Oilspot Firing Schedules

Here’s my Lava Oil spot firing schedule, which always looked best fired in a neutral/oxidation atmosphere in a gas kiln.

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.

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.

Shizuku Yuteki Oilspot

Just spent a bit of time inputting this old recipe into Glazy.org. Pretty Sweet!

Chen Xu

Here’s a stunner from Chen Xu at the https://www.tenmoku.com/blog

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.

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.

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.

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. 

 

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

Leonard Smith – Modern Jian Ware

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!

John Britt explains Ian Currie Systematic Glaze Blend!

My favorite way to systematically tweak a ceramic “Base Glaze”. John does a great job explaining it!

He can be followed on YouTube @ https://www.youtube.com/user/johnbrittpottery

And you can find more on his website @ https://johnbrittpottery.com/

 

 

Basalt as Colorant in Celadon Glazes

Basalt as Colorant in 2 Base Recipes.

More local Basalt. Here used as colorant in high fire celadon glazes. On the top left, the raw material which was collected from various places throughout Idaho and Utah (and all mixed together), bottom left the homogenous, calcined, milled, sieved, and dried material ready for glaze.

In this set the basalt is supplying the iron necessary for that timeless celadon blue. Its also bringing significant additions of magnesium and calcium to the recipe. The % of basalt here ranges from 0 to 10% in 2.5% steps – applied to a dark stoneware and porcelain tiles.

This series were fired in a very fast and simple cone 10 reduction firing with a very basic reduction cool. 6 hours start to finish, in a small fiber test kiln — Heavy body redux for 30 min @ ^012-^08, then light redux to ^6, then a medium redux to ^10. At soft cone 11 I crash cooled a few hundred degrees, turned the air and gas down, dampered in, and put the kiln into about a -4°/minute cool, periodically opening the door to quickly crash cool -30 or -50 degrees until 1400, then shutting everything off. In some cases reduction cooling will effect the color and quality of the glazes significantly, but here it only effected the stoneware – keeping the iron oxide on the surface in its black reduced form. A good reduction firing will yield these glaze colors with no special effort cooling – here the RC was strictly for a darker stoneware color.

The Recipes

Fiske’s Tichane Chun
Custer Feldspar 48
Silica 31
Calcium Carb. 20
Bone Ash 1
(Iron Oxide 1.5)
— A range .5 to 3% Iron Oxide gives a similar spectrum of blue as the basalt does here – different flavors of Iron bearing materials yield different flavors of glaze, obviously. I’ve tried probably more than 50 kinds of iron over the years – try what you have and figure out what flavor you like best!

Fiske’s Tichane Chun with 1.5% Red Iron Oxide. Fired to C10 in Reduction.

Fiske’s (Pinnell Clear) PC Celadon
Custer Feldspar 25
Grolleg Kaolin 20
Calcium Carb. 20
Silica 35
(Spanish Iron Oxide .85)

Fiske’s PC Celadon with a range of 0%-2.55 Red Iron Oxide. Fired in C10 Reduction.

 

Basalt from 0-10%

TCB10

Mn Dark Stoneware with 10% Basalt Chun Left, 10% Basalt Celadon Right

Celadon with 0-10% Basalt

Basalt Celadon 7.5%, 10%

Basalt Celadon 0%, 2.5%, 5%