Help with Mason Stain 6021

[Dani Montoya]

I love rich, primary colors and i get them successfully though using Mason Stains in a 20x5 glaze base. Wollastonite, FF3134, Silica. EPK and Felspar G200.  They all do beautifully in this base except the MS 6021 Deep Red .  

This glaze, pits and separates and loos ghastly.

I am new to glaze making and know that Reds can be a tad hard to work with. I have discussed this with a local pottery supply place and they dont see anything in my glaze that could cause it to do this. 

So I am reaching out to the community!

What am I using that 6021 does not like and what do you suggest I replace it with. Thanks!!

[Norm Stuart]

I don't have any problem using Mason Stain Dark Red 6088 with glazes.

Looking at Mason Stain literature I can't say how your Mason Stain Dark Red 6021 differs from 6088. They're both zircon encapsulated and list the same colorants.

But we also don't use the "20x5" recipe after a very short trial - because it crawls during our 6 hour slow-cool as shown in this photo.

Instead we use Glossy Base #2 and Calcium Semi-Matte #2 from "Mastering Cone 6 Glazes" or Tony Hansen's Silky Semi-Matte G2934.

Cone 06 low-fire cadmium-sulfide reds, such as the "complete glaze" CM-941 with 11% lead is easily denatured by adding any other ingredient. But I have not experienced problems with high fire reds using Mason 6088.

Buying prepared dry red or orange glaze is much closer in cost to making it yourself, than other glazes where premixed glazes typically sell for 3x the cost of making your own. Laguna Clay as an example obviously has a less costly solution set to red or orange Cone 6 glazes than adding 10% to 15% Mason 6088.  Part of that answer is they use a less costly stain product than Mason.

It seems easy to guess that the chemistry of 20x5 glaze might be corrosive to the zircon coating. But without seeing a photo I'd also suggest that adding 8% to 15% of a refractory Mason Stains, like zircon coated red, is quite a lot of non-melting material for most glazes to take on and retain their fluidity. Contrast this to copper or cobalt which are not only colorants but also fluxes - so adding these colorants makes glazes more fluid.

We use what we call "Tint Bottles" which are 2/3 Gerstley Borate and 1/3 Mason Stain - and double that total weight of water. Although I intended them as an easy way to color base glazes, most people use them by itself, which produces brilliant shiny color at Cone 6 or Cone 06.

5x5 has a far higher silica to alumina ratio and also far more calcium, without magnesium. Which of these differences might cause a problem for Mason 6021, I don't know.  I just know the combinations we use don't cause this problem.

[Arva Traynor]

I would like to use a base glaze and tint with mason stains.  Would 5% mason stain be a good starting point?

[Norm Stuart]

Arva - Unfortunately the percentage of Mason Stain you need to use varies by the color. So tests tiles are in order.

Adding 3% or more zircopax, which costs about $2 per pound can brighten some colors by helping to hide the color of the underlying clay. You'll need to try adding it to a color like black and see if you prefer the fired result with or without the zircopax.

Generally blues, greens and browns require only 3% to 7% of Mason Stain by weight.  These colors are less expensive, typically $13 a pound, and can be replaced with even less costly with copper, cobalt, nickel, iron, and manganese.

Unfortunately a really bright red, orange or yellow will require 10% to 15% of Mason Stain by weight and these colors also happen to be the more costly stains around $25 a pound. Achieving these exact colors with oxides depend on glaze chemistry, and you'll never be able to achieve the same bright yellows or oranges without using stains.