Let’s get back to the pottery now, shall we???? 🙂
Ok folks, this is quite long so get your cuppa coffee or bevarage of choice. I was going to try to keep this brief, but found that writing was helping focus my thinking about the results and where I want to take them. If you’re not interested in the technical aspects of glaze testing, feel free to skip to the end, where photos await! 🙂 However, as I myself read the ins and outs of every glaze testing report I could find before I fired my first kiln, I kept this as detailed as possible. Hopefully this information will indeed be interesting and helpful to someone out there! As folks will tell you, there is no replacement for running your own tests. I found this to be indeed true and happily, next round of glazing will be much more focused.
But I digress! As many of you know, this was my very first glaze firing in my new L&L e-28s and the first time that I’ve mixed up glazes in Puerto Rico. In the UK, I fired to cone 8-9, but I’ve decided to go down to cone 6 for economic reasons. However, as I was very impressed with the lovely range of Cone 6 glazes out there, it really was not a big sacrifice. It did mean I was starting from scratch as far as glazing was concerned! This was my first round of glaze testing.
My goals in testing were to:
- assess glaze fit and appearance on the two clay bodies I’ve been testing: Standard 240 and Axner’s version of B-Mix, Maccabbee (Mix 5). From my throwing experiences, the Standard 240 is so far winning the race.
- narrow down the list of glazes I want to mix up in large quantities
- identify interesting glaze interactions/overlaps for future work
- develop a nice celadon-like green glaze for my Sea-Grape plates
- develop another brown glaze
- successfully fire a cone 6 glaze kiln (following MC6G guidelines and firing schedule) for the very first time!!!!
I mixed up batches of the following glazes from “Mastering Cone 6 Glazes” by John Hesselberth and Ron Roy (see book for recipes):
- Raw Sienna (1000 grams)
- Waterfall brown (200 grams)
- Bright Sky Blue (500 grams)
- Variegated Blue (500 grams)
- Licorice Black (500 grams)
- Glossy Base Glaze 2 (100 grams)
- Glossy Base Glaze 2 + 1% copper carbonate (200 grams)
- Glossy Base Glaze 2 + 3% copper carbonate (200 grams)
- Glossy Base Glaze 2 + 6% RIO + 4% Rutile (200 grams)
- High Calcium Semimatte Base 2 + 1% copper carbonate (200 grams)
- High Calcium Semimatte Base 2 + 0.5% copper carbonate, +0.5% cobalt carbonate (200 grams)
I had prepared a good amount of small work (espresso cups, small bowls, handbuilt plates) for glazing. As I’ve previously mentioned, I could not fathom filling my 28-S (all 6.8 cubic feet of it) solely with test tiles. I realized going in that this was a bit risky and potentially a lot (even all) of the work would be a wash. But hey, I got a good amount of throwing practice out of it and the name of the game is testing, right? All work was bisque fired to cone 04, as per MC6Gs recommendations.
The recommended minimum amount for a glaze testing by the authors is 200 grams of glaze, which is really not much at all! It is fine for dipping test tiles (of which I had many) and was also useful for very small test items (shell pendants, magnet disks). I also was able to use the smaller quantities by pouring into (then out) of my small espresso cups. On the other end of the scale, 1000 grams is quite a good amount of glaze, and I was able to glaze the way I normally do, by using tongs or holding wares to complete quick “in and out” dips. The resulting glaze application was even and thinner than any other method I used to compensate for smaller amounts of glaze. I found that 500 grams was a much better amount for my purposes than 200 grams. I was able to dip larger pieces (especially if I was only applying to glaze to part of a pot) but still didn’t have the “depth” for complete quick dips. This of course resulted in greater glaze thickness (and not the most even glaze application). But glaze application with 500 grams of glaze was indeed closer to how I normally would work with glazes.
Before I share photos of my results, a few findings, observations and reflections:
First, regarding the new recipes I mixed up (variations on MC6Gs):
- Glossy Base Glaze 2:
Nice transparent glaze. With the Standard clay, this means slightly yellowish (really only noticeable to me when held up against a whiter clay body). I tested it with some Mayco Stroke and Coat underglazes and the underglazes showed up true to color under this glaze. In other words, it was transparent! 🙂
- Glossy Base Glaze 2 + 6% RIO + 4% Rutile (Temporary name, variegated bluish-brown):
Boy we liked this one! It is brownish/mauvish/creamish/bluish in its variegation. When very thin (and where it breaks on patterns), it is a lovely brown. Beautiful. Definitely mixing up a larger batch to further test this one
- Glossy Base Glaze 2 + 1% copper carbonate and Glossy Base Glaze 2 + 3% copper carbonate:
Both give nice greens. The smaller percent does look like a very light celadon (on my light clay body). The higher percent is quite a vivid green and Nick is quite partial to it. Both would work well for my dishes but I think we’ll also try 2% next time! 🙂
- High Calcium Semimatte Base 2 + 1% copper carbonate:
A nice, even covering semimatte glaze, light green with delicate light crystals. Created some really glaze effects when poured over Licorice Black and Raw Sienna (kinda like “Hare’s fur”)
- High Calcium Semimatte Base 2 + 0.5% copper carbonate, +0.5% cobalt carbonate
Very nice blue and again, as above, nice glaze effects with Licorice Black and Raw Sienna. Will continue to explore.
