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Bob Coyle

Member Since 06 Jun 2013
Offline Last Active Yesterday, 02:35 PM

Posts I've Made

In Topic: Guess The Rock.

Yesterday, 02:34 PM

I'll throw in with Paul and say a granite of some sort.

In Topic: Brushing Glaze Smoothly

23 March 2015 - 10:39 AM

Brushing on glaze does take practice. I brush all of my glazes and have great difficulty in teaching the technique in class. I use a four section Sumi brush and try to FLOW the glaze off of the brush instead of painting it on. By flow I mean never let the brush starve out and go dry. This means loading it up fully till it almost drips and immediately brushing it on the piece till the brush starts to run out of glaze. You need to go fast and keep a wet edge. you can be a little sloppy and come back and brush over the runs and drips later.


I am usually able to to keep the whole piece moist enough to cover it with a full coat before it dries. I can then FLOW another coat over the first and even out the rough spots. The key is to keep the brush totally saturated with glaze and  go fast enough so that you keep a wet edge between brush strokes. The big mistake people make is brushing on too thin. That is why four coats are required to do the job. I never use more than one thick coat and a second touch up on the thin areas. I tell my students to put it on till it looks way to thick, and then it is about right.


I formulate my own glazes and keep them at about 60% solids. The thicker the better for brushing. I add 1% brushing medium (CMC + perservative) to help stick it to the pot and smooth the brushing.  I weigh out the brushing medium and add just enough alcohol to get it so it is soluble, and swishes around on the bottom of the cup I use. I then quickly add this to the water I use for the glaze and wash the cup and water back and forth . I find this prevents the gum from clumping when the water hits it, and I don't need to use heat or high speed mixers to get it dispersed through the glaze mix.


I try to mask parts of a piece I don't want to glaze and just slop it on rather than use small brushes around tight areas. I use latex masking that pulls off and seldom require touch up around the masked areas.


As Cilia said, the glaze tends to level in firing, and if I have applied it heavy enough I don't get brush marks.

In Topic: Help! Nichrome Wire Leaving Green Stains On White Stoneware

20 March 2015 - 04:21 PM

Never ran into the problem of a green stain above the wire. It is always black where the wire touches of course. I guess you need to try a different wire batch.

In Topic: Help! Nichrome Wire Leaving Green Stains On White Stoneware

19 March 2015 - 10:29 AM

Sure sounds like volatile impurities coming off the wire.  Is it worse with new wire than old? Lubricants are used when drawing wire Molybdenum disulphide is commonly used and may adhere to the surface of new wire if the wire was not cleaned thoroughly in manufacture. I don't know what color Molybdenum would impart to a glaze. If this is a surface contamination problem, then it should go away with further firings. Old wires should be better than new ones. If it is contamination in the wire itself ( probably most wire you get now is made in China and their quality control sucks)  then there is not much you can do except try a different batch of wire.

In Topic: Which Connector Option For A Type K Thermocouple?

08 March 2015 - 07:49 PM

Either will do. depends on what kind of connecion you have to connect to on your controller