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Hi there, its good to be able to share. Im Kate and i make my own glazes and im wanting a pink glaze (purple, mauve, lilac etc ok)   I inadvertently used magnesium carbonate instead of manganese dioxide:-

potash feldspar 45

quartz 20

whiting 20

china clay 10

magnesium carbonate 3 (instead of manganese dioxide!!)

pottery crafts say that cobalt carbonate with magnesium = purple  (1-3% = blue?!)

lindathepotter says that rutile has chromium in it and tin oxide added with less clay will give a light pink

spruce crafts say that small amount of cobalt with magnesium will give purple.

so, any ideas anyone on how much cobalt carbonate to put in with my magnesium carbonate??

thanks!

Kate

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4 hours ago, Kate Reeves said:

 

lindathepotter says that rutile has chromium in it and tin oxide added with less clay will give a light pink

 

No chromium in rutile, unless as a trace contaminant.  Titanium (85%) and iron (15%) in rutile.  Chrome tin pinks are mostly what I've used, not familiar with cobalt-magnesium pinks.  You might want to set up line blends with varying amounts of cobalt carbonate to see if you can find a range that works, but I'm thinking it can't be too much cobalt.  My sapphire glaze is pretty intense blue at a bit less than 1% cobalt oxide.

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6 hours ago, Kate Reeves said:

pottery crafts say that cobalt carbonate with magnesium = purple  (1-3% = blue?!)

lindathepotter says that rutile has chromium in it and tin oxide added with less clay will give a light pink

spruce crafts say that small amount of cobalt with magnesium will give purple.

so, any ideas anyone on how much cobalt carbonate to put in with my magnesium carbonate??

- Cobalt will make a purple to purplish to bluish colour with magnesium but the magnesium level needs to be quite high to really get the purple tones. I don't think 3% magnesium carbonate will get it high enough. If you are glaze testing anyways you might as well try it, I'ld try 0.2 up to 0.5 cobalt carb. Just do a progression blend, they are fast.

- Chrome + tin can make pink if the base glaze is very high in calcium. These glazes typically are also on the low side with magnesium and alumina.  For doing test batches a really accurate scale is necessary, especially for the chrome. If you just want a general idea if this base glaze will work then skip the blends and just try 0.20 chrome oxide + 6.0 tin oxide and if you get a red tone you will know if this base supports chrome:tin pinks / reds. If you get pink / red then work on the cobalt to shift the colour.

- I would also try it as is with the manganese dioxide. Pinks can be made with high alumina glazes + manganese. 

- You can get pinks from rutile, with and without tin but it's easier to supply the chrome from chrome oxide rather than the trace amount in rutile. 

- If you do try the chrome / tin be aware that having chrome in the kiln can flash nearby pots containing tin to pink.

- How much of this glaze did you mix up? Is it in liquid form now?

Welcome to the forum :)

 

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Here is a mix percentage for various rutiles you may have use for in the future - no  significant chrome. https://glazy.org/materials/15393
It takes roughly 2.12 parts more Magnesium carbonate to equal 1 part Magnesium Oxide. Magnesium Dioxide is not a typical glaze chemical so I assume you intended to use Magnesium Oxide.  So in your example above you would need approximately  3 g MgCO3 X 2.12 = 6.36 grams of Mag Carb (MgCO3) to equal 3 grams of Mag Oxide (MgO).. Magnesium carbonate does off gas or lose a great deal of its weight (Over half) when heated so it can cause other difficulties in some compositions.

Here are some sample chrome tin recipes that may give you ideas when looking at their chrome and tin composition:

https://glazy.org/recipes/77052
https://glazy.org/recipes/32817
https://glazy.org/recipes/79136

The last recipe has some nice line blend info to show the variations in color vs different alumina levels for that recipe. Chrome tin recipes can be a bit of a challenge. See below line blend.

Cobalt glaze: Mauve / Pink / Lilac here https://glazy.org/recipes/5542

Careful with cobalt oxide and carbonate, same issue. You need just under. 1.5 times more Cobalt carbonate to equal 1 part oxide.

D8253299-4FFC-4576-BBBC-D4224D939C15.jpeg

Edited by Bill Kielb
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  • 3 weeks later...

Neodymium oxide makes a beautiful lilac colour in both transparent and matte opaque glaze bases and erbium a very pink pink (more intense than here in different glaze bases), I’ve got a similar colour to Nd using cobalt , though it was speckled and less pink than neodymium, especially in a matte glaze. https://glazy.org/recipes/84383  or more here https://glazy.org/search?base_type=460&type=830&photo=true

Edited by Ned23
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