So these glazes were my second attempt at iridescent surfaces. I tried some copper, upped the manganese in several glazes, and also tried granular manganese, granular magnetite, and granular ilmenite. The Fake Mashiko turned out really nice, not at all iridescent, but nice.
One thing to note is the all of the tiles on the left were from firing #38, which was a small test gas kiln. It wasn’t a very good firing to say the least. The tiles on the right were from firing #40, which was an extremely long, extremely hot firing. The schedule was something like 4 hours between cone 7-8, then about 5 hours between 9-10, an hour to cone 11, and another 2 hour soak around cone 12. Pretty extreme for a gas kiln, I think. On the other hand, that’s nothing compared to some Anagama firing schedules.
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!
Here’s an interesting glaze inspired by a locally abundant material – dead palm fronds. Every week throughout South Florida the streets fill up with piles of dead vegetation from people pruning their trees and plants. With a 12 month growing cycle, they’re EVERYWHERE.
To utilize this stuff, I started by collecting about a half of a pickup truck’s worth of dead palm fronds. Collecting all of this stuff took about 10 minutes, and I didn’t have to go very far. I then setup a perforated burn barrel with a grated floor. I burned down everything, and collected the ash in a tray under the barrel. Once I collected the ash, I added it all to a 5 gallon bucket and ‘washed’ it, by dumping out the top layer of chunks and oily looking stuff. I gave it 24 hours, and came back out and stirred it, and repeated for the next few days. Fin ally, I poured the mix through a 40 mesh sieve into a bisque drying platter and let the stuff dry out. After that I crushed it into a powder and pushed it through an 80m sieve. Quite a bit of work, but a truly unique material.
Given that the soil here in Florida has so much Silica by virtue of all the sand it contains, I had the thought that its be likely that palm tree ash would have a much higher % of silica than say, hardwood ash. I haven’t had it tested for the side-by-side chemical composition, but my initial tests seem very promising. My next step is to dredge up some clay-like muck from the canal across the street, and mix in calcined seashells for good measure. If the canal silt doesn’t do the trick, I’ll try some clay/silt from the Intracoastal waterway (A brackish salt/freshwater channel that runs parallel to the ocean, inter-connected by inlets and canals – which ultimately keeps South Florida from turning back into a swamp!)
Nontheless, the 3 tiles on the left were soda fired. The 2 on the right were Reduction fired to cone 10/11. The clays from left to right are; Studio Reclaim (A bastard mix of everything), B-Mix, 550 Porcelain, Studio Mix, Porcelain. The recipe is as follows:
Fisker’s West Palm Ash
Unwashed, 80m Palm Ash 45
Nepheline Syenite 45
Redart Earthenware 10
Here’s the newest round of slips for leather hard/stiff application. All but #7 will work for bone dry application. Not tested (yet) for bisque application. Fired to cone 10 flat in a hard reduction. Left side is super thick, right side is thinner. Clay body is a Hawthorn/Goldart/OM4 stoneware – nothing fancy.
#1 Greenware Slip: Grolleg Kaolin 40, OM4 Ball Clay 10, Custer 25, Silica 25
#2 Greenware Slip v.1: EPK 25, Grolleg 25, OM4 Ball Clay 10, Custer 25 Silica 25
#3 Bringle Slip: EPK 20, OM4 20, Neph. Sye. 25, Silica 30
#4 BS v.1: Grolleg 25, OM4 25, Neph. Sye. 25, Silica 25
#5 BS v.2: Grolleg 30, OM4 10, Neph Sye 20, Silica 20
#6 Coleman Clay: EPK 50, Silica 25, Custer 25, Frit 3110 5
#7 CC v.1: Grolleg 50, Silica 25, Custer 25, Frit 3110 5
#8 Porcelain Slip: Grolleg 30, OM4 8, Custer 30, Silica 30, Bentonite 2
The light is cheating these a little bit. #1,2, and 8 seem to be the whitest, with not much differentiating them. #1 seems to promote the best celadon blues, although timing is critical, because it cracked when applied to a bone dry tile. #2 seems to be a perfect middle ground in terms of versatility, cost, and whiteness. In my experience, the difference between a 50/50 grolleg/epk and a 100% grolleg clay body is negligible in cone 10 reduction. The case could be made that it really matters in oxidation – which is just now bringing to mind the need to test these in c6 oxidation.
My picks? For Whiteness:
EPK 25, Grolleg 25, OM4 10, Custer 25, Silica 25, 45cc Water, 5cc Darvan #7,
For Celadon Blue:
Grolleg 30, OM4 8, Custer 30, Silica 30, Bentonite 2, 50cc Water, 5cc Darvan #7