Monday, April 11, 2011

Bring On the Tests...


So I've been working out some new ideas and need the glazes to make the pieces work. Given the excessive problems my pug mill has created, I have LOTS of seconds sitting on my bisque shelf. I always hang on to things that don't make it through the first firing - blow outs, cracks, serious warpage. These become great pieces for testing glazes and i have plenty for this round of testing. Based on the images in my sketch book, I've decided to just apply the glazes to these test pieces to give me a better idea of what I'm trying to achieve, rather than dipping tiles.

All of the tests are to go with my finicky slate matte glaze which I am far to stubborn to give up.

First the crackle recipe from my last post: I have a soft pink that I'm interested in working with which contains 10% erbium oxide, and need some other colors to compliment it. I tried some tests with a deep crimson stain and a blackberry wine stain, both from mason. Both came out mostly gray, with streaks of both burgundy and green. Incidentally, I also had an older batch of glaze I was testing the blackberry wine stain in that was specifically for use with red stains and even though it's not a crackle, I decided to throw it on some pots anyways.

I was also interested in working with some blues and greens in this crackle base but decided to leave those for now.

Okay. Wait. That's not entirely true. I tried a couple of tests: dark, rich blues from a combination of cobalt and manganese. But that led me to the realization that I need to spend some time in the paint department of my local hardware store to study blues together, since I intend on using the crackle blues with my sky blue glossy glaze.

For the green tests, I tried some praseodymium oxide in amounts of 7% and 10%. The 7% came out very soft, while the 10% pushed the glaze to a matte. Not quite what I'm after. I don't think.

As for the matte glazes I tested, I can tell you that a base with zinc does NOT like encapsulated stains. Gave me a very interesting frothing effect. Could be good on sculpture, but definitely not on dessert bowls. And the barium matte glaze did not give me the brights I was looking for either. The colors were way too soft.

I also tried out some black. I tried black underglaze both under, and in the crackle glaze, and another version of the same underglaze that I saturated with copper oxide for a metallic look. I also tried using the Licorice glaze from the Mastering Cone 6 book. This bucket had been sitting around for about 8 years. Just needed some water and a good sieving and it was ready to go.

So have a look. Here's what came out:

This first piece used the Licorice where I wanted the black. Clearly it didn't work so well, blended too well with the surrounding glazes. And see that froth? Interesting, no? Ummmm. Yeah. Not quite. You can also see the green/gray that was supposed to be a burgundy color. It's nice, but not what I'm after just now.

And then there's this piece:

So this piece is actually starting to go somewhere. The darker pink stripe is the blackberry wine glaze I mentioned earlier. The black pinstripes are black underglaze. The darker stripe is a  moss base glaze with about 5% blackberry wine in it. I had this bucket sitting around from tests I was doing a while ago. Again, I just decided to throw it on, since I had it around. I'm glad I did this because I think the colors all work well. The Arabesque lines are a black underglaze that I loaded up with copper. The results are actually quite metallic, but you can't really see from the photos.

So where to go next? Well, first a look at what I don't like about this piece. I feel like the decoration is more "stuck on" the side of the pot, rather than a part of it. I don't like that. Maybe some carving? I'm not sure but I'll work on it. So back to the testing and we'll see where things go!


  1. Manganese is very toxic with far greater activity by inhalation (like the dust found in every glaze room in the world), manganese can cause a poisoning syndrome in mammals, with neurological damage which is sometimes irreversible. Thia chemical is a very poor studio mate!!! Hilary

  2. Erbium oxide is a very unpleasant chemically and should not come in contact with skin or respiratory tract, almost unavoidable in the studio setting.

  3. Could you discuss your liner glaze tests that keep food surfaces seperate from decorative surfaces. Also, discussion of the studio clean up needed after working with a known neurotoxin like manganese. A lot of people who read helpful blogs like yours are new to the craft and may not have any idea of the personal safety aspects of choosing to work with certain chemicals that can be ordered online without questions or warnings. thank you in advance.

  4. Hi Hilary;
    Good point! I'd be happy to devote a post to safety issues.
    As for Manganese, I am very aware of its toxicity and handle and fire it accordingly. I may reserve comment on this chemical until I am writing more about its use in any glazes I am testing.
    As for Erbium, the health information I have access to is here:
    Please feel free to add more links to any information you have.

  5. Now, on to your question about the liner glaze. I am using Ron Roy's Clear Glossy Liner, from the Mastering Cone 6 Glazes book. I chose this glaze because it has been extensively tested by the authors of the book and found to be safe for use with food. While I haven't specifically mentioned it, you can see that this glaze is used on all surfaces that come into contact with food. As I mentioned in my previous post, I will devote a post to safety issues, so please stay tuned!