Tag: glaze

Limestone Black Glazes

Not exactly Oil Spots in the truest sense, these two variations were concocted and tested along with the rest of my oilspots glazes. Both of these recipes utilize some local dolomitic limestone I found and incorporated into the recipes. If you want to re-create these, using a mix of 1/2 and 1/2 Dolomite and Limestone will get you very close.

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Dolomitic Limestone from Cache Valley, UT

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Shizuku Yuteki Variation

Here’s another Oil Spot I put up on Glazy.org.

You might notice that this one has a significant addition of Cobalt, half and half Custer (Potash) and F4 (Soda) Feldspars, calcined talc, and 2% Manganese. Typical that I changed too many things to give a really useful side-by-side comparison. But I suppose when I’m coming up with new variations, that’s always been my style.

2 Shizuku Yuteki Variation
Left: Underfired and immature. Cone 9/10. Right: Super long and hot cone 12 firing, with plenty of peak soak time.

Some observations on this one:

Cobalt goes a long way and pretty dramatically alters an oilspot. With a  .25%-.5% addition you get a nice shift from brown and russet glaze matrix to a darker solid black glass. Beyond 1% you can get some really nice silvery qualities to the spots. The drawback is that the more you add, the more refractory the glaze tends to get – and the longer it takes for the glazes to heal.

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Epsilon Phase Iron in Tenmoku

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:

Learning from the past: Rare ε-Fe2O3 in the ancient black-glazed Jian (Tenmoku) wares – Nature.com

Abstract

         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.

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Concrete Celadon Glaze

 

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.

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Ceramic Materials Workshop – The Middle Glazes

                         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)!!!

The Middle Glazes – The Story of Mid-Temperature Glazes

This self guided workshop is a comprehensive, 54 part study into Mid-Temperature glazes. Also known as Cone 6 or Cone 5-6, these glazes are one of the most popular firing temperatures in ceramics. They can be beautiful, enticing, engaging and incredibly frustrating. In this workshop we will explore in depth, what we know to make the most out of Mid-Temperature glazes. We will take the mystery of materials, formulas and firings and translate them for real working artists.

Topics we will Explore:

  • What is a glaze?
  • What is Cone 6?
  • Chemistry basics
  • Glaze chemistry
  • Materials
  • Understanding glaze formulas
  • Understanding cone 6 formulas
  • How temperature works
  • Glaze mapping (prediction)
  • Matte glazes and fake matte
  • Glaze durability
  • Converting Cone 10 glazes
  • Effects
  • Identifying Cone 6 glazes
  • Altering glazes
  • Problems with Cone 6
  • And even more!
For a limited time, get 25% off by using the coupon code: CMWRULES
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Linda Bloomfield – Science For Potters

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.

SP

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.

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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.

You can find this book here, or by clicking on the image below.

Glazy.org – Derek Au explains Line Blends

 

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. 

LineBlendIC

LineBlend

 

If you’re not familiar with Derek, or Glazy, I highly recommend you check him out!