Instruction Manual and Pre-firing

The Instruction Manual for Hadar’s clay is now updated and marked May 15, 2013.

Besides adding instructions for firing Smart Bronze, changes have been introduced throughout the Instruction Manual. I recommend reading it through when you get a chance, since it may shed some light on your personal experience.

I would like to share with you my experimentation with pre-firing.

First, not all clays require pre-firing. White Bronze, Smart Bronze (up to a certain thickness) and Low-shrinkage Steel XT do not require pre-firing. Steel, decorated with copper and/or Bronze XT, also does not require pre-firing.

Doors

White Bronze

Smart Bronze with Aquamarine

Smart Bronze

Pentagon

Low-Shrinkage Steel XT

LS Steel XT + copper/Bronze XT Overlays

Low-Shrinkage Steel XT with overlays of copper and Bronze XT

Copper and the rest of the bronzes do require pre-firing. Firing longer hours and/or ramping slower has never worked for me. Recently I have done some more experiments with pre-firing in the kiln instead of on the stove-top. Here is what I did:

Brick top-loader kiln

I placed a bowl inside the kiln with copper and bronze pieces resting on top of carbon. Set the kiln to mid-fire schedule.

In the kiln

In the kiln, set to mid-fire schedule

As the kiln reached 500°F I opened the lid to check on the pieces. I kept checking every 100°F. At 800°F pieces started to smoke and turn black.

Smoking

Smoking

Getting black

Getting black

At 1000°F the smoke was gone and the pieces were all black. I carefully turned the pieces over with a spoon to see if they are black on the other side.

Turning over

Turning over with a spoon

The other side still not black

The other side still not black

This one too

This one too

They were not, but they turned black within seconds. I covered them with carbon, closed the door, and let the kiln complete its cycle. Worked great. 2:45 minutes from beginning to end. If the pre-firing is done on a stove-top, this is the time it takes for the second phase alone. So firing this way is shorter and easier than on a stove top.

Covering with carbon

Covering with carbon

If you happen to walk away while the kiln is ramping and come back after it reached 100°F, no problem. Pieces are probably all smoked up and ready for more carbon. Oxidation will not happen if it’s under 1:00 hour, and even if it does, it will be reversed while the pieces are fired inside carbon.

Turning the pieces over is a good idea. Also, it doesn’t matter if the vent hole is open or closed.

Muffle, front-loader kiln

I tried the same thing in a muffle kiln. Surprisingly, the pieces did not show a sign of smoke until the kiln reached 1200°F. At this point the carbon was already on fire. Since it was a front loader, I had to take the bowl out of the kiln to cover the pieces with carbon, which was awkward at this high temperature. And after the second phase, the pieces were not sintered.

I am guessing the reason is the fast ramp of this type of kiln. The chamber got hot, the outside of the pieces got warm, but the inside needed more time. So slowing the ramp may be the answer.

But then I found out something else. I know that firing twice always works, so I tried it again, but with less time. I fired the pieces in carbon at 1510°F for 1:00 hour. It took 1:20 minutes. Took the bowl out of the kiln and cooled the bowl and the kiln under 100°F. Put it back for another hour, and it worked. Another 1:20 hours, plus cooling time. A little longer, but less messy and more successful.

In fact, the easiest way for me to fire in a front loader was to fire 1:00 hour before I went to sleep. In the morning the kiln was cold so it wasn’t necessary to take the bowl out. Didn’t even open the kiln. Just fired one more hour.


46 Responses to “Instruction Manual and Pre-firing”

  • Linda Reboh Says:

    Hadar, I’m confused. you said in the morning you didn’t even have to open the door. Didn’t you have to put carbon on top of the pre-fired pieces or did you prefire them with the carbon on top already?

  • Ro Germaine Says:

    Well,I just fired some stuff today and I am excited to see what I got…kind of like my birthday every time…Thanks, I’ll read it and see what I can learn from it.

  • Ro Germaine Says:

    I have a muffle and you are right, I do the pre fire in it and it ramps quickly, perhaps a slower ramp, is my thought for the pre-fire part. I’ll do the 1 hr before bed and then do the second in the AM. Thank you.