- As far as glaze application goes, the glazes all went on the clay bodies very nicely. They dried to a hard shell (i.e., not powdery) which made it easy to handle and multiple dip pieces.
- For a first firing, I was very happy with my results. No major catastrophes (I was well prepared for glaze runs with 3 layers of kiln wash AND kiln washed biscuits under each piece but suffered none!), lots of awesome results, lots of learnings and good focus for future experiments AND future glazing.
- My Variegated blue and Bright Sky Blue could have (should have) been a tad thinner. Due to the application challenges, a few areas were clearly too thick. Where very thick, the variegated blue pinholed a bit.
- Overall, the glazes (at least to my eye) present as they do in the book on porcelain. For example, my variegated blue looks a lots like figure 6-12 in the book and not at all like figure 2-5 (which is unfortunate, as the latter is actually the look I prefer). Perhaps this would be different if the glazes were thinner? Not so much? As we used to say in academia, “It’s an empirical question!” and more testing will reveal the answer.
- I could see no major differences (to the naked eye) vis-a-vis glaze fit for the Standard and Axner clays. All glazes stayed put (no running below glazing line) on both clay bodies, expect for the waterfall brown of course.
- My one “complete wash” of the firing was a bowl with waterfall brown poured into a bowl, swished around to cover, then out. I applied licorice black to the outside. The resulting glaze application of waterfall brown was clearly far to thick on the inside bottom of the bowl (where the glaze most have also pooled down the side), and actually blistered! As I kept the glaze inside the bowl, no harm done, major lesson learned! 🙂 Test tiles and small flat pieces with waterfall brown show its promise and I’ll keep playing around with it.
- The bright sky blue is VERY bright. I can see using it in combination with other glazes but probably not on its own.
- I mixed up a nice sized batch of Raw Sienna as I thought it would be a winner and it was! Very nice brown with slight color variation and subtle changes from matte to glossy where thickness varied and nice crystallization. Looks really sharp with Licorice Black but also interacts nicely with Variegated blue.
- Licorice Black is lovely. Smooth black, and interacts well with other glazes (a characteristic that is very important to me). Where it breaks (on texture and rims) it broke brown. Favorite combos: under and over variegated blue and over and under bright sky blue.
- Other combos I really liked: Variegated blue over Raw Sienna, Variegated bluish-brown over licorice black, raw sienna over black.
- Standard 240 fires to a creamy slightly yellow color (see following pictures) whereas Axner’s Maccabbee fires more white/gray. This is most evident in the comparison of the two clay bodies with Basic Glaze Base 2. This is not an issue for me but it might be for others.
So now, without further ado, here are some images (click on any image to enlarge). First, test tiles with single glazes. The back row is Standard 240 (top of tile was double dipped), the front row is Axner’s Maccabbee (single dip).
Verigated blue, Licorice black and Raw Sienna
Waterfall brown, Bright sky blue and Glossy base glaze 2 (note visible difference between the two clay bodies for the latter).
GBG2 with 3% copper carb, GBG2 with 1% copper carb & GBG2 with 6% RIO + 4% Rutile
HCSB2 with 0.5% copper carb & 0.5% cobalt carb, HCSB2 with 1% copper carb
The following images illustrate my favorite results from the firing:
Wheel thrown cup (2×2.5inch). Standard 240. Licorice outside, Bright sky blue inside (overlap on inner rim)
Wheel thrown cup (2×2.5inch). Standard 240. Raw Sienna (glazed in one dip)
Wheel thrown cup (2×2.5inch). Standard 240. Black licorice outside, Variegated bluish-brown inside (overlap on rim)
Wheel thrown bowl (4.5inch diameter). Standard 240. Varigated blue over licorice black
Wheel thrown bowl (5inch diameter). Standard 240. Bright sky blue over Licorice black
Wheel thrown bowl (5inch diameter). Standard 240. Licorice black, Raw Sienna with HCSB2+.5%copper carb+.5% cobalt carb poured over overlap and negative space
Hand-built plate (3.5×3.5inches), Standard 240. Variegated bluish-brown over Licorice black
Hand-built plate (3.5×3.5inches), Standard 240. Raw sienna over Licorice black.
Handbuilt slab vase (5x3inch) textured Axner Maccabbee. Variegated blue over Raw Sienna
So what’s next? I plan to mix up larger batches (1000-2000 grams) of a few of the glazes and mid-sized batches (500 to 1000) of those I’m not quite ready to commit to yet but want to further explore. I can forsee having some glazes that never get mixed up in batches larger than 1000 grams, as I only use them as “special effects” glazes (e.g., bright sky blue). Time will tell!
There are a few more small batch (200 grams) experiements I’d like to try out, based on the results of this firing (e.g., playing around a bit more with levels of copper carbonate in GBG2). And, I want to play around with the colorants in Licorice a bit to get a deep brown (of course, Licorice Black is definitely staying on the menu!).
I’m also planning to mix up some Raspberry (from MC6Gs) and Jeannie’s Purple, which is based on Raspberry. By now, I have amassed a large number of cereal sized bisqued bowl for the next stage of glaze testing. I will also throw a bunch more of the small bowls I used this time (wheel thrown from 12 ounces of clay), which proved an excellent size for testing glaze combos, even with the smaller (e.g., 500 gram) glaze quantities. My head is exploding with ideas, and I finally have some REAL finished pots! Very exciting!