How Matt is Real matt
I wanted to do a one off test of my recent red glazes. Knowing that Ancient copper is a red crystal type Matt glaze I first need a Matt base, Something orange if not reddish. In previous tests I thought Ancient Copper was essentially a red crystal glaze. I was wrong. It’s a matt glaze for sure. The Matt being produced by an alkaline earth such as Mg0. Semi matt or matt? I don’t know. But it is near the crystal side of the stull chart. So I put together a high alumina, low silica base with plenty of flux. It ended up being in the part of the stull chat where Matt lives just to see how low I need alumina and silica to create the iron and/or Mg0 crystals. By the way, I think people think of crystals only in terms of the large zinc bursts they see on Instagram and the like but technically alumina is a crystal and so are other minerals. When Alumina develops in a glaze matrix it spreads into little crystal that when together create that coating many of us call a Matt glaze. TLDR matt glazes are just a coat of little crystal alumina together. When you have a glaze with a good amount of alumina and it develops with proper heat you get a Matt glaze. It’s more complicated than that but in a nutshell that’s what's going on. I wanted to see how far I could push Alumina with some color enhancers like zinc. I did a small line test with titanium dioxide and zinc. Here were the results.
p.s All tiles are on b-mix with grog fired at cone 6 ox and double dipped on the top most layer. This means the top portion of every test is always a thicker application. I do this for all of my tests.
If you want the recipe to these tests I have posted them publicly on my glazy profile. Here is the link: https://glazy.org/recipes/480278
The majority of these tests have a base recipe (posted on glaze) and modified with things like titanium diox and zinc to see the effect, Almost all of these glazes fall on thee semi Matt portion of the stull chart.
Where this glaze falls on the stull chart.
Revamp #2 base: Base test. The amount of red is fine but I need it a bit lighter. This is too deep red, almost brown.
Revamp #2 base glaze + 1% titanium diox. The addition of TIDI usually makes things a bit lighter. ( I have a TIDI addiction)
Revamp test + 3% titanium diox. Just made it more Matt.
Revamp test #2 + 3% titanium diox + 3% zinc ox
This is where is gets interesting. See the color under the Matt surface? The zinc is having a great effect.
Ultimately these tests were nothing but a side adventure to see how Matt I can get a base while keeping the red color I am used to. Next test we will increase the silica by 2, lower the epk a little bit and add back the iron. I understand that Ancient copper is a Matt glaze but I do not think it’s so deep in the Matt portion of the stull chart. At the moment I'm leaning towards no Titanium Dioxide while slowly adding zinc to a semi Matt base. The real test will be when I find the perfect Matt red base to do a zinc line test one. 3% all the way up to 20%. I’m also invested in testing the difference between Red Iron Oxide and Black iron oxide as the Black iron seems to be a more pure colorant, but I have no tests to prove that at the moment.
