Refire Test Ring from previous Cone 6 Test to 1000c and Intereting Results

[Jan Wallace]

Recently I opened a discussion here with my first test cone 6 test results and photos. I explained that due to circumstances, I did not do a 'controlled cool'. But, that I planned to do some more of the same tests, with a controlled cool which would enable me to see the variables.

I was bisque firing another load of test rings yesterday and thought that I would put in a few test rings from the previous Cone 6 tests to see if any changes occurred refiring to 1000c. I have been reading a bit about this lately and although it does not make alot of sense to me that changes would occur at this low temp without going up to the maturation temp, I thought what the heck.

I only put a few in, but the results were definately interesting. I had a test ring that was Licorice over C Harris Tenmoku and it came out with a lot more life and some crystals and a little more red, that was definately not there before.

 

The other was Variegated Slate Blue over C Harris Tenmoku and the results here are very interesting. The photo below shows the same test tile before on the left and then the after refiring result on the right.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fired to C6 with no controlled cool on Left - Refired to Cone 06 on Right.

 

Question - Does this mean that if i had done a 'controlled cool' originally I would have achieved results like this? Or, because this is this another variable again, completely different results again. If anyone has anything to contribute, I would appreciate it.

 

 

[George Lewter]

Refiring to bisque tempereature and doing a controlled cooling (with or without holds) during a glaze firing are two different methods of adding some additional heat work to your pots, and they might produce some similar kinds of results, but I would be very suprised to see the same results from the two techniques. There are just too many variables that are not the same. When I say that, I'm referring more to the complex mixing you have achieved here, than to a color, such as iron red that might be achievable by either technique.

[Jan Wallace]

Hi George, yes what you said makes sense. I guess that i am just so surprised to see the mixing that has taken place at this temperature and why mixing like this did not take place when I fired it the first time? I guess I expected that for the glaze to soften and mix like this would have required a higher temperature. All very interesting. Perhaps I should put them all back in a bisque firing and see what happens? Welcome back too. Have missed your input.

[Jeff Poulter]

Hi Jan,

  I know this is an older post, but I have been playing around with this lately.  Mostly Iron Reds, but others as well. Anything with titanium/rutile/iron will change when re-heated.  I have even taken things that have been fired to ^6 & then put in a bisque & then re-fired them back to ^6 & you get different results each time.  Then if you add putting some sort of wash on before you go back to ^6, you really change things up.  Last night I pulled 3 pots out of the shed that each had one of the Abotts iron reds on it(Scoria,Iron Break & Saturated Iron) & in the next firing I will spray them with a wash & re-fire them to ^6(I think I have already put them in a bisque before).  I will also have some test tiles in of the other iron reds that I can come up with.  Will post the results(if they're good!)  jhp

[Lawrence Weathers]

I really would like to see what your results were.

[Norm Stuart]

I refired one of the ^6 nickel zinc-silicate crystalline glaze test tiles I'm working on in a bisque yesterday.  It will be interesting to compare the before and after crystallization.  Since the 1,888 F bisque temperature is just above the top range of 1,850 to 1,800 for zinc silicate formation, I added a 30 minute hold to the bisque to provide enough heat to make the glaze fully fluid.

This weekend I'll be able to fire the adjusted version of these glazes (one frit based and the other raw material based) containing an increased amount of zinc, bringing the total to 25%. 

Much more like this . . . http://cone6pots.ning.com/photo/crystalline-vase-firing-july-2013-5...

 

[Jeff Poulter]

I thought I had posted pictures for this. I'll have to wait until I get to work and look to see where they are and post them. Jhp

[Jeff Poulter]

I had to do some digging, but I found the pics.  These were junker fruit bowls that were in the shed. They had been fired originally with different Abbots Iron Red glazes.  Then they were refired in a bisque & got even more red.  I sprayed a Gertsley/rutile wash & refired to ^6.  Some very interesting iron crystals, but a lot of defects in the glaze as well.  I'll do some more experimenting with it this summer.

[Jeff Poulter]

Some more...

[Norm Stuart]

The purpose of a slow-cool between 1,900F or 1,800F to 1,500 F is to give "minerals" time to crystallize out of the melt. 

Even Cone 10 glazes set-up and crystallize within the same temperature range - but having less flux Cone 10 glazes require higher temperatures to create the initial melt.

Rebisquing essentially gives this process additional time, just so long as the peak bisque temperature doesn't melt the existing crystallization back into the melt. 

Being cooled fast or more slowly may likely affect the structure of the additional crystals formed  -- but you'll definitely get more crystals by spending additional time in the 1,900F to 1,500 F range by rebisquing, as in this test tile I previously shared.

Made using this "macro-crystalline" glaze.  I love it when information starts to fall into place.

100.0%  Macrcrystalline ^6
  32.3%  Silica
  27.9%  Custer Feldspar
  18.9%  Zinc Oxide
    8.7%  Lithium Carbonate
   5.0%  Strontium Carbonate
   3.6%  Dolomite
   2.7%  Bentonite
   0.9%  Rutile

This is a similar frit-based version

109.0%  Macrcrystalline ^6
  52.0%  Ferro Frit 3110
  24.0%  Zinc Oxide
  24.0%  Silica
   2.0%  Lithium Carbonate
   6.0%  Nickel Carbonate
   1.0%  Red Iron Oxide