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Silicon Carbide in glazes

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Has anyone had any luck adding silicon carbide to glazes.

 

I found this blog by Jon Britt Silicon Carbide reds which basically says put some silicon carbide 600 in your red reduction glazes and something nice will happen when you fire them in oxidation. Well, I tried this in many different glazes and I got the most bubbly, ugly nasty glazes you can imagine. I used Stephen Hill's firing schedule, which has a couple of long holds.

 

Back in February Jon promised to disclose the secret. I have posted a comment on the blog prompting him to follow through... no luck.

 

Has anyone tried this with success? Does anyone know how to light a fire under Jon to get him to follow through?

 

Has anyone found silicon carbide good for anything else in glazing?

 

Thanks Larry

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Hi Marcia

 

I had no idea what to use. So I just put in a "pinch and a smideon"... sometimes quite a bit and sometimes just a little .. all on test tiles.

 

Any ball park idea what would be appropriate.

 

I regularly do hundreds of test tiles so if I had some vague idea what made sense, I could run some tests..

 

Larry

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Hi Marcia

 

I had no idea what to use. So I just put in a "pinch and a smideon"... sometimes quite a bit and sometimes just a little .. all on test tiles.

 

Any ball park idea what would be appropriate.

 

I regularly do hundreds of test tiles so if I had some vague idea what made sense, I could run some tests..

 

Larry

 

Larry... Tom Turner has put a lot of time into studying chemically reduced copper reds in oxidation. He uses silicon carbide in copper red glazes that he fires in oxidation instead of reduction. He says that too course of a grind causes bubbling. He uses 800 mesh, FFF grade or finer from Washington Mills. He uses very small amounts of silicon carbide--1/3 to 1/2 percent. Here is his article from Art & Perception/Technical: http://www.tomturner....com/page25.htm . Hope this helps. Let us know what happens.

 

Jim

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When doing test tiles, if you want to repeat a success or avoid a failure, it is nice to know what you used. Silicon Carbide is one of those chemicals that should be used very sparingly. Otherwise it can "roil" the surface of the glaze. Particle size is also very important. Turner does a great job of laying it all out. Thanks for the article, Jim.

Marcia

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The Turner article is really good. That was me a giant step forward for me. I just squeezed out about 500 more test tiles keep testing this stuff.

 

I understand that to get repeatable results one needs to have good measurement. I don't have measurement of how much silicon carbide I added because I was using some leftover bits of glaze from from trying reds in my gas reduction kiln. I finally gave up on my very cranky Olympic gas kiln angry.gifand bought a Scutt electricrolleyes.gif, which seems much more manageable.

 

Larry

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Larry,

 

Your query prompted me to re-read an early paper on the subject:

THE PRODUCTION AND CONTROL OF COPPER REDS IN AN OXIDIZING KILN ATMOSPHERE

Arthur E. Baggs, Edgar Littlefield

Journal of the American Ceramic Society

Volume 15, Issue 5, pages 265–272, May 1932

... the abstract is freely available at:

http://onlinelibrary...3930.x/abstract

 

For those without access to the contents of the paper, here are a few comments.

 

(1) They obtained a cone 9 copper red with 0.3% copper carbonate and 1% silicon carbide.

 

(2) They experimented with the silicon carbide in an under-glaze, using it in two ways: as an

engobe/slip fired on bisque, and as an inlay in incised decoration on a green-ware. In both

cases the under-glaze was fired before the silicon-carbide free glaze was applied and fired.

 

(3) They experimented with multiple colours on the same pot. Upping the copper content and

adjusting the glaze composition to give a green or blue glaze in oxidation. So by using reducing

under-glaze as an inlay or over parts of the pot you get a green (or blue) pot with red detail.

 

(5) They give under-glaze/glaze combinations for copper reds at cones 012 and cone 9.

 

(6) They suggested that silicon carbide achieves reduction-effects over this remarkably wide range

by only reacting when in contacted with liquid glaze.

 

(7) Cone 012 firings.

These used an engobe containing from 1% to 10% SiC fired at cone 06. [They did this

early in their tests, and I suspect that 0.5%-2.5% SiC is a more interesting range.]

The green and blue multicolour effect glazes contained 1% and 2% CuCO3 respectively.

[A low copper glaze fired in oxidation is pale to colourless.]

 

(8) Cone 9 firings.

For a simple in-glaze reduction copper-red they used 0.3% CuCO3 and 1% SiC.

I don't think that they reported green/blue glazes cone 9.

The reductive under-glaze was a slip made from the clay body plus from 0.5% to 2.5% SiC

and was fired to cone 3.

 

Overall a much more interesting paper than I remembered.

 

Regards, Peter

 

PS Some random thoughts.

 

(i) Use of multiple strengths of reductive under-glaze on the same tile might reduce the

number of test-tiles you need to fire (and glazes you need to mix). Even if you intend to

switch to in-glaze reduction near the end of your trials.

