Monday, May 17, 2010

Heinz 57 on the Pot

I really wish I could post images from my cell phone directly into my blog. However, I have yet to discover a method. If this were possible, I would post a heck of a lot more often. As it is, I have to e-mail the photos from my phone to myself, ONE AT A TIME (sound of disgust), then go to the hassle of going home, opening my computer, opening my e-mail, saving the images to my hard drive, and then posting them online. What a pain in the tookus.

Anyway, that is why I have only just posted this picture of the glaze that turned out really well on my little bowl. I have mixed up a batch of what I hope turns out to be the same glaze. What I glazed the bowl in was our Heinz 57 mix but from my test tiles, I think this recipe is really really close to the same result:

12.5% neph sy

12.5% Gerstly Borate

37.5% Ravenscrag*

37.5% Magnesium Carb.

2% copper carb

4% iron

*For those of you that don’t know what Ravenscrag is, it is a clay that is produced by Plainsman Clays in Medicine Hat Alberta. It is a clear glaze all by itself when fired to cone 10, and with a little bit of frit, it is a very nice clear at cone 6 (I don’t think you even need very much frit to get it to melt).
What I like about this glaze is the texture. It has a slight pebbleyness to it that forms when the glaze tries to crawl, but then heals over again. It creates a fine pattern of satin and gloss areas, kind of like islands of satin amongst rivers of gloss. This glaze takes stains and oxides well, and this combination of iron and copper creates a toasty warm glaze with iron speckles, but where it gets thicker it has almost a wood ash appearance, in that it takes on a greenish hue and the pebbleyness is accentuated. This tendency for the glaze to crawl can be accentuated even more by bumping up the magnesium just a little bit, and it becomes way more crackly. It still stays somewhat shiny though. This would then only be good for non functional ware, and the outsides of pots (see my test tiles in the previous posts)

The only problem I have with any of these glazes is that the magnesium carb makes the glaze want to start crawling and cracking before you fire it, so as it dries it starts shrinking and forms cracks. This is even more apparent if you dip it over the top of another glaze. It actually curls up and lifts the other glaze off the pot as well.

So, this is either something I have to live with, or try to eliminate. I am just not sure if I will lose the qualities that I LIKE by eliminating the qualities I don’t.

I think I need to add more clay, so perhaps a bit of ball clay, or maybe I just need to back off the mag carb and increase the ravenscrag content. I will have to play around and see what I get.

On another note, I was at the studio on the weekend (what else is new), and I threw some more “pint” glasses. I have been trying to throw a drinking vessel that would hold a thirst quenching quantity of iced tea, water, etc, and to make the shape appealing and elegant, but what I came up with (totally subconsciously) was a pint glass. It looks just like a pint of Guinness (mmmmm.....Guinness....droool). Not sure if they are elegant, but they sure will hold a pint. I also mixed a batch of my new glaze and dipped one pitcher to see how it turns out (fingers crossed), and then I threw a couple of chicken cookers (based on the beer can method, except the beer can is replaced by the ceramic cylinder thrown in the middle of the cooking dish). I will post the chicken cooker as soon as I trim it so you get a better idea

The “pint” glasses, by the way, are all made out of white stoneware, with a clear liner glaze and a blue hares fur on the outside. I have added a spiral sprig to the outside of each glass that I carved out of plaster, and each of those sprigs is dabbed with hot tamale stroke and coat, it looks really good as it melts into and runs down through the hares fur. I will post pics when I have a couple handy. I sold the first 2 that I made at the student sale, and sadly, I did not get any pics of them.

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