"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).

A Minor Victory, But Sweet None-the-less

Problems in ceramics tend not to surface until your full-on into production. Case in point: my slate matte glaze.

I love this glaze. I hung onto if for a year, working out how to use it in my work. When my glossy sky-blue glaze struck a chord with the slate matte, it was full steam ahead. Or so I thought. Most pieces were fine. Made it from start to finish with no problems. But anything taller, with straight-ish sides was a whole different ball of wax. I was losing anywhere from 50 to 95% of these pieces in each kiln load.
That's a lot of garbage to be making, and honestly, I can't afford to make trash.

The problem? Large pinholes, or what looks like blisters in the glaze that had popped, the edges healed, but the center remained bare clay. On the smaller of these pieces, like my tall cups, there would be one or two of these blisters. Enough to ruin the piece. Larger pieces, like my large vases, would be covered. COVERED in these blisters. Not a pretty site.

So where to begin?

There's any number of reasons why a glaze would do this, so I just started moving down the checklist trying to figure out what the hell was happening.

Perhaps some organics left in the bisque were causing the problems, but a higher bisque didn't help. Still got blisters.
Moving on, perhaps it was gases swirling in the kiln? I checked my kiln vent, adjusted it accordingly but that didn't seem to help either.

Okay.....

Next thought: water vapour. Thinking wet glazes were casuing problems, I let them dry before loading my kiln.
Nope. that didn't work either.

Okay. Maybe it's from overfiring the glaze? It only seemed to happen on these taller pieces, which also occupy the top shelf of my kiln. Cones indicated my kiln was firing evenly so I tried going from cone 6 down to cone 5. Boy did that ever make the glaze ugly and flat. And the blisters persisted.

With firing things ruled out, I moved on to the glaze recipe iteself. Was there something in there that could be causing this? I sent copies of it off to trusted glaze experts, but they didn't notice anything out of the ordinary. The EPK was a bit high, in the crawling range, but I wasn't experiencing any crawling, and even substituting some calcined kaolin for the some of the epk didn't solve my blister problem.

At this point I was beginning to believe it was an application problem. And I'm not set up for spraying glazes, so that wasn't even an option.

I moved on to glaze additives. First up was some CMC gum. Perhaps the glaze was drying too fast on the ware?
Nope. That didn't help and just made things messy.
Ugh.
Next was some Darvan and sodium silicate. I thought, what the hell, but that didn't work either.

Now it's important to point out that by this time, my husband just cringed whenever it was time for me to open the kiln. It's hard making work when you have orders and deadlines, and you have to throw most of it away. Many kiln openings were accompanied with cursing and/or tears. But I'm stubborn and I persisted.

Chatting with a fellow potter at a show, I asked him if he added anything to his bucket of matte glaze. The answer? Epsom salts. The same epsom salts that ruined my clay body. I tsp per 10kg batch of glaze.
And bloody hell, if it didn't work like a charm!

Epsom Salts, or magnesium sulfate, is a flocculant. These help prevent glazes from settling, which I didn't think my glaze needed since it had so much clay in it. But apparently they also help with glazes used for dipping or pouring. I had come to believe that air bubbles were being trapped against the surface of my bisqued pot when I dipped it, and that they couldn't escape until the glaze was melted. But being a matte, the glaze didn't flow enough to heal the surface like a glossy glaze would. The epsom salts create a porous surface in the raw glaze so perhaps its easier for those air bubbles to escape before the glaze melts?

At any rate, I guess there's a couple of lessons I take away here.
- Don't put out a line of pottery to my wholesale clients until I have worked with it thoroughly first, to try and spot any problems.
-Ask for help. I have no problems with this. Many times I'll get answers that I have already tried, but there's bound to be someone, somewhere, who's done something I haven't thought of.
- and most importantly, never give up! If you want to solve those problems, you have to keep plugging away at them. Now, it's better to do this if you don't have the pressure of HAVING to get things done by a certain date (see the first point) but perserverence pays off!

Testin' Time Again...

Well, it's the time of year for me to break out all my glaze ingredients and go to town testing, testing, testing!

I recently unloaded 10 cubic feet of glaze tests and ...

Wait for it ...

not a single one gave me what I was looking for!

Glaze testing can be a colossal pain in the ass. I'm not going to lie. But it's a necessary evil. Before I fired this kiln load, I only had a vague idea of what I was looking for. Sort of...

I want another pair of colours to compliment my new line of work. Something simple, and earthy. Maybe a bit "warmer" than the slate gray and ice blue I'm currently working with.

 I had ideas in my head for a kind of warm, wheat colour in my matte glaze, and a nice, toasty merlot colour for my glossy liner. The paint chips here show the colour of matte glaze I am after in the center. It's called "Desert Fortress". (Am I the only one that thinks that's a pretty bizarre name for a colour?) But I digress...The merlot colour is shown on the right.

Since my ice blue is a stain, I thought 'what the hell' and got mason's 6006 to try after seeing some AMAZING results with it from a collegue of mine.

After that last firing, I can assure you that I have no interest in pursuing the 6006 stain. I used this base glaze, which meets all the requirements for a chrome/tin stain (CaO in 12 to 15%, zinc free) but alas, I was disappointed.I want to maintain a somewhat translucent glaze which can be tricky with stains, especially since this one has tin in it. To keep the translucence, I need the stain in percentages of 3 to 4%. Unfortunately, it was too low to give good colour. But any more than that, and I loose the depth and end up with very commercial looking, flat, opaque colours. Oh well...

Then there were the results for my matte glaze. I was using iron, nickel, rutile, titanium, and even tin and copper in various blends to get the wheaty colour I was searching for but to no avail. Most of the tests came out pretty ugly. I got lots of orange-y browns, fleshy colours but not that beautiful shade of "Desert Fortress".

 if you are interested in any of these colours, let me know, I'm happy to share...

There was however, some good news in all of this testing. I didn't get to see all of my results until after a visit I had with an incredibly talented potter, Iris Dorton. We had a long chat about all things pottery when I went to visit her in her fabulous new studio. She has a stunning new line of work and I was picking her brain on how she made this transition. She was quick to point out that her new line of work uses the same colours and compliments her old line of work. This should have been obvious. My new colours and forms are such a HUGE departure from my arabesque collection that I had no idea how to tie the two lines together.


After this visit, and then unloading my kiln to see all these tests, it finally came together. I am going to bring my purpley-blue glaze over to the new collection of work for my glossy liner, and work on the wheat colour I'm after for the matte glaze.
 
 Seeing all of my test results, I can extrapolate and have a much better understanding of the blends necessary to get the colour I'm after.
 So some fine tuning and I'm confident I can get what I want. And I think the two colours will not only look smashing together, but will help to bring the two lines of work together. So stay tuned for some more testing....

More Feltware

Here are some of the latest additions to my feltware collection. I'm feeling pretty confident about the process now and have a system that is working really well for the templates I'm using for this type of 3D felting.

I'm especially enjoying playing with the colours available to me with the wool roving that I am using for the felt. And my slate glaze has become a perfect neutral to pair it with.

As usual, it's my limited time to play that I find the most frustrating. But I have been adding a few 'extra' balls of clay to my daily 'to throw' pile and this means making a few pieces a week to felt. While I would love to focus MORE of my time on this new venture, it's just not going to happen. I've got orders to make, bills to pay, and shows to get ready for. So, while my pace may feel glacial, at least it's moving forward.