Tag: tenmoku glaze

Rhyolite and Basalt Glazes

I was beyond excited to work with my newest found material, a rhyolite from Topaz Mountain, in Juab Country, Utah.  This time rather than choosing a handful of very large rock samples (to insure relative material consistency), I instead went to a wash and filled up a 5 gallon bucket with very fine material the size of course sand. My reasoning this time was that consistency is completely relative, and as long as I get materials from the same spots, it doesn’t matter – and I can grab material that has already been 99% processed for me. In the end I think this worked out, because I was able to run 5 gallons of sand through our ball mill with 2x 1 gal. ball mill jars in 10 batches. But I’m getting a bit ahead of myself, because I think it’s important to test fire a material before you go through the trouble of ball milling. So my new first step in dealing with materials (after identification of course) is to take a small chunk, put it in a small dish, and fire to cone 10 in reduction. Since this is my primary temperature range, that’s it, if there are chances I’ll also put similar samples into cone 6 oxidation as well as an oilspot firing schedule, which is about cone 12 oxidation. Here was the result at cone 10, in reduction:

wpid-2015-04-26-17.18.21.jpg.jpeg
A small rhyolite pebble after being fired to cone 10, in reduction.

 

Looks a lot like a fired chunk of granite or feldspar. Onwards with the milling!

Someone asked me about my process for ball milling, and here it is: Fill a 1 gal ball mill jar 1/3 with mixed sized media (approx 50% 1/4″ balls, 25% 1/2″ balls, 25% 1″ balls) then fill the jar with 1/2 gallon of water, then fill the the rest of the container up with material until it’s about 2/3 full.) If I had more containers I wouldn’t exceed filling the jar 1/2 way, but my circumstances are what they are, and I haven’t needed to change anything yet, such as it is.

In reduction, this rhyolite material was surprisingly similar to my ice crackle glaze. I think with very little modification (a small addition of clay, bone ash, and maybe a bit of frit) I’m nearly positive this will look and feel like a Kuan, ice crackle glaze.

Rhyolite Glaze on a high Iron clay body. Fired to cone 10 in Reduction.
Rhyolite Glaze on a high Iron clay body. Fired to cone 10 in Reduction.

Once I had all of my material milled, I let it sit overnight and then drained off the excess water, leaving me with a glaze slurry with an SPG of 1.58 (That’s 79g of material in a 50cc syringe). That’s only important if you want to know how much material you have per given volume. Since I was going to blend this with a basalt material that was also in solution, I needed this info. After taking the SPG of my basalt material, which happened to be 1.54, I did a simple line blend. On both sides are the materials by themselves, in the middle a 50/50, and on the left and right middle 25/75.

wpid-2015-04-26-17.29.08.jpg.jpeg
Rhyolite/Basalt line blend. Red stoneware (top row) and porcelaineous (bottom). Fired to cone 12, oxidation.

 

Pretty interesting results, I think. The big surprise was how sweet the 25% Basalt and 75% Rhyolite mix came out.

1 part Basalt, 3 parts Rhyolite. Fired to cone 12 oxidation.
1 part Basalt, 3 parts Rhyolite. Fired to cone 12 oxidation.

Finally, because I was looking for an oilspot/tenmoku type glaze with this research, I should also detail my firing schedule. Here’s my current Blaauw gas kiln firing schedule:

0 time_temp 00:00 5
1 time_temp 01:30 200
2 time_temp 07:00 1160
3 time_temp 01:30 1200
4 time_temp 01:00 1220
5 time_temp 02:00 1230
6 time_temp 01:15 1252
7 oxidation 80
8 time_temp 00:08 1252
9 oxidation 150
10 time_temp 00:30 1220
11 time_temp 01:30 1200
12 cooling
13 time_temp 02:00 1000
14 time_temp 02:00 800
15 time_temp 02:00 700
16 time_temp 02:00 500
17 time_temp 02:00 300
18 time_temp 02:00 50
19 time_temp 04:00 50

Blaauw kilns have the capability of firing in extremely oxidized conditions – blowing in somewhere to the tune of double the amount of air needed for complete combustion. The default, and maximum air value is 200. An neutral flame is around 100, and a smoky reduction is something like a 70.