  • Ro Germaine Says:

    Will there be an update for the firing cheat sheet? I love that sheet;->

  • Susan Weirather Says:

    For anyone living at a high altitude (over 7,500 feet), I have found it best to do the 1st phase on a camp stove, making sure your pieces get as much oxygen as possible. I start with a fire blanket covering the pan and once the pieces start smoking, remove the blanket and allow the pieces to remain with heat on them for at least 5 minutes after they have turned black. I am able to take the pan directly to the kiln and have had great success with pieces sintering completely. Not many have to deal with this scenario, but I’m sure there have been some individuals who have given up and walked away from metal clay because of sintering problems.

  • Amie Says:

    I’m a newbie with your clays and not totally sure I understand your instruction for prefiring in a muffle kiln. I have done a successful firing of brilliant bronze using a campstove for the prefire; are you recommending using the kiln for this now over the campstove? Thanks!

  • Pat Roach Says:

    Thanks for all your experimentation and sharing. This process will be interesting to try.
    For the muffle kiln, do the instructions on page 11 of the manual need to be adjusted to reflect your final experiment? Am I right in saying that for the muffle kiln you ramp to 1510 -hold for an hour, then let the kiln cool down to 100 degrees or less (door closed) and then ramp to 1510 and hold for one hour.

  • Hadar Jacobson Says:

    Amie, For a muffle kiln I would recommend either stove-top firing or firing twice, as suggested in the posting.

  • Hadar Jacobson Says:

    Pat, It is almost correct. You can let it cool down either inside or outside the kiln. As to the manual, you can still do the stove-top pre-firing if you prefer it.

  • Thalia Says:

    Thank you for this valuable update—&, as someone living at a very very high altitude, I was also grateful for Susan’s comment, above. I know that you, Hadar, have mentioned this issue from time to time—& this may not be the appropriate forum to discuss this—but perhaps, if Susan has any other “tips” to offer on high altitude firing, I know that I, for one, would be extremely grateful for them. Thanks!

  • Janice Says:

    How can I tell if my kiln is a muffle or brick? It’s a front loader, made by evenheat and sold as a PMC kiln – before we had anything other than silver to work with.

  • Ann Huckaba Says:

    I want to be sure I understand. When the top loader kiln reached 1000°, pieces turned black, you turned them over and covered them with carbon (no lid on the firing vessel) shut the kiln lid and completed the phase 1 firing cycle; or, did you then switch to the phase 2 firing temperature and complete the phase 2 cycle? Thanks for your help.

  • Hadar Jacobson Says:

    Janice, if you don’t see the heating elements, just white walls, then it’s a muffle kiln.

  • Hadar Jacobson Says:

    Ann, I set it from the beginning to phase 2. When I open the kiln at 1000 to make sure the binder is gone, the temperature drops, but when I close it again it quickly goes up again straight to the goal temperature.

  • Linda Says:

    Hadar – thank you so much for this information! I’m at a higher elevation and had no idea to consider firing things differently. I appreciate the time you took to revise the manual. Thanks again!

  • Gayle Dowell Says:

    I’ve always used a really slow ramp and I’ve always had to prefire my copper, bronze and even white bronze for it to sinter properly. I’m not sure why, but the faster firing has never worked for me. I may try again using this method, because I hate that it takes all day to fire using a slow ramp.

  • Kathryn Says:

    When you say smart bronze doesn’t require pre-fire, does this mean to cover the pieces with carbon and fire to 1470 and hold for 2 hours. Or, is is held just for one. I have a muffle kiln. I’m confused, as usual.:( Blessings,

  • Hadar Jacobson Says:

    Kathryn, Yes, for two hours.

  • Kathryn Says:

    What is your assessment of a problem I have with a recent firing: Front of pieces perfect, back some noticeable surface cracks. What happened, do you think? (Cracks do not go through to the otherside.)This was brilliant bronze. Thanks for your wisdom.

  • Kerri Says:

    For some reason I’m having trouble burning off the binder in the Smart Bronze clay. I have a muffle kiln and fired for two hours at 1470 degrees F (ramp at 1400 degrees F). I have tried twice using carbon from two different sources. Both test pieces were 5 cards thick. After firing one test piece was very brittle and the other bent a little but broke fairly easily. Although I should be able to correct this problem by pre-firing I am very curious why the binder is not burning off for a piece only 5 cards thick. Could it be the carbon? Or, maybe change the ramp speed? Thanks so much!

