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Ruth Reese

Making Underglazes (Or Stains...) Run Under A Cone 6 Clear

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Hi All,

 

I'm not a very technical...   However, I often see painted underglazes or stains under a clear which makes them (the underglazes/stains) run and its all very juicy and messy!  It's not so overwhelming that the design doesn't come through but theres a fluidity that's exciting.  Can anyone suggest a set of relationships that might do this?  I'm working at cone 6 usually porcelain. I've been looking at Julie Galloways recipes but it's all a little unclear to me.   (No pun intended :)  I'm happy to use commercial glaze arrangements or make my own :)  Thanks! 

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I fire at cone 10 in a gas reduction kiln, so keep that in mind.  Stoneware and porcelain are my clay bodies.
 
If I use underglaze on a pot and bisque fire the pot after applying the underglaze, there is usually no bleeding of the underglaze at the edges.  Depending on the composition of the glaze applied over the underglaze, there may be some 'dissolving' of the underglaze into the clear glaze.  If that happens, I change to another clear or quit using that underglaze / glaze composition. 
 
If I apply underglaze to a bisqued pot and do not rebisque the pot, the application of a glaze over the underglaze usually causes bleeding.  It is due to the water in the glaze moving the 'stuff' in the underglaze during application, especially if the over coat is applied by dipping, pouring, or brushing.  If spraying is done very carefully to avoid excessive 'wet' spots,  the bleeding can be avoided. 
 
Some underglaze colors do tend to be 'dissolved' into glazes applied over them.  It is due to the glaze being a solvent for the colorant in the underglaze. 

 

If my underglaze / cover glaze combination consistently bleeds I design my decoration to allow the bleeding; i.e. I depend on the bleeding to be a part of the design.
 
LT

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The fluidity of the clear glaze will have a lot to do with it. If the clear is stiff and doesn't flow, then the underglaze won't flow. You can basically take any clear and increase the flow by increasing the fluxes. If you're working at cone 6, adding Gillespie Borate would be a good start, in 3% increments until you get the flow you want.

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Yeah, I'm the proclaimed "Underglaze Queen" of the forum (Paul's fault! :D ), and here is my experience with wanting a more "watercolorey" effect with your underglaze.

 

When I was first starting out, I worked in midrange uderglazing. For me, the glazes tended to bleed and run the most when I added too much clear glaze over them. It was wholly accidental on my part--rookie error, haha. But, if you like that effect, make some standing test tiles and muck about with the layering of clear. :) Also, adding gerstley borate as a flux to your underglazes should up the bleed factor a bit, too, especially with Mason Stains. Play around with the ratios until you get the desired effect. :)

 

I work in lowfire sculpture instead of throwing now (easier on my poor creaky body), but underglazing is still my primary surface treatment. ♥

 

-Guinea

 

P.S. I almost forgot; watering down the underglaze and splotching it on with a small sponge or brush makes for nice effects, too. :) Feel free to visit my gallery if you'd like to see some of my watercolorey technique. I have lotsa animal portrait stuff in there that relied on my underglazes blending smoothly, especially the brown lop rabbits.

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If you're ok with commercial glazes, I've had some good results with Spectrum's Satin Clear ^5, taking it to ^6.  But there is a fine line, I've noticed- it over fires really easily and gets bubbly, yet if you only go to ^5 the underglazes won't get runny!  It might be worth experimenting with though.

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