Sunday, April 8, 2012

Earthenware Experiments, Round...1000.

Test Tiles

Thanks to our friend Aaron's electric kiln, I was able to get a few more earthenware glaze tests done before our firing, which happens in about three weeks. After seeing the results, I am feeling much more confident that the glazes I have been using on my pots this cycle will be both table-usable and really nice in spite of minimal testing and utilizing unprocessed, regional materials. I am excited about the possibilities for what will come out of the wood kiln.

These two "House Blend" glazes are already on plenty of my pots.
It was nice to see that they are lovely!

Here's a recap of this round for you glaze/regional materials nerds:

Those of you who know my approach know that I am not much for following someone else's recipe in the kitchen or the pottery. I look at established recipes as one would peek at a map before racing off the path. As one friend pointed out, there are easier ways to do things, but, hey, I am already in the woods. My basic earthenware glaze tests involved three simple ingredients: clay, silica, and flux. I am approaching these tests as ways to explore materials instead of finished glazes, although if they happen to look amazing in the wood kiln, I will take it!

For the clay in this round of tests, I used either EPK (as a consistent, industrially-processed benchmark) or a grey, high-silica clay from Central Iowa for my Midwest/local option. It's full of twisty roots and particles of indeterminate nature, and, in my opinion, lots more likely to make an interesting glaze. It is the foundation of the glazes in the above photo. I am gleeful when my pots, waiting patiently for the firing, start sprouting seedlings from their rims. I used this clay as it came out of the ground--no ball milling or sieving for this gal if I can help it!

For the silica, I used what we here at WRP call "bunker sand." The quarry in south-central Wisconsin where it comes from claims that is a favorite sand-trap material for discerning golf courses. Those of you who have been long time WRP fans may remember our first firing in which we used it with disastrous results in our wadding. So, we know it's not pure silica, but I thought it was my best option as a silica stand-in, complete with a free dose of feldspar. It comes in sand-sized and we ball-mill it to usable size. By "we" I mean "Joe." Thanks, honey!

For the flux, I don't have a good local or regional option. Ironically, the community we live in was founded on lead mining, and the hills around us are pocked with remnants of mines. Lead was historically coveted for making incredibly beautiful low-fire glazes that poisoned their makers and lots of their users. Although there are safer ways to use lead today, I just don't want to go there, so I am testing Gillespie Borate and Soda Ash.

I mixed blends along the lines of x part flux, y part clay, z part bunker sand. Here are a few examples:

Right: 1 Gillespie/1 EPK/.5 Bunker Sand
2 Gillespie/1 EPK/.5 Bunker Sand
Both quite dry, but interesting for texture.

Right: 2 Gillespie/1 Iowa Clay/.5 Bunker Sand
Left: 1 Gillespie/1 Iowa Clay/.5 Bunker Sand
These look better in person than in the photo!
I am looking forward to seeing them in the atmosphere of the wood kiln.

Tests that will go into the wood kiln will also incorporate our local favorite Ivey Red Clay (small particle, dolomite infested, tragically beautiful earthenware clay) from just south of town, Ivey Sand (dolomite) from here in town, Iowa Limestone (calcium carbonate) from Northern Iowa, Corn Ash (a possibility for fluxing! )and whatever else I can dig up, mix into a glaze, and put on a pot!

A testing recap would not be complete without a shout-out to our favorite geologist Don Campbell. Not only has he helped us physically track down small pockets of true limestone in a land of dolomite, but he tests samples of materials for us and writes back with fabulous technical information like:

"Traces of quartz silt (particles with sizes of approximately 35 microns), less than 0.25 to 0.50%, occur in both samples, the gray sample having the higher percentage. The gray sample also contains traces of chert (flint, SiO2)."

We are so grateful to have his help as we tromp around the Midwest looking for clay and glaze materials that reflect our landscape and give our pots surfaces that could only come from right here, right now.



angela walford said...

ahh christy the quest continues and you are indeed soldiering on!! I hope your sources continue to be the geek out expose too :)) hope you have a brilliant firing

deanandmartinpottery said...

Love the dry surfaces Christy!! XOXO

Joe and Christy said...

Thanks, Ang, Jeff, and Steph! I am really looking forward to seeing where our wood firing takes everything!