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Underglaze pencil smudging/running


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I’m drawing with underglaze pencil on green ware mugs I’ve slipcast. Then I take the bisqueware and add more pencil as well as some watered down underglaze for a painterly effect. I’m dipping in clear glaze and firing to 1200. But the underglaze is running/ smudging downwards when fired. please can someone advise as I don’t find that much on the web. 

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13 hours ago, Magnolia Mud Research said:

I solved a similar problem by a re-bisque firing before dipping in clear glaze.  The water in the glaze was the cause of the bleeding of the underglaze applied to the bisqued surface.  The bleeding was not visible until after the firing.  The second bisque “set” the underglaze.   

LT

Not necessarily. All of my underglazes go through bisque before glazing, but my glaze moves enough to make them bleed a bit (which I do on purpose). If I stiffen up my glaze, they won't bleed.

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14 hours ago, Magnolia Mud Research said:

I solved a similar problem by a re-bisque firing before dipping in clear glaze.  The water in the glaze was the cause of the bleeding of the underglaze applied to the bisqued surface.  The bleeding was not visible until after the firing.  The second bisque “set” the underglaze.   

LT

So maybe to save work I should bisque mugs, then draw and paint in one just need to be careful not to smudge, then re - bisque and then dip clear and glaze high fire. 

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2 hours ago, Love rose ceramics said:

Will try that. Thank you. I’m using a dipping glaze so I’ll remove some water 

To make a stiffer glaze that doesn't move (and pull the underglaze with it) the recipe of the glaze needs to change, not the amount of water used to mix it up. It needs to stiffen up so it's not as fluid, adding alumina is the usual way to do this, kaolin (epk should work) is a good source of alumina and is in many glazes already. Are you using a commercial glaze or mixing your own?  For 100 grams of dry glaze you could try adding 2 grams of epk, mix it up and dip a test tile with your underglaze pencil on it (either on bisqued on or not). Add another 2 grams of epk and repeat with another test tile. Keep doing this until you've added 10 grams of epk. If you are using bottled wet glaze then do the same thing but weigh out the liquid so you can replicate the results, I'ld start with 150 grams of wet glaze. If necessary silica can be added also but I'ld try it just with epk first.

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