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Firing At Cone 05 Instead Of 06


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Hi Folks, 

 

I recently asked a question about my crazing problem using Duncan Envision Glazes. I was advised to try firing at Cone 05 instead of my usual 06 and then slow down the cooling. Unfortunately I have always fired at Cone 06 for my bisque firing and glaze firing and it is only recently I have had the crazing issue. My worry is how the things in the kiln will react. Will I get any warping? Cracking? Or other problems with the bisque? Problems with the glaze?

I tend to use Mayco Stroke and Coat, which says fire to Cone 06 on the bottles and Duncan Envision together on earthenware clay.

 

Many thanks in advance, Kevin.

 

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Guest JBaymore

I've said this one a million times on the forums............ One of the things that you can never get around in studio ceramics is the need to "test, test, test". There are so many variables involved in any given situation that the only way to know for certain is to try it (and try it repeatedly to verify results).

 

best,

 

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

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Years ago, I was doing low fire (^06) earthen ware. We were using Amaco glazes at the time. I had always bisqued to ^06, and did then. I had been glaze firing to ^06 also, but found that some of the glazes did not seem to be quite right, and some had some crazing problems. I also noticed that I had a problem with some pin holing on some glazes.  I decided to try different firing cycles, and tested with many witness cones. After all was said and done, I decided to move to ^05, and be cognizant of which glazes needed higher temps and which were in need of cooler ones.  The Amaco glazes used to say 05-06 and I believe that was for ease of labeling as not all of them are 06. Best bet is to become very familiar with your kiln, and with your glazes.

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Many thanks for the replies.

 

I usually fire my bisque and glaze firing together. Will I have any problems if the glaze firing is a higher temperature than the bisque firing? I say this because I have several tiles which I have already bisque fired to Cone 06 and glazed, would it be dangerous to fire these to Cone 05 now?

 

My goal is to eliminate the crazing which I have experienced on my last couple of firings using Duncan Envision glazes and I was advised to try a Cone 05 firing. I currently hold the temperature 998º for 10 minutes, could it be worth holding for longer?

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I used to fire my class kiln , with both greenware and glazed bisqueware together. I don't do this now, if I can avoid it, because it seems that every time I try, something is thicker than it seems, or has an unknown void, which haven't dried, and I end up with bits of bisqueware stuck on the glazed projects.

 

Annnnnnyway, you would not have an issue refiring those tiles. I've refired projects multiple times, to get the glaze to turn out better. I will say, the last firing, a stress crack did appear, so there are limits.

 

In regards to holding, I wouldn't think this would help with crazing, as crazing has more to do with the glaze fit. So instead of holding, you'd be better off slowing the cool down.

The only way to know for sure, is to do what John recommended; test, test, test.

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Ditto on what John just said. I never fired the two firings together in those days. Most glazes at the lower range are sensitive to gasses from the bisqueware. Yellows, reds and oranges in particular. It can also effect the blues to some degree making them a little less clean.

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Hi Kevin,

I probably should have mentioned that I have noticed a slight color change at 05 with the Envisions, they tend to darken. These glazes don't move at all, even at 05, and I haven't had any problems with warping or cracking on either a white talc based body (Laguna #10-T). I used a cooling ramp of 250F to 1500F but I'm still testing to see if I can speed that up and get the same results.

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  • 5 years later...
  • 10 months later...

I am a rookie Potter. I make baby hand and footprint impressions. I have been using Laguna -Miller 110 clay. I have been firing my greenware to cone 6. I also fire my glazed bisque to cone 6 and have been using primarily Duncan Envision. My last fire (glazed bisque) I had 2 of my handprints crack starting at the edge and about 1 inch all the way through. I have an older manual kiln (and it has thus far worked perfectly). My glazed pieces were positioned in the kiln very close to the heating coils. Would that have caused them to crack? I was going to attempt to repair them by using WareRepair then glaze over it and refire. I have reglazed and refired  pieces before when my glaze wasn’t even. It has worked beautifully so far. I have found it’s hard to disguise a crack trying to fix it the “ceramic way” - rather than , for example , filling the hairline crack with gorilla glue then using an extra fine sharpie at just the right color to cover the crack and use a touch of high gloss clear nail polish gel to add back the gloss. Any suggestions?? The cracks are too thin to add crushed bisque mixed with anything. Will the Ware Repair fill in the crack or just melt out?  Thanks

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All of theses products -Marks ware repair or amaco bisque fix all can work-Marks ware reapair is more fluid than all other like products-They all will leave a mark of a different color so glaze need to cove them-They will NOT run out as you mentioned . Testing is the only way to know for sure about color matching-again use glaze over them to cover the non colora match.

I have used them for years and thats the olny way to learn what they do and how they look.

Glue and markers is not a valid way to fix an item  for anyone unless its for yourself.

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