Shortening the Wait Time Between Firing Phases

The waiting time between the two firing phases can be shortened to less that half an hour. I took many photos of the process to make it as clear as possible, but the whole process, including taking the photos, took 30 minutes.

The kiln finished the first phase. Hold time was 1:00 hour because the pieces were large. Temperature was 1000°F/528°C (top loader). I opened the kiln right away.

A mixing bowl was waiting, empty.

I placed a sieve inside it.

I filled the bowl halfway with cold carbon.

Wearing heat protective gloves, I took the firing box out of the kiln.

Again, wearing heat protective glove, I started pouring the content of the box slowly into the sieve.

The pieces fell onto the soft carbon, which protected them from breaking.

Once the firing box was empty, I held the sieve and slowly lifted it out of the bowl.

I set the sieve aside to cool down the pieces. The temperature outside was about 50°F (10°C). After 5-10 minutes the pieces were cold to the touch.

I re-filled the box with cold carbon.

I carefully picked the pieces out of the sieve with my fingers and placed them in the cold carbon. (On another occasion, I saw a crack on one of the pieces. I was able to mend it carefully without breaking the piece).

I put back the rest of the pieces, then poured cold carbon on top of them.

Now all I had to wait for was for the kiln to cool down to about 250°F/120°C. I put the box back in the kiln and went on to the second phase. As I said, about 30 minutes from beginning to end, including all the pauses to take pictures.


14 Responses to “Shortening the Wait Time Between Firing Phases”

  • virginia sajan Says:

    thank you. that was a very detailed explanation. i mostly do enamel but i think i must finally try this.

    also, i like your work quite a bit. this bracelet was particularly enchanting.

    thanks,
    Virginia Sajan

  • ann schneider Says:

    Thank you so much! This is great. I know you never sleep.
    a

  • Sarah Triton Says:

    I agree with the previous poster; Do you EVER sleep? BTW, what’s holding the corners of your fiber cloth box together? Staples?

  • Hadar Jacobson Says:

    Sarah,

    It’s T-pins from fabric and office supplies.

  • janice abarbanel Says:

    Hadar, are you using the high temperature wire rigged up as a handle to remove your work from the kiln or are you just using gloves? I’ll be switching to these fiber blankets as soon as I can find a local supplier. Thank you!

  • Adriana Says:

    Dear Hadar, where can I order the fiber cloth? By you? Thank you for share your experienceses, it helps a lot, especially people as me, who leave in Europe and can not take part in your classes.

  • Mary Says:

    Thank Hadar…do you prefer woven ceramic cloth or fiber blanket for making the box? and is the woven ceramic cloth box made with two thicknesses? Does the box rest on a kiln shelf, raised 2 inches in the kiln? And waiting for the kiln to cool to only 250 degrees rather than room temperature works, right? I see that the firing cloth Wholelottawhimsey sells goes only to 1650 degrees so what do you use when firing regular steel clay? Are those Kevlar gloves you have on? Thanks and sorry for all the questions….

  • Hadar Jacobson Says:

    Janice,

    I use the gloves. I suspect the wire would cut through the fiber blanket.

  • Hadar Jacobson Says:

    Adriana,

    I buy the cloth from Glass suppliers. They are currently out of stock, and in any case, this particular supplier charges a lot for minimum order and shipping. I suggest that you find a local supplier for fiber blankets.

  • Hadar Jacobson Says:

    Mary,

    I do prefer it but only for safety reasons. It does not have to be 2 thicknesses. It rest on 5 posts rather than shelf for better heat flow. 250F is enough, yes. My cloth is not the same as the one you mentioned. And I don’t know what brand my gloves are, but they are purchased from glass supplier and suppose to withstand very high temperature.

  • Nancy Conrad Says:

    Although this may be more appropriate on the previous posting by Hadar on firing issues, I’ve been slow!
    I’m writing this to hopefully be of help to others regarding my firing results & conclusions. After taking Hadar’s class in Amado, AZ (which was, of course, a wonderful 2 days!), I came home & did 11 firings over 5 days in prep. for a class I taught the following weekend. I did an additional 7 firings during & immediately following the class. All of the firings were with Hadar’s copper & bronze clay.
    I live at 6500 ft & have a Paragon Caldera kiln with an 8″ chamber, top loading. I used a 2nd identical kiln and also a small (4.5″ chamber) Paragon front loading kiln.
    The firing box I built out of kiln bricks & fireplace cement (rated to 2000 degrees) worked well to begin with, but the cement loosened after only a few firings & the box feel apart when getting it out of the kiln hot. The fiber blanket boxes work well. The PMC connection round fiber box was also fine & easier than the blanket box to get out of the kiln while hot since it is smaller & has rigid sides. The only problem I have with this box is that it doesn’t hold as much. Here are my other conclusions
    * always do 2 phases with cooling completely in between the phases, 1st phase ok to do overnight, but not the 2nd phase
    * fire with the firing container completely open (no cover on top) & kiln vented
    * take the box out of the kiln ASAP after the first phase to cool (if you are in a hurry to move on), as well as after the 2nd phase to cool
    * dump the box after the 2nd firing into metal strainer if you want, but it’s also ok to just let it cool outside in the shade
    The pieces sintered well in the Caldera kilns & didn’t alloy or melt at 1460 degrees, held 2 hrs. at the 2nd phase (1000 held 1 hr at 1st phase). Same schedule for both blanket box & rigid side round fiber box. The small kiln fired ok at 1450, but there was a greater temperature variation & a few pieces alloyed or didn’t sinter.
    A large bronze mask (3″ x 4″, 80 grams) also came out great!–I slowed down the 1st phase & held it 2 hours due to the size & thickness.

    Now I am eager to try Hadar’s new dumping straining technique she shows on this post!
    Thanks Hadar for all the great info you share so liberally!

  • Bonnie Says:

    Thanks again Hadar for keeping me and many others up to date with your latest research. Your knowledge and guidance is a great inspiration to me! …but what am I doing wrong? My copper and bronze designs continue to come out of my front loader kiln with cracks throughout the pieces. Please let me know what I must do in order to correct this problem. Thank you!

  • Hadar Jacobson Says:

    Bonnie,

    It can be either not enough carbon or the wrong kind. It is also possible that your kiln is overheating. Try to lower the temperature. In any case, you can repair this by pressing clay in the cracks and re-fire.

  • Linda Smith Bundy Says:

    Hi Hadar
    I have been trying to find the firing schedule for Original Bronze. I have tried every one that I could find that has been published. I came to the conclusion that there needed to be a two phase firing. I am still using a pan-the smaller one. I have been working on the temperature increasing it in slow amounts from firing to firing. It turns out in my kiln the best temperature is around 1580. Any hotter then there are blisters. If the temp is under 1560, then the clay does not sinter. I kept lowering my temp in the beginning as is often recommended. When what I really needed to do was increase the temp. So the last two firings have come out with a good sinter. I will be tumbling this weekend to see how that goes.

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