Need help stabilizing glaze: Leach 1234

[Haywire_Hakaze]

I'm a student at Henderson State University working with some fairly stable glazes in the college's studio (stable as in, not much crawling), and Leach 1234 is one of them. It is our standard "white" glaze. It's a great glaze, except it tends to make glaze-less bubbles along the rim. I hesitate to call it crawling, since it's minor, but it's not at all pleasing.

At first, it was thought to be a problem with user error, when it came to applying the glaze,,, but that isn't the case, as tests have shown, so.... All I can think of is the recipe.



Leach 1234

Custer Feldspar 40
Silica 30
Whiting 20
Kaolin 10
----------------------
Zircopax 10



My professor thinks it might be an issue with the silica content so he wants me to experiment with the quantity in the glaze. I plan to do that, but I figured I would look into other solutions. Anyone have a clue what could be causing this?

[Andy Clift]

I am surprised no one has chimed in on this yet, maybe everyone is on their way to NCECA. Could you explain

glaze-less bubbles along the rim

in more detail.

[Haywire_Hakaze]

I thought I uploaded pictures in my original post. Sorry about that. Here's an example of what I mean. The cup above is Satin Black over Leach 1234 and as you can see, most of the cup came out fine. But just at the rim, there's a tiny bit of crawling (but it's small enough that I just say it bubbled up a bit). It's the only area of the cup that does this, so we're trying to figure out the problem. No one wants their lips touching a sloppy rim that feels funny.

It's a great glaze, but there's that little crawling issue.

[Andy Clift]

Try a small test batch using distilled water. Also what temperature to you bisque fire to?

[Andy Clift]

Hey there,
I am not sure how long you have known about this resource, but it has been around for about 10 years and has just received a MAJOR facelift. Something new I would like to emphasize is that when there is a discussion about a specific glaze recipe, that you also submit it to the glaze recipe database located here Clay & Glaze Recipes

Thanks for your post and please get the word out to fellow students!

[gwynneth]

Hi, if you look at Lili Krakowski's reply on clayart, I think she has it right- too much opacifier.

Also you might try lightly fettling any drips/bubbles on the pot before you fire it, these can also give problems, especially on rims.

I regularly use this glaze with various additions in both oxidized and reduced firings.