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sbesse

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  1. Thank you John The mechanism of traditional oil spot (which is high fire, not Cone 6 range) is based on the instability of the red iron oxide molecule above about 2250 F. Orton Cone 6, if you are using the large cones, is going to barely reach that temperature. The slower you fire the LOWER the end point temperature will be at any given cone. (Remember, cones measure heat work, not tmperature.) At 270F per hour rise, Cone 6 end-point is 2266-ish F. So it will start to break the bonds.... but it is "close". I'd suggest that you fire the last about 200 F of the up cycle at a fast rate.........like 270 to 300 F per hour (if your kiln will do it). That will make sure that you end at a "hot" remperature for the Cone 6 dropping. Then play with the soak period at the end to allow time for the evolution of the oxygen gas to bubble out of the underlying glaze layer and bring the "spots" to the surface. It will require some testing for you to see how long a soak gives you what type/size of spots. best, .....................john
  2. Thank you - I will try a couple of few different options when I fire next time Shelley Years ago, I was using an oil spot black that was a brown on all of my test tiles. I did a mixed firing with the kids, and so everything was the same. One day however, I mixed in too much water, and the glaze was too thin in the 5 gal. bucket. I told the kids to use a double dip, and not to leave for the full count(we had discussed double dipping in demonstrations). When the kiln was opened with 3 pots in it with the Oil Spot black-two had significant black/brown spotting, and a third was basically all brown. In the future I place pots on the shelf area where the first two were, and never in other areas-problems solved. You might try it.
  3. Thank you! - if I try it I will post my results Shelley
  4. Would you recommend a slower firing? I use a Skutt Kiln (I just use the preset computer setting - usually medium speed)
  5. Hi Marcia, thanks for your reply/questions I fired on medium speed (my Skuttt kiln is computer controlled so I use the medium speed setting - I don't know what the firing schedule is) Oxidation Firing Laguna Speckled Buff (Cone 6) Today I added 2% additional copper carbonate to the glaze a did a couple of test tiles altering the thickness of the glaze - we will see what happens. Any insight is appreciated - thanks Shelley
  6. I recently attemped to make and fire a Cone 6 Oil spot glaze (medium speed, cone 6). Clay is speckled buff. The glazed turned brown with no oil spots. Hydrometer reading was around 53%. I held the pot in the glaze for a 3 count. I am wondering if there is anything I can do with the glaze to get better results - I thought about adding an additional 2% copper carbonate. Does the thickness of the glaze matter? Would I get a different result if I fired to Cone 5? or on a slow speed firing? I have listed the recipe below. Does anyone have a good oil spot glaze recipe they would be willing to share? Hal’s Oil Spot Glaze C5-6 Silica 19.5% Bone Ash 9% Iron Oxide 9.7% Kaolin (EPK) 5.7% Nepheline synite 44% Talc 5.7% Whiting 6.5% Increased oil spots add: Cobalt .15% Copper Carbonate .5% Rutile 5% Tin 1% thank you!
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