Basically, this program fires up to cone 6 in about 9 hours, and then goes slowly up to 1252C, reduces for 8 minutes, and then goes back to oxidation, drops to 1220 over the course of 30 minutes, then drops to 1200 over the course of an hour and a half.  I’m still very much tweaking this schedule, which works very well for some glazes, and not so much for others.

Rainbow Iridescent OilSpot Glazes

Hello Again! It’s been quite some time since my last post. Gotta thank those of you who have contacted me with interest and suggestions! With so many summer projects and school stuff, it’s been very difficult to put my full efforts into any one thing… but life is what happens while you’re making plans.  Anyways, enough with the excuses.

Over the summer I had the time and energy to figure out an acceptable firing schedule in our new Blaauw kilns.  For as much as I love their sleek and sexy design, computer controllers, and top of the line hardware… you can’t look in the damn things while they’re firing. This poses several challenges for control freak oil spotters. Usually, the idea is to firein complete and total oxidation, going slowly through cone 7,8,and 9 to allow thermally reducing iron to bubble up through the glaze and cause the surface to crater or foam. By carefully monitoring the situation inside the kiln, and by pulling out glazed pull rings, the firer can increase the temperature slowly and fire until the glazes have significantly ‘healed over’. This isn’t really an option, so as a result a much more empirical approach was needed to find a good fit.

After 5 firings, I settled on a more or less acceptable firing schedule (the way this programming works is that the kiln starts at 0, take 1:30 to get to 200C, then 2:30 to get to 700C, etc). In Celcius;

time_temp 00:00 5

time_temp 01:30 200

time_temp 02:30 700

time_temp 03:00 1115

time_temp 02:00 1190

time_temp 02:30 1230

time_temp 02:30 1253

cooling

time_temp 02:00 1000

time_temp 02:00 500

time_temp 02:00 300

time_temp 02:00 50

time_temp 04:00 50

 

Once that was established, I began with some of my favorite tiles from my initial 2 rounds of oilspot base glaze recipes. My favorites:

 

NoCo OS:  (NC)

Dolomite 4.4

Whiting 4.4

K200 Feldspar 57.3

EPK 9.7

200m Silica 24.2

Spanish FeOx  10

 

Candace Black:  (CB)

Dolomite          5

Whiting           5

K200 Feldspar 60

EPK                       5

200m Silica  20

Spanish FeOx  8

Cobalt Carb       5

 

Loganspot: (LS)

Local Black Dolomite 10

K200        65

EPK          5

Silica     20

Cobalt      5

Red Iron  8

 

Fake Mashiko: (FM)

K200  37.6

Silica  9

Redart  8

Calcined Redart 35

Wollastonite   5.7

Talc    4.3

Bone Ash  .5

Red Iron   4

 

With these base glazes I began mixing, blending, and layering, and combining glazes with dipped, poured, and sprayed application.  On a whim I decided to experiment with some of my manganese saturate glazes, and that’s when things started to get really interesting. There is admittedly one glaze in particular that I’m not sharing, but with a little diligence and some wet blending, a seriously motivated glaze experimenter can discover this glaze by  looking at my old posting on my OSII series. Blend them all in 50/50 proportions and you’ll get the elusive but beautiful  GF glaze. Hell, it might even be on my blog somewhere. That’s all I’m saying for now – I’d hate to rob anyone of the learning experience… Hah! =)

 

Recently I was contacted by the British potter Allen Richards who has done some pretty extensive research into lustrous gold glazes. He suggested that I try small additions of Vanadium Pentoxide. These glazes feature 2 amended manganese saturate glazes in combinations with the usual oilspot suspects.