  • Janet Says:

    Hi Hadar,
    I too am having probems with tne Smart Bronze. I fired three pieces. Two approximately 2in in diameter and round. One 6 cards other approx. 8 cards thick. One flat the other a dropped flowing fold like some of your pictures. The tnird piece smaller oval 4 cards thick no bail. Other with bail. Ramped and fired as per manual instructions. All previous firings have shown the tempersture pretty true to program. Used a square pan all tnree pieces at back of pan, larger two closest to backside third just in front of others. Carbon appox. 1/2 to 3/4 on bottom same on top. Both larger pieces split down tne middle. One half completely diintergrating other half in tact but only top and bottom sintered and broke and sort of crumbled in my hand. Smaller thinner piece seems from first sanding to have sintered. But short of bending it, i don’t know. Think I will just refire to be sure. Before I fire my next batch what do you think might be the problem? I had used this carbon once before for a steel firing. Thanks for any input.

  • Janet Says:

    Sorry Hadar, but forgot to mention I have a muffle kiln and did not cover the firing box with a lid.
    Thanks

  • Kerri Says:

    Hadar, after thinking about what you have said here (the blog and updated manual) and looking at all of my notes about my experience with your other metal clays I have a new question. Is the binder different in the Brilliant Bronze and Smart Bronze than in the White Bronze and Traditional Bronze (or others)? I have even pre-fired the Traditional Bronze in carbon with the lid almost all the way on in a ceramic firing container. After the second phase of firing everything was sintered and strong. At first I thought it was a change in my firing container (ceramic to steel pan) but I checked my notes. The first time I had any trouble burning off the binders with any of the clays was when I tried the Brilliant Bronze for the first time. I will be trying more Smart Bronze again very soon. I think I need to do a better job making sure the binder is burning away before proceeding. Thanks.

  • Hadar Jacobson Says:

    Kathryn, Are you firing in a muffle kiln? The temperature is much lower at the front.

  • Hadar Jacobson Says:

    Kerri, It could be the carbon. And the ramp time should be at least 1 hour.

  • Kathryn Knoll Says:

    Thank you for all your incredible attention to our learning process. I have a muffle kiln. Here is what I found from my experience so far: When I started firing my pieces I did not notice the part about doing the pre-fire with the pieces resting in the carbon, but uncovered. So, I did several successful firings covering pre-fire pieces with carbon. Firing, after cool down covering with more carbon and then doing the second firing. It was only after I started doing the pre-fire with uncovered pieces sitting in carbon that I got the surface cracks. So, I returned to my initial method of covering the pieces in carbon for pre-fire. Then after cool down covering with more carbon and doing the second firing. The binder seems to burn out fine with covering. Sintering takes place in the second firing fine. I’m sticking with my method, for now. I can do about 3 firings per day. This is a good pace for me. I have not done too much yet with the smart bronze but, will continue with the method that works for me with that. I do a pre-fire with white bronze also as if it were one of the other clays that require pre- fires. Any insights you have to share on this, I welcome.

  • Kerri Says:

    Hadar, thanks so much for your advice. I have tried once again and now I think I can get it right next time now that I have learned more about my two different carbon types and firing containers. I over fired this time but the binder must have burned off since the test piece was much reduced in size and was not brittle (used the stove and then in carbon in the kiln.) I have had trouble with surface cracks too when burning off the binder on top of the carbon in the kiln (brilliant bronze.) I am curious whether this is due to the release of moisture from the carbon. Only the more flat pieces had this problem on the under side. My bead caps with holes (like a steam vent) and narrow twigs looked great. I can’t believe how much water the carbon absorbs even in a day or two in a ziplock bag.

  • Hadar Jacobson Says:

    Kathryn, the second firing a;ways does it. I think you should stick to what works best for you.

  • Hadar Jacobson Says:

    Kerri, It didn’t occur to me that it may have been moisture. I, too, noticed that flat pieces suffer more from cracking on stove top. I think hollow and curved pieces are much stronger in nature.

  • Carolyn Says:

    Hadar, I am also running test firings per your recommendations in the Instruction manual. I have a front loaded muffle kiln and am combining Quick Fire Copper and Bronze clays. I also have questions about the Pre-firing stage. Is it sufficient to let the kiln heat up to 1200 degrees and not hold, or are you recommending holding for a period of time? At one time, there was the recommendation to fire between 30min – 1 hr, depending on number of pieces. Also, once pieces have been fired to burn off the binder, it sounds like there is no need to cool the metal and kiln to continue onto Phase 2. Is this correct? I ditto everyone elses’ comments with great appreciation for your dedication to teaching. It’s inspiring.

