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Benzine

Staining a Clay Body, for Marbled Clay

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I was looking to stain a white clay body, with a couple different stains, and was wondering if there would be any concerns, I might not be considering.  I was looking to usong Mason Stain 6300  Yellow and 6485 Mazerine.

Any precautions, beyond the basic, I need to take, when using either of these?  Will either affect the clay body, in a way that would cause defects?  Will the colors remain true, with a clear glaze over top?

I've workes with stains before, but usually just red or black iron, so there is a lot I don't know.

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Chris Campbell is still the queen of coloured clay! She makes some percentage range recommendations on her website for a few colours, including the Mazarine one you mention.

http://ccpottery.com/colored-clay-lessons--chris/how-to-color-clay-with.html

She uses an old Hobart mixer to blend her stains in and she describes her process, but I think if you had a little time and space you could mix stain into slip with a drill mixer and dry it like reclaim.

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Marbled being the key word---

first run some blend tests.  3-5-7% of stain: find your color. Chris Campbell is a good resource as mentioned.

step 2  (requires some estimating). Slurry the white clay into a  paste ( slightly thicker than honey) with the color blend you decide upon.

the fun part- slab roll your clay down to tile thickness 3/8". Use a 1 or 2 or 3" paint brush ( brush size = color vein size.)  paint a strip of yellow down the length, leave a blank stripe, then your other color, blank space, then yellow, blank, then color, etc. etc.

fold over evenly, repeat process, fold again, repeat process, final fold. Send through a final time under slight compression to remove air.

caution- fold over slowly so you do not trap air between folds.  Second caution: the more you wedge- the more the color will blend.

EX. Less wedge = more color definition and marbling.  More wedging = color blending and loss of definition.

T

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Mason 6300 Mazerine is a cobalt/zinc silicate stain and Mason 6485 is a titanium/chrome/antimony stain, since the stains have different bases they might not combine in an expected way, like watercolour paints do. Also, since there is chrome in the 6485, and chrome is very refractory, it might make a difference with the covering glaze being a bit "dry". Covering glaze can contain zinc for the Mazerine but Mason doesn't give info for the 6485 Yellow but in glazes chrome plus zinc tends to make brownish colours. 

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18 hours ago, Benzine said:

The piece I plan to make, with these stains, is decorative, but could they be used for something functional, with a clear glaze?

Definite maybe. If it's a well balanced clear glaze fired to maturity then it's more likely to be okay but the only way to know for sure is to have it tested. Could do your own home tests for acid and alkaline to rule out a non-durable glaze but they don't rule in a glaze as non-leaching.

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19 hours ago, Min said:

Definite maybe. If it's a well balanced clear glaze fired to maturity then it's more likely to be okay but the only way to know for sure is to have it tested. Could do your own home tests for acid and alkaline to rule out a non-durable glaze but they don't rule in a glaze as non-leaching.

They clear glaze is my standard, commercially made clear.  To be clear (Pun not intentional, but not avoided either) I wasn't planning to mix the stain with the clear, to color it, just put the clear, over the marbled, colored clay body.  I wasn't sure if any of the stain, from the clay body, could combine with the clear, and leach out. 

Last year, I made a couple mugs, where I stained my clay body with black iron oxide, and marbled it with the normal clay body.  I just put a clear on those.  I wasn't worried about leaching, because neither my wife, nor I, have hemochromatosis.  I haven't noted any change in those, with near constant use.  I was just slightly concerned with a pigment that is more toxic than iron.

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Since stains are in effect fritted colourants (with some additions) they are going to be safer to use than raw oxides or carbonates to produce the same colours. Not knowing if your commercial glaze is well balanced is adding another variable to your question.  Correct me if I'm wrong but I seem to recall that you fire at lowfire temps? Since crazing can be more of an issue with lowfired clay and porous claybodies there is another variable. How much chrome or one of the other materials would leach into the glaze from an unbalanced or underfired glaze or from craze lines or porous clay? I don't know. I don't think there is a definite yes or no answer to your question. 

 

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Dang it Min, I want definite answers!!!  Since text doesn't convey sarcasm or joking, I will note, that I am joking...

I appreciate your responses.  I think I'll just make the mugs, and give them some tests, before use.  I don't plan to sell them, or really even make more.  I just had some extra of this marble batch, from the main decorative piece I am making. 

You are correct, I am currently doing low fire, until my home kiln gets hooked up.  The commercial clear I use is great.  It is forgiving enough, that even student work, has had almost zero issues.  I've only had it craze once, and that was when I tried to do another marbling experiment, with two *different* clay bodies.  It was delayed crazing too.  Apparently the fit  is great for my low fire white, but not whatever the low fire red, that was left from a previous instructor...

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