Layered glazes crawling

[Tumbleweed Pottery]

Hi all... I've been making work in my home studio to a large degree of success, but I've hit a snag recently. I sell these mugs that are horror inspired, so the body of the mug is black (minnesota clay BT 12), and has red drips from Amaco (deep firebrick).

I practice good bisque and glaze hygiene. Always touch bisque with clean hands. Dust off bisque that has been sitting for a while, with a damp sponge. I glaze the inside of my mugs, and leave those for a day to absorb completely. Then I glaze the outside.

Historically, my red drips have worked just fine on my mugs. But recently I've been encountering some crawling where the red goes over the black.

The best I can figure is that I have recently been glazing the inside of the mugs one day, the outside another, and then I come back and paint on the red another day. I'm glazing upwards of 8 mugs at a time, so this method made the most sense time-wise.

Now, I'm thinking that because the outside glaze was dry when I put on the red, it's causing it to crawl. My mentor thinks this may be the case, since the moisture has already been absorbed by the time the red is added. I may need to be brushing on my red as soon as my black glaze hazes over, so the bisque can absorb both glazes' moisture at the same time, and essentially the black and red become "one" glaze.

(Anecdotally, my mentor says that when he's tried to layer glazes over already dried glazes, crawling has been an issue)

Because I sell these with some degree of success, I will be glazing one at a time until I'm sure I've got this right. What do you all think is happening?

[liambesaw]

I think your mentor is probably right.  Some glazes you can apply over dried glazes, but some pull away.

[neilestrick]

I agree. Never let the first coat dry coat dry completely before applying the second coat. 

[Magnolia Mud Research]

11 minutes ago, neilestrick said:

 … Never let the first coat dry coat dry completely before applying the second coat. 

Neil, would spritzing the dried applied glaze surface with water also solve the problem of crawling due to dry under layer?  If you didn't say anything to the second coat, the second coat should not  know it had to crawl. 

LT 

[Bill Kielb]

1 hour ago, Magnolia Mud Research said:

Neil, would spritzing the dried applied glaze surface with water also solve the problem of crawling due to dry under layer?  If you didn't say anything to the second coat, the second coat should not  know it had to crawl. 

LT 

Just a note: often glazes crawl (not always) when cracks develop in them prior to firing and the fired surface tension of the glaze does not allow them to mend back together during the firing. The crack simply widens as the glaze crawls into itself so to speak. Sometimes mending these cracks or micro cracks after application of the glaze works just fine and the pieces fire normally. So you may see folks that just rub them out when noticed and have success in doing that. Layering sometimes encourages the formation of the cracks because of the different shrinkage rates during drying.  Just for the heck of it take a really close look at the dried wares prior to firing, you may discover a simple fix for your current application method. Rewetting may work and may not.

[JohnnyK]

Hey, Tumbleweed... You said you were layering Amaco Red Firebrick over black. Is the black also an AMACO glaze? In Amaco's directions they recommend that you let glazes dry between coats...I have been layering Potters Choice glazes for more than 5 years with great success and have never had a problem with crawling. But then, too, I rarely let a glaze coat dry completely before brushing on the next glaze coat. You might try Red Firebrick over Ancient Jasper for an interesting look. In this case it is applied over a white clay body. Who knows what you would get over a black body.

[neilestrick]

5 hours ago, Magnolia Mud Research said:

Neil, would spritzing the dried applied glaze surface with water also solve the problem of crawling due to dry under layer?  If you didn't say anything to the second coat, the second coat should not  know it had to crawl. 

LT 

Spritzing a dry glaze can sometimes cause it to release its grip on the pot, just like applying another coat of glaze. If you do it a little bit at a time it may work, though.

[Min]

If putting the second glaze on sooner doesn't work there is always magma. A little bit of magma goo mixed into the glaze and layered glazed don't peel. Directions on how to use it etc here. (it's also good for flocculating glazes with low clay content and hardening the dried glaze surface)