Glaze Test: Surf

I had a new glaze variation in my last kiln firing!

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Not sure exactly where I came across this formula, so apologies for the lack of attribution, but here it is in case anyone else wants to play with it:

Surf
Cone six, opaque matte.

34 nepheline syenite
16 dolomite
7 calcium carb
18 epk
5 zinc oxide

The original recipe says to add 2 bentonite, 0.5 copper carb, and 1 cobalt carb. I’ve never actually seen what that looks like; the pieces up there have 2 bentonite and 1 copper carb, which gives that greenish greyish not-quite turquoise. The only other version I’ve tried had 2 bentonite, 0.5 cobalt, and 1 copper carb, and that gave a very muted, greyish blue that could go very slightly bright sky blue where it pooled.

I discovered it crawls like crazy if you apply it thick with my clear over top, but that’s not unusual. I’ll just slap it on thinner next time.

Sieve

The sieve disappeared from the studio. I need it to mix up some more cephaloglaze. It has been gone for several weeks now.

On the off chance it wouldn’t reappear, I ordered a new one from Pottery Supply House. It got sent to the wrong address. Purolator now knows this, and knows where it should turn up, and if I’m very lucky I’ll have it on Monday.

Monday is the last day in the universe I can have this sieve and still have my things fired in time.

I am a little anxious.

Hmph.

I’ve been trying to upload pics of the Robot mugs and Viking wine cups for a few days, but it’s not letting me. Not sure if it’s a WordPress issue or a myrouterhasanattitudeproblem issue. Will try from a different computer later on today.

Anyway. Colours came out just the way I wanted them to (except for one mug with pink slip, which turned white during firing… time to fiddle with the recipe, methinks), the designs look nice and sharp, and everything is lovely and shiny.

The only downside to this firing is that my big dandelion bowl came out with deep blue fingerprints on one side. Someone (probably me) got cobalt on it, and I’m kinda pissed off about it. Oh well. Someone will pick it up at the Seconds Sale this weekend, and it will be off my hands. At least the colours came out the way they were supposed to, so I know what to do if I make another.

Glaze tests, Round 1

It occured to me I never got around to posting any pics from the glaze chemistry course over the last few weeks. So here’s my first homework assignment: three glazes mixed up based on limit formulas.

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They’re a good illustration of how unpredictable glazes can be, and why potters spend so much time testing them. I was aiming for three light green glazes: one opaque and matte (I got clear satin), and two glossy, semi-clear with fun surface effects (I got one plain glossy clear, and one glossy semi-clear with fun stuff below the surface). And none of them are light green.

They all have the same colourant, 1% copper carbonate. The only difference between two and three is that two contains barium carbonate, and three contains zinc oxide.

As you can see, colour isn’t just determined by your colourants; it’s also heavily influenced by your base. And while some ingredients tend to have certain properties (barium carbonate is supposed to funkify things), those properties only emerge if said ingredient plays well with everything else in the base.

Testing, Testing… 1, 2, 3…

I had some photos for this post, but my card reader’s borked, so I can’t get them onto this computer.

Anyways. I did up two test tiles for the cephalopots, and they’re out of the kiln. I’m using a modified version of a glaze that’s been around the studio for a while… I made my mom a set of dessert bowls two Christmases ago, and that’s what they were glazed with. The bowls have been in near-daily use, and have even been put in the (gasp!) dishwasher for the past six or seven months. The glaze is still perfect, so on top of being nice to work with (easy to get an even coat, doesn’t clump on the bottom of the bucket), it’s sturdy as heck.

The first test tile is the base glaze without any colourants added, and the other has 0,5% red iron oxide. The first came out a very white colour… sort of like the foam on top of a cup of steamed milk. The second is a very pale, creamy beige. The surface texture is matte, and almost feels under-fired, even though I know the kiln hit the right temperature–it’s just the way that base comes out.

I did up a third test tile today. This time, I fiddled a little more with the recipe–brought up the fluxes and brought down the refractories, which means it should melt a little easier, and maybe make a smoother surface. (I don’t know if I *want* it to be smoother. I feel like tentacled pottery should have more texture to it. But I figured I should see if I can make it happen, just for fun, and then decide which texture I like best when i can touch the result, not just imagine it.) I also brought up the iron oxide by another percent, so it’ll come out a wee bit darker.

Should be fired Monday.

“Almost there…” “Stay on target.”

Glazed, wiped and loaded the soap dishes Wednesday night. I was at the studio until 1:00 am, which I did not expect… Glazing takes time, but even after two and a half years making pottery, I can’t seem to wrap my head around that fact. It’s like once a piece has been bisqued, I’m thinking of other projects, the next thing to make. My brain doesn’t want to drag itself back to thinking about those last few steps to complete the object. It’s been off my wheel and out of my hands so long it almost doesn’t feel like mine anymore.

Anyway, the kiln was also loaded with some studio odds and ends, candled overnight Thursday, and fired up Friday. I’ll unload it tomorrow, weather permitting. (We’re supposed to get a storm. I’m half hoping for a day off work, and half hoping it won’t happen at all, because I want this TO BE OVER. Also, someone else has the kiln booked for 4:00, and it would be seriously impolite of me not to unload it before then.)

Last Step

The test soap dish is out. The colour developed *beautifully* where the glaze was thick (and was pretty darn ugly where thin, but that’s okay. The only problem is there was some pinholing–not a major problem in terms of safety, since these aren’t meant to be eaten off of, but it is an aesthetic issue. I’ll be giving up on this glaze and going with the backup, which has less green undertones but no texture problems.

I’ll mix up the batch tonight, and they should be out of the kiln and delivered for payment before the end of the month. Yay!

*sigh*

So, the soap dishes are supposed to have a specific glaze on them. Shannon, who ordered them, asked for an aqua sort of colour; I happened to have some test tiles from about a year previously kicking around, brought them in, and we picked out a combo of the colour in one and the texture in the other.

All well and good, except now that I have the first seventy-five dishes out of the bisque kiln and ready to be glazed, and I want to make up a new test just to be sure I’ve nailed the recipe, I discover I am missing an ingredient. The first one, in fact. (Ferro Frit 3195, for all interested parties.) There was some in the studio when I did the test tile, but sometime between then and now it disappeared/got used up/was taken by fairies.

Cue several hours of frantic researching.

I *think* I can do a straightforward substitute using 3134 instead. The glaze will have lower alumina, but that might actually be a plus… In any case, I can get a tile into the next glaze firing, which will be Friday. If things don’t work out, I’ll just have to order myself a small bag of 3195, and hope it gets here in a reasonable timeframe.