Sunday, August 16, 2009

clear glaze

On to the less successful products of the last firing!
I have become interested in working with slips. But when I put my clear liner glaze over a piece that had been slipped before the bisque, it became cloudy where thick--as in corners. So I mixed up 3 new 'clear' glazes and fired them over slipped pieces in the last firing. Only one of the four clear glazes gave a really clear cover--Kate the Younger from Lana Wilson's book. The others were cloudy and made the colored slip look pastel--or changed the color completely. The really clear (Kate) was very high gloss and it did the most amazing thing to the slip. I had covered the piece (bowl and platter) with an iron slip--painted on in 3 coats, in 3 different directions. Under 'Kate' the iron slip became bright yellow with dark brown streaks. This striation did not occur with the clear glazes that became cloudy. I guess I am looking for an explanation AND for a clear (^6 electric) glaze that does not go cloudy and reveals the true color of the slip. Any ideas?

These are the glazes that clouded over. There is a stripe of red iron oxide on the right side of test tile.

Here is the test tile for "Kate'.

And here is the bowl:


Anonymous said...

Hello Gay.
I am new to your pages and have really enjoyed reading them.
I have tried many clear glazes and ran into the same problem.
Out of 20 tests I found the best to be a "Non-Zinc" recipe by
Behren Gers Borate 50
EPK 17.5
Flint 32.5
It is a good clear gloss it applied thinly. Fire to cone 5 - 6
I find another commercial one that is super from The Clay Art Center in Washington state called
PZN in gloss or satin. I use this now all the time.
Hope you find this helpful.
A good clear is hard to find.

Sister Creek Potter said...

Thanks, Shar. I will try it. I plan to mix up several other clear glazes that have been suggested and see If I can find MY favorite clear. I also plan to thin them out more--I may have my glazes too thick.

Ron said...

Here is a good cone 6 clear.
Spodumene 25
F-4 Feldspar 25
Silica 25
Gerstley Borate 25

You can add oxides for color too if you want to use it over a white slip.

Amber add 4-6% Black iron oxide
Creme add 2% Black iron oxide
Green add 3-4% copper carbonate
Blue add ?? cobalt carb

White Slip Cone 6 (use on leather hard )
Neph Sy 27
EPK 16
OM4 17
Silica 33
Borax 5
Bentonite 2

Run some small batch tests of these to see how they work for you. They were in regular use at Clayworks.

Sister Creek Potter said...

Thanks, Ron. I'll run some tests tomorrow--well, I'll mix up the glazes tomorrow--but I've got to get some bisque work for the tests--so it will be a bit of a while for a report!

Ron said...

Gay, If you don't have black iron oxide you can use red iron oxide with similar results.

rox said...

Gay, I can see that this clear glaze search has been a long and hard road.

Do let me know if you remember to what you find and I will try to remember to come back here to see your results.... but we do have a hard time remembering with all the things filling our lives, AND CUTTING INTO OUR CLAY TIME! I am a part owner of a shop downtown that is fair trade and a gallery. Then I saw your husband had surgery: Mine has leukemia and is doing his third treatment in fifteen years. He is taking two kinds of chemo for the next year!

And if that were not enought to fill my time: I am a retired public school teacher with credentials and background in English, art and special education that can not stop working with kids. So I tutor and sub and love it!

Off to get ready for a fun day with some former students: WILL TIE DYE for just plain fun! In 100 degree heat!

Linda Starr said...

and I thought when I made my 35 test tiles each of three different cone 5/6 clays I made too many - Ha I can see I'll need all those and more, I hope you find a good clear; I'll be keeping an eye out and my fingers crossed.

chaetoons said...

Mornin' Gay
Don't have a clear glaze recipe to offer (would if i had one!)
Want to say -- your bowl is gorgeous !!!

StonewareGlazes said...

I have a high-fire clear over at my site:

Check it out.