Thursday, June 6, 2013

"Fun" With Those F*%&ing Stains

So several years ago while I was developing my "Slate" glaze, I was playing around with some other colours for my matte glaze as well. At the time, I tried a commercial stain called "Blackberry Wine" in my base glaze. I thought it was lovely but not quite what I was looking for at the time.

I added a bit of another stain called "Pansy Purple" to push the colour away from burgundy and more towards a dark wine colour. While the colour was exceptional, I lost all of my matte-ness, and shiny was definitely not the look I was after. (The photo doesn't really do the colour any justice, but here it is:)

 As usual, life got in the way and the colour tests got pushed to the back burner. The test tiles went into my huge box with 11 years worth of other test tiles and there it sat collecting dust until recently.

I am still interested in an eggplant coloured matte glaze for my Classic Collection and decided recently to revisit my Blackberry Wine stain. I mixed up a quick sample, based on that very first test as a starting point and was all excited.

Until I opened my kiln.

The colour had all but drained from my glaze and I was left with this rather anemic looking ugly gray. Certainly NOT what I was after.

Now let me explain a wee bit for those not so technically knowledgeable regarding the finer points of glaze chemistry: the stain that I am using to get the original colour uses chrome and tin. These are fickle fiends and require very specific glaze chemistry to pull off their colour magic - no zinc, fire under 1260'C, no magnesium in the glaze and lots of calcium. Check, check, check, and check for the matte glaze that I am currently using.

So what the fuck happened to my colour?!?

An excellent question and one which I have no answer to.

At first I thought maybe I could juggle the calcium in the glaze a bit - perhaps there was TOO MUCH so I bumped it down to the optimal range.

As you can see, the colour got even worse. At least the last time I was getting some speckles of wine colour. This time, nothing but an ugly, flat field of gray.

So I thought I could try adding some other stains to help boost the colour, like that Pansy Purple I tried before:

Or a Deep Crimson:

Better. But not the colour I'm after.

I even tried the Pansy again in a greater concentration:

While it's sorta lovely, there's still too much speckle there for my tastes and the amount of stain required to get this is horrendously high (16%).

So where does that leave me?
I have no flippin' idea.

I am currently at a loss as to why this particular glaze is behaving the way it is, and why it's changing SO FREAKING MUCH from test to test. I'm wondering if there's just too much kaolin in the glaze for the stains to truly come out? Except that I have a stone matte glaze with 5% Blackberry Wine in it and the colour shows up just fine. Or maybe there has been some sort of change to the ingredients that are in the base glaze that I am unaware of? Something coming from a new mine, with slightly different composition? After all, it makes no sense that a glaze that worked fine not three years ago is a complete disaster now. If anyone has any thoughts on this, feel free to post comments. I'm always open to insights.

In the mean time, I'll continue trying to get the colour I'm after. I'm presently trying a new base glaze so we'll see. These things never go as planned, and always seem to take waaaaaaay longer than I'd like. But so it is (sigh).