 

 

 

 

Here are some videos of some of my latest results. None of these particular tiles have Vanadium pentoxide.  As time goes by I’ll try to annotate the combinations MS corresponds to Manganese Saturate.

 

 

Iridescent Hare’s Fur Tenmoku

Galactic Oil Spot Glazes

An interesting view of my most recent round of test glazes. Each Oil Spot variation was dipped in porcelain and red stoneware  with the red stoneware tiles shown. The firing was: 10 hr oxidation to Cone 7, 2hr oxidation slow climb to Cone 8, 3 hr slow climb to cone 10, 1 hour oxidation hold @ cone 10. The results were pretty cool, and under magnification they had just the right amount of galactic goodness. The pictures were taken with a USB digital microscope! Magnification is about 30-40x

For the longest time I’ve wanted to try firing oil spot glazes, and after a bit of research it was pretty satisfying to make it happen. I decided to begin by concentrating on black, single glaze variations – the recipes of which came from a number of sources, mainly John Britt’s ebook and Complete Guide to High Fire glazes, a few from Michael Bailey’s Oriental Glazes, and a couple from Hopper’s The Ceramic Spectrum. The next step is to start zeroing in on some of the more spectacular variations and then start changing up the recipes and the firing schedules for maximum effect. Enjoy!

What I’ve been up to…

Ice crackle using some of the last of my old stoneware recipe leftover from my move from the Armory.
Ice crackle using some of the last of my old stoneware recipe leftover from my move from the Armory. Not amazing, but not nearly as much trouble getting these glazes to work. The lack of iron in the clay body is what’s keeping the rim from being what I like the most.
More materials.
Local materials. Sandstone, metamorphosed sandstone, quartzite (possible limestone schist), black dolomite, marble, limestone
Materials prospected extremely close to the studio
Materials prospected extremely close to the studio, more prospected glaze material tests. Soda rich mud stone on the back right – it’s gonna make a wicked carbon trap shino.
The  new workspace.
The new workspace. Complete with Insight glaze chem software, which I know understand.,
The clay body tests in Bisque, c6, c10, c10redux, soda, redux cool
The clay body tests in Bisque, c6, c10, c10redux, soda, redux cool. Lots of work, this. What’s not pictured is the hour and hour and hours of firing brand new kilns.
Locally prospected tests.
Locally prospected tests. For those folks still in West Palm, Aplite is the railroad track gravel east of the studio. AWESOME black glaze all by itself.
The are 8 clay bodies with .5 increase and decrease variations of CoTE. Basically cover a range of 4-7, the magic number is still 5.7.
The are 8 clay bodies with .5 increase and decrease variations of CoTE. Basically cover a range of 4-7, the magic number is still 5.7.
12 new clay bodies I'm testing with ice crackle glazes. 3 different firings. The top 7 tiles are new variations of my standard ice crackle with frit and bone ash additions and subtractions.
12 new clay bodies I’m testing with ice crackle glazes. 3 different firings. The top 7 tiles are new variations of my standard ice crackle with frit and bone ash additions and subtractions.
Studio table.
Studio table.
Three cups, same clay, same glaze, completely different firing and cooling regimes.
Three cups, same clay, same glaze, completely different firing and cooling regimes.

Rutile, Ilmenite Variations of 1234 Base

1-10
1-10

Tenmoku Test Tiles – Iron, Rutile, Ilmenite, Earthenware Variants

In an efferot to further explore the different variations of Iron Oxide, Ilmenite, and Rutile – I’ve run a series of tests substituting Red Iron Oxide, for other oxides available in my lab. It was a pretty good series, although on some of the oxides, I overshot the ideal % and on a few I think it could be more.

Notice the 12% addition of Earthenware clays in 8,9, and 10 produce some pretty nice Celadon glazes!

MT Series
MT Series