[Clayart] Glaze has changed its features

Paul Gerhold via Clayart clayart at lists.clayartworld.com
Thu Oct 29 08:14:20 EDT 2015


Judy,
One of the problems with very large batches of glaze is that solubility of ingredients can become a problem over time.  If you have been adding water to maintain the glaze consistency you have been gradually lowering the soluble components in the glaze.  Gerstley and lithium are both somewhat soluble and could be a problem.  

I would try taking a small amount of the glaze, weigh it and then try adding lithium carb in small increments to see if the glaze is salvageable.  

The Gerstley is also soluble to some degree but I don't use the stuff so if it is the problem maybe someone else might have a fix.

Paul

Sent from my iPad

> On Oct 27, 2015, at 10:46 PM, Rand O'Brien via Clayart <clayart at lists.clayartworld.com> wrote:
> 
> Judy,
> You might check whether the recipe was for "old" real Gerstley Borate, or the new fritted Laguana GB.  I have found major differences in some glazes.  Others, not so much.
> Peace,
> Rand O'Brien
> PearTree Pottery
> Dover, NH
> 
> -----Original Message-----
> From: Clayart [mailto:clayart-bounces at lists.clayartworld.com] On Behalf Of Judy Lee via Clayart
> Sent: Tuesday, October 27, 2015 7:56 PM
> To: clayart at lists.clayartworld.com
> Subject: [Clayart] Glaze has changed its features
> 
> 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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