I’m into crystal glazes now ( Tenmoku gold rework)
I knew this day would come. There are only so many possibilities in glaze before you start branching out. Recently I bought a crystal glaze course from the ceramic materials workshop. I was hoping to find out way to make my red crystal glazes better or to get some ideas of new ways to approach crystal glazes I am already frustrated with. Unfortunately the almost 20 week course of content (self guided) concentrates mostly on zinc silicate glazes; Glazes that I am not interested in making whatsoever.
It seems, from my experiments, there is a major misconception about titanium in glazes. While many people claim they are the main ingredient in crystal glazes that cause crystals to grow, it seems that titanium kills off crystal glazes most of the time or in most glazes. Are there glitches out there that rely on titanium?, yes. Is that most of them? I don't think so. The problem is that most crystal glazes are over nucleated which put so many crystals in the glaze that you would assume it’s a matt glaze. There is a good chance that if you have a glaze that you think is a matt glaze when you fire it a little cooler, you have a crystal glaze that didn't melt enough to separate the crystals enough to see them well. Because too much heat will also reduce crystals. But Titanium dioxide, in little amounts, will kill off these crystals just enough to get that separation. This was a major discovery for me (even before the CMW classes) when I was developing my own version of tenmoku gold. The little yellow things crystals would gang up and essentially make a yellow mattish glaze. Look what happens when I added 2% Titanium dioxide.
Newten 7 (7th try)
SG 1.5
Cone 6 ox
Frost porcelain clay
4 second dip
Look at how many yellow spots I'm getting. Over nucleated . Lets look at another one.
Newten 1
Still so many yellow crystals even with a dark back ground.
Newten 6
On the 6th try I upped the metal flux high enough for the glaze to melt. I worried that the glaze was not getting a fully melt. But now I only have crystals in the lower melty part.
So I finally gave in and used 2-3% TIDI because I knew it would kill nucleation of crystals and it worked.
Newten 7 + 3% Titanium dioxide.
3% was just enough to kill off the crystals, making them more visible .
Notes: In almost all crystal glazes I have made the TIDI kills crystals. Allowing them to spread out and grow more or at least making them visually distinct.
Here is my theory. Titanium dioxide does not usually make crystals. In most cases it kills them. But you, the human, can see more crystals when they are more spread out and there are less of them. This visual makes a miss correlation in Matt vs over nucleated making people think the TIDI is the thing that makes the crystals. There is one case (I know of) that Titanium makes crystals. That is titanium crystal glazes. They generally need barium carbonate. I have never made them but I know they exist. I tried once by shoving a large amount of titanium into a glaze but only got calcium crystals.
Matt crystal base +1% black copper oxide
SG: 1.5
Application : 4 second dip
Clay : B-mix with grog
Cone : 6 ox . I already had a semi matt base, the TIDI pushed it in to the Matt region of the stull chart.
Matt crystal glaze + 1% black copper ox
SG: 1.5
Application : 4 second dip
Clay : B-mix with grog
Cone : 6 ox
Viscosity tuning + 4 drops of epsom salt solution per every batch.
Two things. I laid down the theory about Titanium killing crystals most of the time because there are people who think the Titanium MAKES the crystals 100% of the time. I do not think that. Even in the case where I added titanium to a high alumina glaze; I want to make this clear. Most Alkaline earths can make crystals by themselves. This means the crystals are not coming from the Titanium alone, it needs something else. Please keep in mind this is a hypothesis of mine and subject to change. I have correlative tests but nothing that proves this yet.
I know of two people that can make Titanium crystal glazes and they say barium is a necessity. And I Quote “ If I see a titanium crystal glaze that has no barium, it ain’t a titanium crystal glaze” one of them says.
