Rhubarb Acid tests

One of my students worked with a well-known glaze:

She put it in her fridge with some rhubarb-leftovers and after 2 days it looks white instead of blue. The colorants were leached out.

So I redid this test... and yes it is leaching...  But why? And how?

In this glaze are three colorants: rutile, copper and cobalt.

To figure out or the colorants weaken this glaze I made a triangle to test it:

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I do not renew articles of this website every week but I try to post my latest tests, shapes, works on Instagram. I invite you to follow me:

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