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Mason stain troubleshooting


Cendre
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Hello all.  I recently started experimenting with mixing Mason stains in with my b-mix clay body.  The green I tried came out beautifully, but the crimson when fired to cone 6 was left with no color.  Any suggestions?  I thought maybe I hadn't done a high enough percentage, but after doubling the amount it still was the same amount of  colorless.   I just did a small pebble of clay and left one side unglazed and covered the other with Mayco's zinc free clear and that didn't keep the color in either.

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18 minutes ago, Cendre said:

Hello all.  I recently started experimenting with mixing Mason stains in with my b-mix clay body.  The green I tried came out beautifully, but the crimson when fired to cone 6 was left with no color.  Any suggestions?  I thought maybe I hadn't done a high enough percentage, but after doubling the amount it still was the same amount of  colorless.   I just did a small pebble of clay and left one side unglazed and covered the other with Mayco's zinc free clear and that didn't keep the color in either.

Not all colors remain at all temperatures. Have you made yourself a color key of your colors fired to cone 6 to see which fade and which don’t?

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22 hours ago, liambesaw said:

For crimson it specifically says no zinc and:

  1. Glaze must contain 6.7 to 8.4% CaO (12-15% CaCO3)

That includes "clay body" or slip

Sorry for my ignorance, does this mean that my clear glaze must have the CaO  in it to hold the crimson color in the clay body? Is this something that can be added? 

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3 minutes ago, Cendre said:

Sorry for my ignorance, does this mean that my clear glaze must have the CaO  in it to hold the crimson color in the clay body? Is this something that can be added? 

It means you need to add some whiting or wollastonite to your clay body.  And it also means make sure any glaze you use doesn't contain zinc.

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5 minutes ago, Cendre said:

Sorry for my ignorance, does this mean that my clear glaze must have the CaO  in it to hold the crimson color in the clay body? Is this something that can be added? 

You can look at the reference table there and choose a cadmium red that has the code 1 in it, 1 means it can be used as a body stain.

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45 minutes ago, Cendre said:

does this mean that my clear glaze must have the CaO  in it to hold the crimson color in the clay body? Is this something that can be added?

I wouldn't be adding calcium carbonate (or wollastonite which contains silica plus calcium) to an existing claybody. Calcium is a flux so if you add it to an already balanced claybody it's going to be over fluxed and you will have issues with overfiring. The cadmium inclusion stains that Liam mentioned don't need a specific minimum amount of calcium (or any at all) in the claybody or the glaze. Cadmium inclusion stains are very pricey and there are some warnings regarding their use. No grinding / ball milling of slip, clay or glazes containing it and if the items are for functional pots then consider getting them tested for cadmium leaching. Is using a red stained slip or underglaze overtop of your claybody an option for what you are doing? It would be far less expensive than using red stain to colour the claybody.

Edited by Min
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12 minutes ago, Min said:

Is using a red stained slip or underglaze overtop of your claybody an option for what you are doing? It would be far less expensive than using red stain to colour the claybody.

I had been using underglaze which works great but had wanted to try a colored clay body to reduce a step in the process and get a little more precision. Ive been making very tiny roses and so the amount of clay actually needed is quite minimal.  

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3 hours ago, Cendre said:

I had been using underglaze which works great but had wanted to try a colored clay body to reduce a step in the process and get a little more precision. Ive been making very tiny roses and so the amount of clay actually needed is quite minimal.  

Sounds like the Mason 6088, 6097 or 6021 might be worth testing for colouring the clay.

3 hours ago, liambesaw said:

BTW I have tried deep crimson and crimson in a glaze and it came out green despite having no zinc and 10% CaO

How much magnesium was in the glaze? Did you try increasing the CaO to 15%? and have the alumina on the low side?

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18 minutes ago, Min said:

Sounds like the Mason 6088, 6097 or 6021 might be worth testing for colouring the clay.

How much magnesium was in the glaze? Did you try increasing the CaO to 15%? and have the alumina on the low side?

It was Hansen 20x5, which is supposed to be a good base for chrome tin reds (which the crimsons are) but I didn't invest a whole lot into that effort because I only bought sample sizes of those mason stains.  Was trying to steer away from cadmium.  Ended up just using a chrome tin pink glaze instead.

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