Wednesday, 25 August 2010

Need some advice from experienced potters please!

I finally finished the two vases I was coiling and I'm very happy with them. Here they are:


These are made with white stoneware, and I had originally planned to slip inlay a couple of my Jane Austen designs and just glaze them clear. But now I'm thinking how lovely these would look with one of Mayco's Crystalite glazes. The problem is that those glazes are for earthenware...

...bear with me now while I think out loud...

I know a bisque firing would normally be between 955c and 1060c, bearing in mind that the more the clay matures the less absorbent it will be for glazing... yeah, I'm thinking I might have just answered my own question...

Reader: What question?
Me: Yeah, I talk in riddles in person as well.

...Well, usually with stoneware you would (obviously) glaze fire at a higher temperature than the bisque fire, but with low fire glazes on earthenware it's the other way round because the clay won't mature at the low temperature required for the glazing. But the glazes adhere to the surface because... they have something in them to make them sticky (apparently). So... and here's the question...

I'm wondering if low fire glazes are sticky enough to glaze stoneware if the piece is fired at a stoneware temperature first??

You see, I don't want the piece to be under fired, and previously I have used low fire glazes on stoneware that wasn't matured and the glaze cracked on the inside. (I know, I know, that's why there are high fire glazes specifically for stoneware!) But the low fire glazes are so pretty... and I can't coil with earthenware. You see my dilema.

I'm thinking that if I go ahead with this plan it's just going to be an experiment isn't it?

Breaking news: Inspiration struck at about 4am! Update to follow!

5 comments:

Kathy L said...

NO advice Linda..Sorry...But you know I love your work.
k

createniks said...

We only work in earthenware so no help here, but those are lovely.

createniks said...

Correction we bought some bisque porcelain from an art sale years ago and glazed them with 06 glaze and they fired beautifully.

Kim Hines said...

actually reading a few blogs tonight. you could test the idea on a small test piece, but i'm thinking it won't work. the piece will be vitrified if you fire it to stoneware temps and the glaze will roll off when you try to apply it. there's ways around that, but the fit of the glaze will likely be wrong and you'll end up w/ bald spots or funky areas after you fire it (my technical lingo astounds me sometimes). if you want to test the idea out, make a small bowl or something, not a flat tile. you want to see how the glaze acts on a vertical surface. good luck!

Undaunted said...

Thank you so much Kathy! :)

Scott, that's good to hear. I did a little reading on the internet myself last night and it seems many people have good results glazing this way. I decided not to risk it in the end with these particular pots, but it's something I will keep in mind for other pieces.

Kim, that's exactly what I was worried about about - bald spots or drips on my shelves! Also, crazing on the inside again. I don't know why, but it only ever happened on the inside. I thought a way to avoid that could be to glaze the inside with a high fire glaze and then use the pretty low fire just on the outside. I'm going to try it, but not on these ones.

Scott and Kim, thank you both so much for your advice. As I said, I've decided not to try it on these particular pieces. Inspiration struck really late last night! Update to follow!