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colored clay/slip casting


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Hi everyone,

Here is a newbie question  :)

I have made cups with porcelain slipcasting. I colored the slip with universal color made for the slip. Now I am in doubt about whether I can place the cups directly on my kiln washed shelves when I bisque fire the cups. Or will they stick to the shelf?

Please help. Thank you. 

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1 hour ago, Fialil ceramic said:

universal color

Could you send a link of what this product is? I can't recall this product being discussed here before. It's probably fine, but just in case it would be good to have more info before saying for sure.

Welcome to the forum. :)

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Hi again, and thank you for welcoming me to the forum :)

I only have a link in danish :), but it is pure powdered color pigment, in this case black. In the description, it says you can color your clay and porcelain slip with the pure color pigment. It is the same as the pigments in this video I found on youtube. Thanks again. 

 

 

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Fellow in the video is using ceramic stains, if your product can be used like this then it sounds like "universal colour" is just the terminology being used in Denmark for stains. I don't know if you are using lowfire or mid or highfire slip, the higher you fire the darker the black should become but depending on what the stain/colour is made from it could increase the fluxing of the slip. Using a cookie (waste thin slab of clay) under the first glaze firing is a good idea like Rockhopper suggested, brush a quick coat of kiln wash on it if you want to be extra safe. In the slight chance it sticks to the cookie having kiln wash on it will prevent this.

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Thank you so much for your replies. Yes it is ceramic stains i have used.  The clay I am using, is porcelain for slip casting in a one-piece mold. First I am going to bisque fire to 980 degrees celcius, and then I will glaze with transparent glaze and fire to 1240 degrees celcius.  I have just made cookies as you both said and will use them to be sure how the slip will react. 

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I don't know how thin you cast your pieces but I found I needed a hotter bisque than 980C  (approx cone 07) or the bisque absorbed too much glaze and it cracked.  This has 8% Mason Best Black stain in the black slip, no glaze on the exterior, glaze fired to cone 6 (approx 1220C). This one doesn't have black stain on the bottom but others I've done with black slip on the bottoms and absolutely no sticking to the kiln shelves (plucking). (I wouldn't recommend not glazing the outside unless you really test them for dunting)

1027796403_DSC_0241(1).jpeg.7250b35b0676db95059375dd4d0e9a66.jpeg

 

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