartworld.com
>
> Hi Judy,
>
> Most problems I have seen like this are caused by incomplete mixing between batches. You say you are using a paint mitxer to redisperse, but are you really getting every last bit of sludge off the bottom of your storage container? Put your hand down to the bottom and see what is there. If you even leave a tiny bit the composition will begin to change over time because that sludge is not the same composition as the glaze recipe. The longer you keep a glaze the more likely this is to happen—it definitely is not evaporation of some glaze component. The changes will be gradual so you won’t notice at first, but after 12 months and multiple uses?????
>
> This is why I have long recommended that you actually pour the glaze out through a sieve when you get ready to use it again. This will let you see what is left on the bottom, scrape it out, and add it back to the glaze slop.
>
> Although I am just guessing, I would say you will not be able to recover this glaze to its original content.
>
> Regards,
>
> John
>
> Ain’t no thought more vexin’
> —or more dad-gummed perplexin’
> Than the question I’m about to you reveal
>
> An dat’s—
> How do de potter put de handle on de pitcher
> Whilst the pitcher be-a-spinnin’ on de wheel?
>
> Johnny Hart (B.C.) 2003
>
>
>
>> On Oct 27, 2015, at 7:55 PM, Judy Lee via Clayart  wrote:
>>
>> I have been using a glaze from Michael Bailey's book Glazes Cone 6. It is
>> called GA 23, Satin Matt base. I use the light green recipe for GA 23, but
>> have made all three colors (rusty bronze, light blue-green, and light
>> green). The book indicates the glaze was developed by Val Cushing and Pam
>> Fredericks. Since I use this glaze for many things, including large urns
>> and platters, I mixed it in a large storage bin and keep it on a moving
>> dolly to roll it in and out from under my worktable. Lately it has not been
>> working like it used to and the color is coming out more gray in places. I
>> mix well with a paint mixer each time and a stir stick with each dip, but it
>> seems to have a 'carbon trap gray' in splotches when fired. I mixed a huge
>> amount about 12 months ago and am still using it. Could something be
>> dissipating/evaporating from the glaze? I hate to throw out the whole
>> batch, and don't know if I can add something to bring it back...before I
>> make a brand new batch.
>>
>>
>> Recipe for GA 23 Satin Matt, cone 6-7 - by Val Cushing and Pam Fredericks
>>
>>
>>
>> Neph Syenite 41.8
>>
>> Gerstley Borate 10.4
>>
>> EPK Kaolin 12.5
>>
>> Whiting 10.4
>>
>> Lithium carbonate 6.2
>>
>> Flint or quartz 12.5
>>
>> Titanium dioxide 6.2
>>
>> 100.0
>>
>>
>>
>> +1.0%-2.0% copper carb for light greet
>>
>> 1.0% cobalt oxide for light blue-green
>>
>> 3.0% red iron oxide for rusty bronze
>>
>>
>>
>> Advice would be gladly received.
>>
>>
>>
>> --Judy Lee
>>
>> 408-306-0338 cell
>>
>>
>>
>>
>>
>> MAILMAN_MIMEDEFANG WRAP
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>>
>> MAILMAN_MIMEDEFANG
>
> MAILMAN_MIMEDEFANG WRAP
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