Glaze Worth Mentioning

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If you are working in the 2020°F glaze firing range, this glaze works well. It strongly resembles a "floating blue". The color is much more saturated and a richer blue than my photo shows.

It's a high Gloss where applied thick and doesn't run. Oxidized, electric firing.

Base Glaze:

52.5 Frit 3124

14.7 Silica

9 EPK

3 Lithium

7.6 Zinc

7.8 Cornwall Stone

5.4 Whiting

Plus:

2 Tin Oxide

2 Lithium (that's in addition to the 3 in the base glaze)

1/2 Cobalt Oxide

Note: i measure by parts. And use 1/8th tsp as a base measurement. Thus: 1/2 cobalt oxide would be: 1/2 of 1/8th tsp. Plus: i halved the above base recipe but didn't half the additives: tin, lithium and cobalt oxide.

I was seeking a pink. Spozedly lithium and cobalt oxide will produce a pink. But this didn't.

Still -- am quite pleased with the "floating blue". It's a keeper.

On the inside: Where applied thin, it's a steelish blue; the areas where 2+ coats were applied are the sections it "floated". Plus, (on the outside) where applied over a yucky chocolate brown glaze, it covered it well but the double-glaze is nothing to write home about.

Firing schedule:

200°F to 300°F

324°F to 1300°F

Full heat to 2000°F

Hold: 15 minutes

Full heat to 2020°F

Hold: 20 minutes

Full ramp speed drop to 900°F

Hold: 40 minutes

Explanation: the only reason the hold is between the 2000°F and the 2020°F, is because my Paragon kiln doesn't operate as it should and shuts itself off !!! Thus, i added an un-needed hold in order to coax it to reach 2020°F and this seems to work for this kiln. If i were firing a normal kiln, i would fire at full heat straight thru from the 1300 to the 2020°F. However, if my kiln operated correctly, i would be firing to Cone 6 !!! instead of recomputing all my glazes to the lower temp.

Chae

Fiddlin' Around

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Have recently been teaching clay classes.

Decided that having a theme would move the classes along in a somewhat orderly progression.

Chose musical instruments.

Had already started this banjo as a model for the first class, when i realized, much to my dismay, that it surpassed the abilities of the enrolled age group.

So!

Have spent the last couple of weeks remodifying my game plan.

We're still doing musical instruments.

Just on a drastically more basic level.

Still, without the motivation of teaching classes, it would never have occurred to me to try and create a banjo !!!

The tuning pins were a bit of a logistics problem. But think i have this solved.

The next challenge is: how in the world to i prop this upright in the kiln? If it warps a'tall, i'll be in the soup.

Have a day or two to figure this out while the clay dries before bisque firing . . . .

Am just a'hopin and a'prayin that it survives both the bisque and glaze firings, and then, actually makes music !!!

Chae

Old Discovery Made Anew

Even the smallest amount of Dolomite will turn a glaze matte !!!

As y'all know, i've been trying to modify all my glazes to vitrify at 2020°F.
Soooo
Drew up a list of materials and oxide melting points. Dolomite's melting point is 1472°F. Now, silica's MP is on the high end of the scale at 3110°F. I was hoping that in the language of eutectics, the Dolomite would lower the melting point of the silica. Or some such thing. Actually, computed the formula a little more precisely than that.
But it's Dolomite that is the culprit here.
All 6 of the new glazes worked. But darn if they're not ugly.
An' didn't i use Dolomite in every one of them. To help bring the glaze melting point down, of course.

But even the smallest amount of Dolomite will turn a glaze surface matte . . . .
7.7 out of a 100 percent isn't very much, you know.
But just for future reference
If you want a glossy glaze
7.7% is too much.
It will give a Satin Matte glaze at best. Otherwise, just a plain ole stoney matte.
Chae

Trying to Understand Glazes and Gas Kilns

What can i tell you? That i don't understand gas kilns? Yep. That would be a true statement. Am i sorta getting a handle on it? Perhaps . . . .

