A discussion by Jonathan Kaplan on dealing the with fickle nature of this glaze
The following is a submission from Jonathan Kaplan email@example.com to the Clayart discussion group on the Internet.
I've been a participant on this list for probably 5 years or so, and it amazes me that for this length of time, there are many re-occurring topics, not to mention perhaps the most popular one, "RE: Floating Blue." And of course, there are many others, too numerous to mention, but its the nature of the list, and that's OK. But I am troubled with the threads on "Floating Blue" and I'll tell you why.
Seems to me that this is a fickle glaze, to say the least, fires in the neighborhood of cone 6 oxidation and when it works, gives a blue with some interesting surface activity, sometimes called a "reactive" glaze. Also,it's apparent to me that this glaze gives a reduction type surface in an electric kiln, which we all really know fires in a neutral atmosphere. What is most obvious to me in reflecting back on years of this post, including some of Ron's adjustments that when it works, it works fine, which is not very often, and when it doesn't work, it has been called many nasty things, one of the most recent calling it snot green. Whatever. And my sense is that it doesn't work most of the time at least in the comments that I have read on the list. So I am prompted to ask why are you struggling with this glaze, loosing pots over and over in a valiant struggle to obtain this surface? Sure I know that many are not able to have a gas kiln, and that's fine. But to continue to butt heads with this glaze seems to me counter productive, to say the least. So what to do? I'm hearing it now, "God, I really want that funky runny surface active glaze with lots going on in my electric kiln but this Floating Blue is driving me nuts." "And here's Jonathan putting in his 2 cents." Or something like that.
Let me propose the following suggestions. I preface this by including here that as a custom production shop for the ceramics industry including the pottery, giftware, tabletop, etc. segments of this field, we work throughout the temperature spectrum and in any atmosphere. Let me postulate that a surface reminiscent of "Floating Blue" is very obtainable without the struggle of using "Floating Blue" at mid range temperatures in an electric kiln. We do it weekly for clients. While I am not at liberty to post formulas that would violate my non disclosure agreements with my clients, here are some ways to achieve this "elusive" surface.
1. Layering glazes. To develop surface depth and activity, layer glazes either by dipping, pouring, or spraying. Of course, you have run many tests before committing a large body of work, haven't you?
2. Use a slip glaze underneath your glaze to develop a breaking surface, or use a slip glaze over your glaze. We have used a glaze that is mostly Barnard slip with some additions over a one of our glazes to produce a fabulous variegated surface with incredible depth (and yes, blue or blue grey/green) at cone 4 in the electric kilns.
3. Combine two glazes in a line blend. Trust me, some of our most successful surfaces have resulted from this simple task.
4. Use commercial glazes for your temperature range over your shop glazes for either a full coating or for decoration.
5. Diversify the fluxes in your formula. We use several base glazes at cone 5-6 that contain Fusion frits as well as spars.
6. Take a glaze that fires at a higher temperature and re-calculate it to fire at your temperature.
7. Combine some or all of the above suggestions, and of course, test test test.
8. And finally, eliminate "Floating Blue" as you may know it, from your glaze repertoire, and concentrate on not trying to duplicate the reduction look in an electric kiln. Use and exploit the electric kiln for its virtues and incredible firing
To expand somewhat on Mr. Kaplans comments we could offer the following pointers:
Since Gerstley Borate is no longer available this whole issue may seem to be a moot point. However Floating Blue works well with Boraq, a Gerstley Borate substitute that you can find out more about at www.gerstleyborate.com. The availability of this material has fostered the study of Gerstley Borate and the whole idea of a plastic borate. It seems we did not appreciate this material while we had it. For more information visit https://digitalfire.com/gerstleyborate/recipes/floatingblue.shtml.
Out Bound Links
A classic recipe from David Shaner. It is a brilliant highly variegated blue.
2004-03-12 - This glaze has its own page at www.gerstleyborate.com This is a good example of a glaze that works well using Boraq 2 as a substitute for Gerstley Bo...
By Tony Hansen