how to make underglaze bleed & run

[levialaska]

Hi all, 

Wondering if anyone has recommendations on how to achieve a bleeding and running effect with underglazes. I've included a few pictures where the blue (I'm assuming underglaze) is showing the effects I am trying to achieve: the bleeding edges shown on the plate with blue circle, the bleeding/minimal run on lip of goblet, and the running on the bottom cup. I've been trying it with Amaco underglaze on bisqued pieces followed by Amaco transparent and fired to both cone 5 as well as 6. I have also tried applying it on top of the transparent, but every time the edges stay pretty crisp. I'm fairly new to ceramics as a hobby and would love any tips or insights anyone has! Thanks so much for your time!

Best, 

Levi

 

 

 

 

 

 

[Rae Reich]

Are you certain that those are underglazes? Looks like cobalt oxide or cobalt saturated glaze applied over the base glaze. In that case, runniness will very much depend on the runniness of the base glaze. 

[levialaska]

Thanks for the reply Rae! I will give that a try. I've tried to apply cobalt oxide to bisque and then follow with clear, but it always smeared and got everywhere. Perhaps applying overtop of the clear glaze is the answer. Thanks!

[Benzine]

If I were trying to make an underglaze bleed, I'd thin it with water and/ or apply it to a wet surface so it would be more likely to diffuse.

[Tamas]

In my (limited) experience natural oxides like cobalt or copper tend to bleed more than commercial underglazes, also if the clear glaze has a tendency to move in firing that will blur the underglaze - for example this glaze here:

 

Soft Clear

[neilestrick]

If your glaze is fluid, it will pick up the underglaze and bleed it. Some folks say it is more likely to bleed if you apply the underglaze to bisque, but I haven't found that to be true. I apply all of my underglazes on leather hard, then bisque fire before glazing, and my underglazes bleed just fine.

[preeta]

I am curious why you want to use an underglaze. Bleed and run are quality of glazes.  Why can’t you use glazes like Stroke and Coat instead. It’s colours are kinda like underglazes.  Though not all the colours go to cone 6. 

I don’t know much about commercial glazes to give you suggestions. 

If you can test a lot overfire a clear to make the underglaze run the way you would like.  However running is gravity so it will only happen on vertical walls.  On flat surfaces as others have pointed out the thick clear will turn smokey white. 

[yappystudent]

Mayco has a product called Pottery Cascade, a type of glaze that you layer under, over, etc: your other glazes. I've the clear and white versions of it. I've tested the white and it does make underglazes run. I'm about to fire a test with the clear but don't quite have a kiln load yet. The clear is supposed to be by far the runniest. If for some reason you continue to have problems you might try and pick some of that stuff up.