 

(ii) The late Ian Currie's admirable book "Stoneware Glazes" is viewable online. The section

on copper-reds is well worth reading (although it only mentions local reduction in passing).

http://stonewareglaz...o/book/page/189

For those unfamiliar with this great book, it is in two very different sections. The first deals with

glaze testing and Currie's grid method. The second is a remarkably detailed overview of a wide

variety of stoneware glazes.

 

(iii) Considering copper's volatility at high temperatures, a protective over-glaze might

be worth trying when you've got things working.

 

(iv) Several people have used silicon as a local reducing agent (e.g. mentioned in Parmalee).

An obvious advantage is that it does not out-gas. This can be a little trick to source, but a google

search for silicon powder mesh 1lb will return a few good hits and a lot of bad ones (mainly

relating to silica or silicon carbide). For example:

http://www.pyrodirec.../Item/093-0305r

... which is currently out of stock

http://www.westernpyro.org/

... look under "Chemical Vendor Order List" to find 20 micron (625mesh?) silicon @ $8/lb

 

... and a search for silicon micron at www.amazon.com will find

http://tinyurl.com/pmqnpsr

Joseph F likes this

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Peter

 

Wow ! This is really useful information. The summary is very nice, particularly considering the cost of Journal of the American Ceramic Society. It gets me started again fiddling with silicon carbide in my glazes. The stuff seems to have great potential, if you can figure out how best to use it.

 

Thanks

 

Larry

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Tom Turners article on oxidized copper-reds is brilliant.

It does however emphasize the unavoidable truth that the only way to get the results you require is to spend time on testing and experimenting for yourself in your own conditions.

David Leach produced some beautiful `bullsblood` pots (early90`s), of which he was justifiably proud, but he never told me if they were reduced or not.

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I am going to bump this old thread. I recently started experimenting with this. These tiles are different thicknesses 1-3 dips(L->R). 

 

post-63346-0-30745700-1495221637_thumb.jpg

 

This is the glaze recipe from John Britt's Book. Copper Red. Which is reducing using SiC. I also tried using a slip under the glaze before adding the SiC. It came out like a crater glaze. Where this came out pretty nice with only a few visible defects. The crater version still had reduction, I could see spots of red, however the surface was not what I was lookign for.

 

1. Where is the blue coming from? The recipe contained 2 tin oxide, 1.5 copper carb, and .8 SiC. These tiles look nothing like the ones in JBritt's book. Which is normal, except his have no blue anywhere. I am really confused by the blue. 

2. From post earlier Peter said the SiC best reduces in a liquid environment. This seems to be true on these tiles as the thicker they are the more reds appear.  

 

It is all interesting stuff. I am not sure where I should go next?

 

I will say that my surface is a lot smoother than I imagined it would be. I only have small pinholes that I could probably fill with a longer hold, although I do not understand the ramifications of the longer hold burning out the SiC or not. I think I will continue to test a small amount of these test each firing. It could develop into something interesting.

 

Does anyone know what temp the SiC starts stealing oxygen?. I would like to hold there for better results.

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Found this: 

 

7.4. Blue color can sometimes be obtained during the elaboration of copper reds, apparently due to surface layer effects. According to the intensity of the effect, one can obtain different hues: greyish, violine, purple and pale or strong blue. This effect deserves by itself a special study. In the same way, some authors [8] have emphasized the importance of a thin red surface layer for the final quality of color for the pieces they have studied. The influence of this kind of layer could be evaluated or modelised with the help of the results or methods of the present study.

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I still have a mug from the 70s with a silicon carbide local reduction red. /chun blue kind of glaze and a tumbler the a more even red. If I remember the amount of silicon carbide was minuscule. like 0.2% ranges.

Marcia

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I bought some silicon carbide powder about 38-40 years ago and played with it with poor results. that was in the 70's-Cone 5 was not a temp most stoped at back then. Maybe it has more applications now?

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http://www.westernpyro.org/

... look under "Chemical Vendor Order List" to find 20 micron (625mesh?) silicon @ $8/lb

 

When I've had students do research on this technique, the fine-ness of the SiC was of HUGE import to the potential success they found.  The typically available mesh sizes at most "pottery suppliers" was far too coarse.. and got the "big bubbles" mess.

 

best,

 

.............john

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The grit/mesh I used in those tiles was 1200. I got it from a polishing company. I don't get big bubbles but I do get little pinholes from the gassing of oxygen. I am going to abandon the issue for now. I have more important things to figure out.

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Joseph:

 

The big issue with SiC is its melting point... check that out. I have used calcium borate, lithium carb, and lithium hydroxide in an attempt to get it to melt at cone 6. I have even tried anisotropic etching, which did help. ( and no I will not explain that process, too dangerous if you do not know what you are doing.)

RedinOx^6Test5

 

This is the best I have gotten at cone 6

 

Nerd

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