Yesterday fired these pots under the assumption, that while i've never been able to get the Olympic Torchbearer 1827G to reach temps of 2167°F, it has consistently heated beyond temps of 2012°F. Since, both the electric and gas kilns seem to be in cahoots with each other, i've been trying to modify my cone 5-6 glazes to accomodate the kilns.

OK. Here's the scoop. Arranged the shelves in the kiln totally differently than previous attempts. Used 2 half shelves placed 3.5 inches from the bottom. Put 2 more half shelves on 10-inch posts and balanced them on the first set. Put the 4 bowls on these shelves. Then, balanced a full shelf on more 10-inch posts which placed it 4.5-inches from the top.

The air-intake valves were approximately 1/8th-inch from the closed position. The draft at the top was covered to approx. 1/3rd of the opening.

The first peephole would have been measuring heat of pots on the bottom half shelves (if any had been placed there). The second peephole measured the heat of the middle set of half shelves, and the third peephole measured the heat in the space above the top shelf. One should probably pay attention to these type of details before they fire a load. Me? I arranged the shelves and the pots. The hour was midnight and did i mention that i was already exhausted? Yesterday morning at 6am, as i fired the kiln, wondered why the pyrometer was giving me three different sets of readings: top peephole read 2150°F, middle read 2050°F, bottom read 2000°F. Which one of the three i should be paying attention to !!!

This morning, after removing the bowls, i measured both the shelf spaces and the peephole openings. An ounce of precalculation is worth a pound of cure, they say. But i lucked out.

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I should mention here, if you're gonna try out new glaze recipes, try not to concoct them when you're positively exhausted and your mind is laboring to overcome a dull, throbbing headache. It's not that you can't build a perfectly wonderful glaze computation which turns out swell and nicely vitrified !!! It's that after you have done so and fired them, you find you've forgotten to meticulously write down the ingredients in a logical and repeatable order!

So! To the best of my dead- (tired) reckoning, here is a recipe that will vitrify at temps between 2020°F and 2050°F:

Neph Sye = 10

Frit 3110 = 50

Bone Ash = 5.5

Magnesium = 3.1

Dolomite = 7.7

Lithium = 5.5

EPK = 5

Silica = 7

Talc = 6

xxxxxxxxxxxxxx The outside of this bowl has the above recipe (base) with 4 parts Zinc added. Let's call this: (#A). It's a satiny matte.

The inside glaze is a combination of the above recipe (base) with (#B) which has 4 parts Rutile and 1 part Red Iron Oxide added. Then, an additional overlay of the glaze (#A) with the zinc was added. It's super glossy and quite attractive in its own way.

Now . . . here comes the part about inadequate notes. A few days ago, fired a recipe high in manganese content trying to produce a lustre glaze. Fired 3 different bowls with 3 different amounts of manganese on the inside with different glazes on the outside. One had antimony; one had potassium dichromate. While all the glazes vitrified at 2020°F in the electric kiln (oxidation), they were not pretty. Dull matte surfaces. No lustre.

Naturally, i thought - well - they needed a reduction atmosphere. Put them in yesterday's firing. Since they were formulated for temps of 1999°F to 2020°F, most of the glaze surfaces boiled at 2050°F. Some did not, which is confusing in and of itself !!! But it's the color we're interested in here.

Note: On the bottom bowl: the potassium dichromate turned a putrid green in reduction. Not cool when in theory it was spozed to be an orangy-red.

The top bowl with the antimony on the outside turned ugly shades of gray sprinkled with white.

However !!!

The inside of this bowl which had been a dull metallic gray and originally glazed with:

Manganese = 36

Gerstley = 32

Lead Bisilicate = 20

Frit 3110 = 4

Red Art = 4

With the addition of Glaze recipe #A ( 4 parts Zinc) liberally brushed over the pre-fired surface and fired in reduction, turned glossy with rich red-highlighted tenmoku coloring !!!