  • Hadar Jacobson Says:

    Carolyn, I recommend either pre-firing on a stove top and continue immediately to phase 2, or fire twice, with cooling between firings.

  • Joette Monson Says:

    Hadar – I’m having major trouble with the Smart Bronze clay. I have a muffle kiln and fired for two hours at 1470 degrees F (ramp at 1400 degrees F). The pieces were burnt to death – disintegrating when I tried to pick them up. I even tried firing for only one hour and got the same result (tho not quite as severe). I took my kiln in and had it tested – it’s fairly new and is firing properly. How could be results be so off with this new clay? I have had many succesful firings with your other clays. I am obvisouly doing something horribly wrong and I don’t know what to try next. Any guidance you could give me would be greatly appreciated. It’s keeping me up night!

  • Sylvia Says:

    Hi Hadar,

    I’ve tried your the firing schedule without pre-firing for white bronze and the pieces did not sinter. I had about 20g in my muffle kiln for 1.5 hours. Should I raise the temperature next time or fire them for 2 hours instead of 1.5 hours? I’m trying to make key chains (fobs) with the white bronze. Is white bronze strong enough for this use? Thank you.

  • Hadar Jacobson Says:

    Joette, Was there a lot of ash at the top of the carbon after the firing ended?

  • Hadar Jacobson Says:

    Sylvia, White Bronze is not recommended as a structural part because it’s somewhat brittle. Instead, you can make a piece out of bronze, fire it, then paint it with a few layers of White Bronze, and fire again.

  • Joette Monson Says:

    Hadar — There was probably a little more ash than usual. I can email you a picture. Maybe I need a different kind of carbon? If so, do you have a supplier/brand you recommend for use with the Smart Bronze? Appreciate your insight as I am anxious to start experimenting again. Thank you.

  • Joette Monson Says:

    I am using the coconut based acid washed carbon from Rio Grande.

  • Hadar Jacobson Says:

    Joette, Last time I tried this carbon it required raising the temperature bu 40 degrees. Try the coconut carbon from PMCConnection.

  • Kerri Says:

    Hadar,
    I finally had success with smart bronze (no more crumbly black pieces)! Since I struggled burning the binder out I decided to try something different (and I really didn’t want to open the kiln and flip the pieces over because I have a front loading muffle kiln). I tried using the steel net from Metal Clay Supply to burn the binder out. I think it works well because the pieces heat/burn the binder out evenly. When the pieces sit on a shelf or on carbon maybe they are heating unevenly and then crack. I don’t even know whether carbon is needed at all for the burnout. In fact during my first try with the net the two pieces that were too close to the carbon below still had binder in them on the bottom side (I used the stove to finish burning it out). For my second try (see the photo on my flickr site-the page that I linked to this comment) I made sure the carbon was at least 1/4 inch below the net. So far nothing has cracked. I have even made thin flat earring that warped during burn-out but did not crack. Although I used the steel pan to burn out the binder I used my ceramic container for the second phase. I fired my test piece at 1445ºF for 2 hours in Magic Carbon (if I had used a different carbon I would not have reduced the temp.). After firing I could see that it shrunk about the right amount and I could bend it into a U shape with no cracking or breaking!

  • Hadar Jacobson Says:

    Kerri, Are you sure the pieces don’t pick up the texture of the screen?

  • Kerri Says:

    I checked the back of all of the pieces and they were completely black and there were no marks. I moved them into carbon only (no screen) for phase two.

  • Hadar Jacobson Says:

    How do you move them when they are hot?

  • Kerri Says:

    I waited until they were cool before checking the back sides and transferring them from the screen/steel firing container to the ceramic firing container. I noticed that smoke came out of the kiln vent at 550ºF. I didn’t look inside the kiln but do you think that when the binder burns in air (not in or on the carbon) that we can reduce the temperature? I burned the binder out at 1100ºF for 45 minutes. The ramp speed for both the binder burn out and phase two was 1400 (do you think that maybe this could be modified too?)

  • Hadar Jacobson Says:

    Kerri, no, that’s a good speed.

  • Kerri Says:

    Thanks Hadar, I will continue using that speed.

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