For those of you who are really interested in Oil Spots, there’s an article from 2014 that I think is worth a long look. This particular article was what got me interested in SEM microscopy when I was in Grad School:
Ancient Jian wares are famous for their lustrous black glaze that exhibits unique colored patterns. Some striking examples include the brownish colored “Hare’s Fur” (HF) strips and the silvery “Oil Spot” (OS) patterns. Herein, we investigated the glaze surface of HF and OS samples using a variety of characterization methods. Contrary to the commonly accepted theory, we identified the presence of ε-Fe2O3, a rare metastable polymorph of Fe2O3 with unique magnetic properties, in both HF and OS samples. We found that surface crystals of OS samples are up to several micrometers in size and exclusively made of ε-Fe2O3. Interestingly, these ε-Fe2O3 crystals on the OS sample surface are organized in a periodic two dimensional fashion. These results shed new lights on the actual mechanisms and kinetics of polymorphous transitions of Fe2O3. Deciphering technologies behind the fabrication of ancient Jian wares can thus potentially help researchers improve the ε-Fe2O3 synthesis.
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.
It’s been pretty cool to watch Ceramic Materials Workshop develop into what it’s become. Matt and Rose Katz are building an amazing thing, and their list of glaze disciples pushing the envelope of glaze magic has grown steadily. I’d planned to become an initiate myself and take the October class… but life on a remote island in Southeast Alaska has it’s own demands on my time, attention, and energy. That said, I just got this info from CMW in my email, and it looks great – certainly in line with what Ceramic Action is all about. I’d encourage you to check it out, you can not go wrong. You can even use the code CMWRULES and get the whole shebang for 75$ (Less than the cost of my average bar tab)!!!
Fans of the blog will have noticed a lot more activity of late. It seems like one of my favorite old adages is appropriate: Good things come to those who wait. Rather than over promising on a bunch of ideas I may or may not deliver on, I’ll go with another one of my favorite adages: Actions speak louder than words. That last one seems… pretty appropriate.
In any event, I’ve been working on putting together a recommended books section, and felt like I might as well start with one that I’m in! regardless of that last fact, it couldn’t be more appropriate to what this blog is all about.
A few years ago when I was neck deep in my Lava Oilspot research, Linda reached out and asked me to contribute some images and information for this book. I couldn’t have been happier with how my work and images were presented. It’s got all kinds of useful information on connections between rocks, glazes, ceramics, and chemistry.
It’s thoughtfully put together, and if you’re looking to get a handle on using wild materials or learning more about some clay chemistry, this is a great one to check out.
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.
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!
@son_of_a_bisque gives a perfect example of how to develop a glaze from local materials. In this case we have shale, and wood ash. After this initial line blend test, I might run another line blend to zoom in on whichever glaze suited me best. (Personally think something like 60 Shale:40 Ash would probably be killer!)