Top Row: Clay Body ID's. Row 2: Salmon Terra Sigillata. Row 3: Medium Blue underglaze.
About a year ago I started testing new cone 5 clay bodies. My former low-fire clay body (fired to cone 01) was producing too many pop-outs and I could no longer use it. I have been searching for a gritty clay that would allow me to build a larger piece in one sitting. I quickly let go of ones that ended up being pale or greyed out versions of earthenware. Having the rich color of the clay come thru a slip to show texture is more important than getting lightly colored translucent glazes to show up. So here are my three finalists: Red Sculpture, SB Red, and B3-Brown.
Laguna's Red Sculpture clay body is unapologetic gritty madness. I love it. Unfortunately, it is so gritty that even when fired to temperature, it seeps water. Not good for all the vases I make, but still fine for building planters or other non-functional work. Classic toasted brown/red color when fired. Its picks up a lot of fuming (I have quite a few glazes with strontium and barium that fume). Buttery matte glazes tend to soak into the pores and - where thick are still butter mattes, but where thin- are more like a caked on incorporated surface. Also OK.
Laguna's SB Red is short for Super Bitchen. Good grog content, my buttery mattes sit on the surface, handle's well and looks well. It pops colors, and is not so dark it "eats up" lighter colored glazes. Translucent glazes over white slips show well, as do buttery mattes. A great all around clay, but I do miss the grog of the sculpture....
Laguna's B-3 Brown fires brown/black. Rich and delicious. A thinner coating of white slip looks like snow on the mountains Mmmm Yummy. Or a thin powdered sugar frosting on a dark chocolate cake. Also yummy. It has decent grit, similar to SB Red. Some slips tested well and can be seen and hold up to the intensity of the clay's own color. Unfortunately, many are "eaten away" by the clay and disappear unless very thick. The ones that hold up have an alluring intensity against the black. All my lithium/strontium/barium glazes bubble and look like burnt lava on this body. I will try something white and creamy next without those fluxes. Intriguing. I think this will be more like a wild lover than a best friend. Fiesty.
A couple of white slips with great flexibility.
I first experimented with Halifax Slip. It is the shop slip for students at Northern Clay Center. It is white, smooth, dry but not crusty or waxy. I do not know the origin of this this slip- please feel free to email me if you do. I have a second slip I like to use. I think this might be a Ron Meyers recipe? If you know for sure, please email me. I like the color I get on this slip- it is brighter, especially the chartreuse stain I like. I think this is due to the combo of Custer (potassium feldspar) primarily, but soda ash and sodium silicate. Something in this mix also causes it to crack a little. Either one can take mason stains added at will (or measured, if you are that kind of potter ;-).
I am a huge fan of copper- red copper and black copper washes with gerstley borate, and lithium/copper sulphate washes. Some of the slips have sodium silicate and soda ash in them, this will also tend to pit and make space for other color washes to pool later. Sometimes, I use my cone 6 glazes at cone 1 (see separate post for results), they are pitted and under-fired after bisquing, at which point I wash them with a copper wash, which gets in the grooves, emphasizes the surface, and fluxes out under fired glazes.
Black Copper Wash (Equal parts Black Copper and Gerstley Borate)
This concoction is inspired by an article in Ceramics Technical that sent me on a wild sulphite ride. The basis of the article was metal sulphites on porcelain, high fired- totally amazing, translucent, glowing. Be aware the sulphite is caustic/toxic while firing. I can't find the article anymore-- please contact me if you know what I am talking about. (2010). One pursuit I haven't photographed (or mastered the combo yet) is putting some of the washes UNDER glazes or slips. The copper tends to bleed through as opposed to sit on top.
Before I went to university for my undergrad degree, I was firing earthenware to cone 04. When I was in school taking clay and glaze calculation classes (with the very amazing and talented Margaret Bohls), I was researching cone 6 on a mid-range white body. Ultimately, I missed earthenware and returned to a lower temperature. I tested many of the cone 6 glazes I had to see if they would work at cone 1. I ended up settling at cone 01 for glaze firings; results being fairly similar.
Three examples of Pam with a copper wash. The glaze is brushed on greenware, fired to cone 08 or 04. It is dry and pocky (from the lithium). I put a Black Copper and Gerstley Borate wash over it. The wash fluxes out the glaze (all the boron in the Gerstley Borate) and the copper gets-- gunmetal black to variegated turquoise. Images from left to right: thinner application of Pam and thicker copper wash (this makes the thin go brown and the thicker get rivulets of turquoise and gunmetal), thicker application - 2 coats - of Pam with the wash, last image is a test tile that has half black copper wash, half red copper wash (virtually no difference).
Blue Pam (base + .4% cobalt)
I was looking for blue. I got this one on the first try (when does that happen??). I know that cobalt can raise the melting temperature, so I am surprised this still runs at cone 01! It has great variation - from waxy to semi-gloss to spotted lithium crystals where thick, if it is thin, it will be matt and dry.
Does anyone know who Pam is?
Lower-Mid Range Tests