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Painting On 'jet Black Underglaze Stain' To Leatherhard Clay


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I've painted 'Jet Black Underglaze Stain' on to leatherhard clay, just mixed it with water to make a slightly creamy liquid and applied with small brush.

 

I have scratched some away to reveal clay colour underneath (sgraffito).

 

The surface of the underglaze is dry but VERY easily smudges such that I hardly dare touch it now. – is that normal? I am worried!

 

I certainly would not be able to add any other colouur without spoiling what I've done (I guess back should go down last?).

 

Hoping after biscuit firing I'll be able to touch it without it smudging?

 

Then I will put clear glaze over (dipping).

 

Are ready-mixed underglazes (Contem?) less prone to smudging at leatherhard stage?

 

Should I be adding anything as well as water to the stain for leatherhard clay?

 

Any advice very gratefully received!

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I would recommend painting it on sooner next time ... Maybe at what we call cheese hard ... ( Think of a young cheddar ). If the piece has dried hard you could try painting on a thin coat of water first to open up the surface a bit. This could work better than thinning the underglaze. Thinned out underglaze might not give you solid deep colors.

 

After you paint it on let it dry until it is dull, then you might want a second coat. Again wait until it is dull to start on sgraffito.

Smudging is one of the challenges which is why you have to work quickly and make the mark you want the first time. You should be able to clean up smudges a bit when the piece is totally dry.

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I looked up the Jet Black Underglaze Stain since it's not available in my part of the world and the instructions from Bath Potters Supplies in England says to mix it with "universal medium". I'm wondering if there is some gum to help harden the underglaze stain in the medium? I know with the premixed underglazes I use that they dry quite hard and dust/smudge free. Also, since the "universal medium" appears to contain some flux it will help it stay on the pot without becoming too dry when glaze fired as some stains tend to do if used without a flux.

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I would suggest adding something like gerstley borate to it to help it grab the surface and not smudge off. I use gerstley when I mix Mason stains and water to create my hand drawn transfer images. It helps keep the Mason stain together and bind to the surface of the clay. You can also start painting it on when the clay is just firm enough not to show brush strokes and the stain will dry right along with the clay.

 

Just what I do, I would also recommend testing other mediums to get it to bind and find one you like.

 

T

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  • 2 weeks later...

i am surprised you are having this problem. i have never had that issue and i've applied it to both soft leatherhard, bone dry as well as bisque ware. i've actually also applied it as an overglaze and never had a problem. in fact i've applied it over a ^5 fired glaze and done a second cone fire at a lower temperature ^04 and not had a problem.

 

i've never mixed any kind of liquid in it though.

 

i've used a brush as well as bottle needle applicator. 

 

on B mix ^5

 

HOWEVER... whether underglaze or glaze - the powder IS  smudgy after drying (not VERY smudgy but definitely smudgy). i dont handle the direct surface very much - meaning touching the surface of the slip or glaze or underglaze. after i apply it goes on the bisque or glaze shelf and then to the kiln. no extra handling 

 

what kind of clay body are you using?

 

i agree with chris. i would not add any more liquid to jet black. just like she said i'd add it to the greenware. 

 

also i am wondering why you feel the need to wet jet black. maybe instead of a brush you should use a needle applicator. 

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