This isn't the greatest picture of it; the one above shows the richness of color and glossiness better.

So! There you have it. Such as they are, notes on firing gas kilns and metallic lustres which didn't luster and cone 03 to cone 1 glazes which did vitrify, amidst notes on overlaying glazes.

If you're not ready to throw in the towel by now, stay with me. More notes on experimental glazes to follow when formulated and fired !!!

Chae

Steve Graber Tool

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ok. So ok. This is a little rough and the lid needs attention but it's my first effort at working with Steve Graber's tool which arrived via U.P.S. delivery a few days ago.
Am tickled with the tool. It creates all kinds of potential new design ideas.
Chae

Imagination Needed Here

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Discovered this morning that i really don't know how to photograph "shiny gold" effectively. Placed these pieces here. Placed them there. Placed them everywhere.

Still

The light sparkled off the gold; overexposing some areas, darkening the rest of the gold areas to reflect a "brown" rather than the shimmering gold.

Soooo

Imagination is needed here. Can you see the bright golden lusters resting luxuriously upon sunset colored sands?

When held in the hand, these pieces boast of far off magical lands awash with shimmering gold in the last orbs of the day.

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Chae

Results

OK !!! I feel a little more positive now.
It's as if, after much searching thru the convoluted maze of pathways at the world's fair, i finally found the cotton candy booth. Oughta mention here: i love cotton candy!

Here's the scoop.

About three-quarters of the way thru yesterday's firing, realized i was trying to do two opposing things simultaneously.

1.) Was still working under the theory, that with different programming, i could get the little electric Paragon to reach a mid-range temp.

2.) That i had concocted glazes for a much lower temperature range, and if brought up to 2142°F quite possibly, they would "boil" and the effects of the whole firing would give misleading results.

Opted for the lower temperature range. Specifically 2016°F with a 15-minute hold.

Used 3 different glaze calculations.

Here are the results:

Glaze 1 xxxxxxxxxxxxxxxxxxxx Glaze 2

Both glaze 1 and 2 vitrified. Glaze 2 is richer, more glossy and a much better glaze. In both cases, i poured glaze into the bowl, swished it around, then poured the remaining out. Glaze#2 is a Conrad G170, cone 3-5 gloss. It worked well, but if used again, will apply 2 coats for i think that will give better results. The pea-green color resulted from the basic glaze with 1% copper carb and 0.25% Rutile added. The dark purplish blue had 0.5 cobalt oxide and 0.25 magnesium added to basic glaze.

Neither of these glazes ran at all.

ok.

Now for the prize. This next one is a glaze formulation which i found on the internet which had been published in Ceramics Monthly's April 1998 issue. Notes on the glaze mentioned that it had a Cone 1-6 range but sometimes bubbled at Cone 6.

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It is a rich creamy glossy turquoise glaze. Perfect. Only needs one coat. But 2 coats wouldn't hurt it. Doesn't run at 2016°F temp with a 15-min hold. Will definately use this formulation again.

Name: Wrights Water Blue

Cone: 1-6 Oxidation

3% Lithium Carbonate

9% Strontium Carbonate

59% Frit 3110

12% EPK

17% Silica

Plus:

2% Bentonite

5% Copper Carbonate

Wasn't sure the clay i am using would vitrify at this low of a temperature either, or that the glaze would marry the clay. It's Georgies G-mix 6 with grog. It has a stated range of cone 4-6. However, the clay is extremely versatile and i've used it before when doing raku firing. Had noted, then, that the pieces with a raku 80/20 glaze would hold water indefinately without the liquid seeping out. No leakage.

If sound counts for anything a'tall, a fingernail pinged against the side of the bowl gives a lovely melodic sound as if the clay has vitrified !!!

Currently, have water in all three bowls checking for seepage or leaking.

So !!!!

There you have it. There may be a way around dysfunctional kilns.

After a year in the doldrums, a wee bit of my lifelong positive attitude is returning! And i am soooo glad to meet and greet it again . . . .

Chae