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Bob Coyle

Member Since 06 Jun 2013
Offline Last Active Jul 23 2015 08:26 PM

#89119 Stretching Your Limits

Posted by Bob Coyle on 18 July 2015 - 08:22 PM


I found that those had one continuous spiral crack running from 1" from the bottom all the way up to 1" from the rim. Like a spring! Hmmm. after lots of research, and talking to others including the folks at SC clay, I changed my firing schedule and had no problems.


Sometimes not all is a disaster, and a little help and research might help.

When I was doing engineering we "stressed to failure".  That was the ONLY reliable way to see how far a limit could be pushed in a real world situation. We pushed the limits till it failed... re-tweaked and tried again. Failure is absolutely essential... just as long as you are in a position to set things up so you learn from it... like Pres.

#87797 Clay Storage Environment

Posted by Bob Coyle on 26 June 2015 - 11:51 AM

I have had good luck with storing my clay in closed 20 gal plastic bins. I put a open container of water on the bottom and it keeps the clay from drying out through the plastic.

#74852 Firing A Sculpture With Aluminum Alloy Armature Wire Inside?

Posted by Bob Coyle on 04 February 2015 - 08:06 PM

if the wire is all connected together and is sticking out so that it is exposed to the atmosphere, you might be able to just melt it out and let it oxidixe without blowing anything apart.

Put a good layer of kiln wash on your shelves and bring it slowly up to around 1300F. This is above the melting point but below the boiling point. So all that should be happening is oxidation to the oxide , which is inert.

hold it ther for a couple of hours. Thin sheets or wires of aluminum oxidize quickly. That should melt/oxidize out the aluminum and give the clay enough strength to re- fire it after the aluminum has oxidized out.


It's worth a try.... any other way you will probably lose the sculpter.

#71021 Is There A Way To Distinguish Low-Fire From High-Fire Clay Piece?

Posted by Bob Coyle on 01 December 2014 - 11:56 AM


You could put the whole piece into a larger bisqued high fire bowl and then fire to cone 10 and when it melts its all contained in the bowl.
Thats the only way to avoid a disaster

Like Mark says...  Long ago I thought it would be neat to paint pictures on the surface of some commercial tiles I bought. They looked like high fire to me, besides I was just firing to cone 6... what could go wrong.


Well when I opened the kiln, there were no more tiles, only blobs firmly melted into the kiln shelf. Betcha I don't do that again.

  • Mug likes this

#70117 Input Would Be Great!

Posted by Bob Coyle on 17 November 2014 - 08:38 PM



I also like the look of Rebekah's forms. To me, this is how a beer stein/mug should look. I threw several similar forms for the prototypes I put out. Some people liked these (the more classic look) and some like the obvious " hand built" look which kind of surprised me. So I will do both for the up coming beer fest.


The manganese glaze/slip on the handle is one I poster here a while ago. I got a lot of comments that said it was not "food safe". which may be true, but I usually don't make stuff people eat  or drink from. I think it is fine for a handle though. I fire to cone 5-6 and I have made sculptures with this stuff that were copper plated for four days in a copper sulfate /sulfuric acid solution and the glaze  didn't look like it was effected so it won't come off in the dish washer.

below is the formula is you want to try it.


Ingredient                  Parts
Rutile                       27.00
Red iron oxide          26.00
Manganese dioxide   20.00
Ball clay                   10.00
Flint                           8.00
Frit 3134                    6.00
Copper carbonate       4.00

#68822 Tinkering With Commercial Glazes

Posted by Bob Coyle on 28 October 2014 - 06:11 PM

I never do anything other than brush glazes. I always use an polymeric brushing medium, rather than bentonite. The brushing medium, CMC or PEG or whatever forms a high polymer binder that literally sticks the glaze together on the surface of the pot, then burns off in the firing. I have never had trouble with flaking or any loss of glaze from the surface. I buy a ready made binder from the local clay store...probably mostly CMC... that has a mold inhibitor included. It costs more but is less of a hassle... no fermentation and stink.


The only problem I have with brushing, is that my students ALWAYS want to paint it on too thin. Once they learn to FLOW it on. the gazes look fine, and I don't need 5 gal pails of every glaze.

  • Mug likes this

#67899 Art Deco

Posted by Bob Coyle on 16 October 2014 - 10:02 AM

Yes Chilly, I think the word you are looking for is "Re-muddled". Sadly a lot of great old architecture was forever lost to a false idea of progress.

#67609 Setting An Electric Kiln Outside

Posted by Bob Coyle on 11 October 2014 - 01:36 PM

I had a old Kress kiln I kept outside and all I ever did was wrap it with tarps and attach bungees around it. The only problem I had was making sure it was wrapped tight around the bottom to keep the mice out. I used it that way for ten years,without a problem, until I moved.




You must live in some uptight community is it is not enough to allow a home owner to build to code... sounds like the contractors there have purchased the local politicians.

