Cone 6 Blue Hare's Fur Glaze

[jennyd]

Hey everyone. I need some help with a cone 6 Blue Hare's Fur recipe.

 

Nephaline Syenite 47.30

Laguna Borate (Gerstley) 27.00

Silica 20.30

EPK 5.40

100.00

RIO 2.00

Cobalt Oxide 1.00

Rutile 4.00

Bentonite 2.00

 

 

I teach at a community studio in Vernon, BC. Our Blue Hare's Fur recipe was one of our most popular and stable glazes but in the last year or so has been pitting. We have re-mixed and no luck. It is the only glaze that we are having trouble with - all others are fine. Had the same issues with Floating Blue. Members are crying for a blue - what do I do..... Thanks for your help.

[IronMike]

look at this site:

 

http://pottery.about.com/od/glazeproblems/tp/pitting.htm

 

it will give you some starting points!

 

and it may just need to soak at the firing temprature for a little longer.

[Mark C.]

I use a huge amount of rutile glaze and thats a volatile material that loves to cause trouble at any temperature ( I'm at cone 10.5-11)-also the Gerstley borate can cause woes.

this glaze is saturated with colorants (7%) and that alone can cause trouble.

 

The longer soak time will help as the above post noted-This longer soak may also cause some running so be careful.

Mark

[neilestrick]

That recipe is identical to the Floating Blue recipe I have. Try a soak at the end of the firing. Start with 5 minutes. Add 5 minutes as necessary, up to 20 minutes. There are a lot of blues out there that are a lot less fussy than that one.

[jennyd]

That recipe is identical to the Floating Blue recipe I have. Try a soak at the end of the firing. Start with 5 minutes. Add 5 minutes as necessary, up to 20 minutes. There are a lot of blues out there that are a lot less fussy than that one.

 

 

 

Thanks for the tips. I have tried soaking and that did not seem to solve the problem. Do you have a blue recipe that I can test that you would be willing to share. I am, by no means, a glaze expert - following a recipe is pretty much the extent of my knowledge. Thanks for your help.

[jennyd]

I use a huge amount of rutile glaze and thats a volatile material that loves to cause trouble at any temperature ( I'm at cone 10.5-11)-also the Gerstley borate can cause woes.

this glaze is saturated with colorants (7%) and that alone can cause trouble.

 

The longer soak time will help as the above post noted-This longer soak may also cause some running so be careful.

Mark

 

 

I have tried reducing the Rutile to get a more blue look as it was looking rather green at one point. When doing that, should the other colorants be reduced as well? Also, what are the issues with the Gerstley?

 

Thanks so much for your input - I value it all as I am certainly no glaze expert.

[neilestrick]

Gerstley Borate is notorious as the most inconsistent glaze material we potters use. The makeup of the material tends to change every couple of years as they get to different parts of the mine. There have been periods, like for a year or two in the 80's if I remember right, where everyone's glazes went wacky. Gerstley was originally mined for use by the roofing tile industry. No one in the 'fine' ceramics industry (dishes, sinks, toilets, etc) would touch the stuff because it was so inconsistent. Potters like it because it's a cheap source of non-soluble boron, a good flux for mid range glazes. Frits are a more consistent source for boron, but more expensive. I recommend to people that they switch to Gillespie Borate, a frit with the same makeup as Gerstley, so it's a direct substitute. In reality, it'll only cost $4-5 more per 5 gallon batch than Gerstley. It's 100% consistent from batch to batch, and the lack of headaches will make up for the increased cost. That said, it does seem to increase the melt just a bit, so reducing the amount by 2% or so is sometimes necessary. It may help smooth out your floating blue, too.

[jennyd]

Gerstley Borate is notorious as the most inconsistent glaze material we potters use. The makeup of the material tends to change every couple of years as they get to different parts of the mine. There have been periods, like for a year or two in the 80's if I remember right, where everyone's glazes went wacky. Gerstley was originally mined for use by the roofing tile industry. No one in the 'fine' ceramics industry (dishes, sinks, toilets, etc) would touch the stuff because it was so inconsistent. Potters like it because it's a cheap source of non-soluble boron, a good flux for mid range glazes. Frits are a more consistent source for boron, but more expensive. I recommend to people that they switch to Gillespie Borate, a frit with the same makeup as Gerstley, so it's a direct substitute. In reality, it'll only cost $4-5 more per 5 gallon batch than Gerstley. It's 100% consistent from batch to batch, and the lack of headaches will make up for the increased cost. That said, it does seem to increase the melt just a bit, so reducing the amount by 2% or so is sometimes necessary. It may help smooth out your floating blue, too.

 

 

Thanks, I will order a small amount of the Gillespie and give it a test.

[clay lover]

The blues in "Mastering ^6 Glazes" are very dependable, and that book is a great resource for ^6 potters, much info and other stable glazes.