Here are a couple of sets I made using concrete as a glaze material. It was pretty simple to make. The project began after finding two concrete paving tiles in a construction rubble dump. The larger one I kept for the bases, and the other I busted with a sledge hammer into gravel sized chunks. The gravel went into a bisque kiln, and the remaining slab went into the brick saw to get cut in half. Once the calcined concrete came out of the bisque, the friable powder went into the ball mill and ran for a relatively short 8 hours. After sieving out the remaining sand and large pebbles, I had myself a pretty nice looking glaze slurry. Overnight I noticed a lot of settling, I added a small bit of epsom salt, and what I guessed to be about 1-5% by weight of bentonite. It still settled a bit, but not so much that you couldn’t use it. The application of the glaze was dipping, with a bit of spraying to build a thicker layer of glaze on the top half of each piece.
Derek Au, who runs the incredible open-source glaze website Glazy.org has some great videos out on youtube. In this video Derek gives a super simple and straightforward walk through of using volumetric blending to create test glazes.
If you’re not familiar with Derek, or Glazy, I highly recommend you check him out!
Friend and fellow Oilspot fanatic Leonard Smith has put together some great videos on Chinese glazes. I’d highly recommend checking out his Youtube Channel and taking a look. This one shows a Chinese potter reduction cooling for iridescent oilspots!
More local Basalt. Here used as colorant in high fire celadon glazes. On the top left, the raw material which was collected from various places throughout Idaho and Utah (and all mixed together), bottom left the homogenous, calcined, milled, sieved, and dried material ready for glaze.
In this set the basalt is supplying the iron necessary for that timeless celadon blue. Its also bringing significant additions of magnesium and calcium to the recipe. The % of basalt here ranges from 0 to 10% in 2.5% steps – applied to a dark stoneware and porcelain tiles.
This series were fired in a very fast and simple cone 10 reduction firing with a very basic reduction cool. 6 hours start to finish, in a small fiber test kiln — Heavy body redux for 30 min @ ^012-^08, then light redux to ^6, then a medium redux to ^10. At soft cone 11 I crash cooled a few hundred degrees, turned the air and gas down, dampered in, and put the kiln into about a -4°/minute cool, periodically opening the door to quickly crash cool -30 or -50 degrees until 1400, then shutting everything off. In some cases reduction cooling will effect the color and quality of the glazes significantly, but here it only effected the stoneware – keeping the iron oxide on the surface in its black reduced form. A good reduction firing will yield these glaze colors with no special effort cooling – here the RC was strictly for a darker stoneware color.
The Recipes
Fiske’s Tichane Chun Custer Feldspar 48 Silica 31 Calcium Carb. 20 Bone Ash 1 (Iron Oxide 1.5)
— A range .5 to 3% Iron Oxide gives a similar spectrum of blue as the basalt does here – different flavors of Iron bearing materials yield different flavors of glaze, obviously. I’ve tried probably more than 50 kinds of iron over the years – try what you have and figure out what flavor you like best!
Fiske’s Tichane Chun with 1.5% Red Iron Oxide. Fired to C10 in Reduction.
Fiske’s (Pinnell Clear) PC Celadon Custer Feldspar 25 Grolleg Kaolin 20 Calcium Carb. 20 Silica 35 (Spanish Iron Oxide .85)
Fiske’s PC Celadon with a range of 0%-2.55 Red Iron Oxide. Fired in C10 Reduction.
Basalt from 0-10%
TCB10
Mn Dark Stoneware with 10% Basalt Chun Left, 10% Basalt Celadon Right
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:
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.
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.
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.
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.
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.
Started out with Kamada Koji’s big bang glaze in mind. I’ve been completely obsessed with all glazes iridescent for some time now. This is my favorite variation to date… but still too subtle and elusive. Closer than I was, but still a lot of room for improvement.
This is the glaze I’m calling Fiske GoldFur – which came from a blend of some variations on a fake Mashiko with calcined redart, and a variation of a Britt oilspot with local black dolomite.
The center action of the GoldFur piece.
Some combination of some variations of variations.
Started out with Kamada Koji’s big bang glaze in mind. I’ve been completely obsessed with all glazes iridescent for some time now. This is my favorite variation to date… but still too subtle and elusive. Closer than I was, but still a lot of room for improvement.
Another angle of the GoldFur piece. Getting closer and closer to something completely new and completely incredible.
Ceramic Action 