#65664 Making Cone Packs

Posted by Bob Coyle on 05 September 2014 - 06:38 PM

The lowest cone value should be first in the direction they lean. I always put the flat side toward the direction they will sag. I think this is the way recommended...pretty much like the picture. I never have used a protractor to measure angle. I just make sure that they are slightly bent towards the direction I want them to sag. if you wish to be more precise, that's fine. I like to fire my pieces to the point the middle cone ( the range you are looking for) touches down. Of course there should be three cones, one above and one below the cone you are shooting for. I leave just enough room for my cones not to hit each other when they sag. The lower ones should be pretty much down before the next one sags, so they can be within a cones width of each other. You want to be able to see them all through the peep hole.


Remember, firing a kiln load of ware is not something that can be absolutely reproduced from one firing to the other. As an old time potter I feel more comfortable seeing the middle cone down and the next higher just bent at the end of a run, but as has been mentioned many times, total heat work is what determines the glaze results on any run.

I have half a cone difference between the top and bottom of the kiln and it makes little difference for the glazes I use.


WRITE EVERYTHING DOWN! When a kiln load turns out right, try and reproduce conditions as much as you can and don't get to caught up in the some rigid set of "must do".

#64924 Review Of Steven Young Lee Show At Greenwich House, Nyc In Art In America

Posted by Bob Coyle on 22 August 2014 - 08:18 PM

Beautiful work. The "Vases with Eagles" makes an interesting counter point to the other pieces in the show.

#64050 Why Is Our Work Better Than Imported Work?

Posted by Bob Coyle on 06 August 2014 - 02:52 PM

I think this discussion points out very clearly why our work is better than imported work. The discussion mentioned food safe glazes. I'm not sure that the people who sell the cheap imports from China have any idea whether the glazes used are food safe or not. The discussion also touched on ethical considerations, improving knowledge and  technical skill, and also aesthetics. I don't think that these are the primary concerns of the market driven, import industry. As such, there is no desire to change anything, as long as a line is maintaining sales, and what changes that might be made will be pretty well within a range that will sell.


The people in this forum differ greatly in knowledge, skill level, and technique. It is pretty obvious that our work is important to us. We all seem to have in common is a desire that our pieces be worthwhile and reflect our creativity. We strive to get better and try to come closer to producing that piece that exists only in our minds eye. To me, that makes all the difference in the world.

#63752 First Day Of School Clay Activity

Posted by Bob Coyle on 03 August 2014 - 10:40 AM

I'll go with the pres


Give everyone a three inch ball of clay ... including yourself, and start out making a pinch pot as you lecture. Ask the class to listen to what you say about the syllabus, but also to copy what you are doing with the clay.  Every once and a while interrupt your talk to give a brief hint on the pinch pot like, " try to keep the sides of the pot an even thickness" or "Don't pinch too hard or you will punch through the pot".   If you can walk around and give help to individuals. Then after about half an hour. Stop everyone and have them sign the bottoms of their pots and set them to dry. Tell them they have made their first piece of pottery and open a discussion of  how it went.


I have used this as the opening gambit for clay classes I have taught, and for the most part, it worked out well

#63708 Top 20 Potters From Ceramics History

Posted by Bob Coyle on 02 August 2014 - 03:38 PM

Val Cushing, John Hesselberth and Ron Roy Have made a big impact on ceramics in that a good portion of the glazes used out there are derived directly from formulas derived and tested by these people. There is a lot more to ceramics than just making pots. I think the kids need to know about these people also.

#61085 Glazing Textured Pottery

Posted by Bob Coyle on 18 June 2014 - 10:47 AM

Easiest way to get texture and interest is to just dip the pot in glaze, let it dry, and sponge off the high points so that some of the raw clay shows through. You can also accent the high points by sponging on slips and oxides. kind of dab them on after you sponge of the glaze. There are all sorts of combinations of slip, oxides and glazes that can be applied in sequence. Have some fun and experiment around.

#60407 Glaze Making/ Testing Again!

Posted by Bob Coyle on 09 June 2014 - 06:59 PM

The problem with glaze software is that it might get you close to what you are looking for but it probably won't get you there. You said you want six basic glazes but that is too many. start out very specific as to what your first glaze should look like and then pick an already existing glaze that (supposedly) gives you what you want at cone 6 Then, keep tweaking this glaze ONE COMPONENT AT A TIME as everyone has already stressed. till it starts to look like what you want. Make sure that you have plenty of each material you use. Don't buy 1/4 pound of rutile for your tests and then run out and have to buy from possibly a new batch for your production glazes. Variation in materials can negate all your hard earned progress.

When you get the first glaze to your satisfaction... move on to the next.


Every time you run a glaze test that doesn't work out... ask for help here or over on http://cone6pots.ning.com/   There is at least a thousand years of expertise in glaze development between these two sites.


Don't get discouraged. stay focused on specifics. there is no single answer as to how to develop a glaze. If you are really going to do this... WRITE EVERYTHING DOWN.


And what is really cool, is that sometimes you do an adjustment but it doesn't look like what you wanted in the first place but it is absolutely beautiful in it's own right.  Now you have another glaze that you can use.