Shortening the Firing Time
While experimenting with firing in more efficient ways I discovered something that can shorten the firing time significantly. It seems that the first phase – in which the binder is expended – does not have to be done in a kiln and can be completed in as little as 10 minutes, with no cooling time between phases.
This can be done with the SpeedFire Cone system, on a camping stove, or on the kitchen stove.
Here is how it works:
Pour a 1″ layer of carbon into a small stainless steel bowl. Place your pieces on top of it without covering them in carbon.
Put the bowl on the burner.
Cover the bowl. You can use the cone from the cone system, or the circular fiber box that is actually a firing box, or a fiber board, or a piece of fiber blanket. If you use the cone, cover it with a fiber board or a fiber blanket.
In each of these lids drill a pencil-size hole. To do this in a fiber board or the fiber box you can use a screwdriver. Just twist it in; the fiber is very soft. With the fiber blanket just stick in a pencil to make the hole.
Here are some photos of the set-up:
This photo was taken inside my studio, but this should be done outdoors.
On the left is the fiber box; on the right is the fiber cone. The pans are flat, but I mostly use simple bowls.
If you do this in the kitchen, the fiber blanket is not recommended. You can protect your stove with aluminum foil.
Turn the flame on to full capacity. After a few minutes you will smell and see the smoke coming out of the holes in the lids. This is the binder burning. I tried to photograph it, but it turns out that smoke and fire are hard to shoot.
After about 10 minutes the smoke will stop. Remove the lid with a glove and peek inside. The pieces should look black.
Pour more carbon into the bowl to cover the pieces and put them in the kiln for the second phase of firing. The whole process takes about 2:30 from beginning to end.
I have just fired a batch of thick pieces. If I had done the first phase in the kiln, I would have had to hold for at least 2 hours. Given that the ramping takes about 30 minutes and the cooling time at least on hour, I saved myself 3:30 hours.
Why not burn the binder with a torch?
I have tried this many times. The pieces were positioned the same way, in a bowl with a 1″ layer of carbon. This works only sometimes. In most cases pieces crack from the direct heat, and the cracks do not necessarily show until after the second phase is over.
Why not do the same thing in a kiln?
I have tried this as well. A kiln takes a long time to ramp. This exposes pieces to oxygen for an extended length of time and most probably causes internal oxidation. That means that when they come out of the kiln after the second phase, they may crumble, but not necessarily because they are not sintered: it’s because they are oxidized.
Why is the fiber cone or box necessary?
Without them, it would take a long time for the pieces to heat up and they might oxidize, just as in a kiln. The fiber cone and box create a hotter chamber, partially shielded from oxygen.
A word about internal oxidation: before the advent of base metal clay, I used copper pipes, rods, and wire (solid, or bare, copper, from plumbing supply stores). I used to wrap them with silver clay (low shrinkage) and fire. Cracks would occur because of the shrinkage of the silver, and I had to repair and re-fire. Nothing in the way that the copper looked showed any sign of oxidation. However, after a few repairs, the copper would crumble in my hands.
This is one of the reasons that I avoid firing copper in open air. Even if it looks fine after firing, you never know what is going on inside. Furthermore, sometimes the copper needs to be re-fired, as in repair, enameling, soldering, or adding silver clay. With each firing the copper oxidizes further and weakens, just like what happened with the solid copper.
September 13th, 2011 at 7:39 pm
Hi Hadar,
This looks like a great time-saving breakthrough. Alas, I have an electric stove, I don’t have a cone firing system or circular boards, etc… Which begs the question, “Can I stay with the kiln system as you already have it until such time I have the alternative set up?”
Thanks,
Melody Pierson
September 13th, 2011 at 7:49 pm
“This photo was taken in my studio, but it should be done outdoors” – love it!
Thanks for sharing your breakthrough. Faster is exciting!! I guess I won’t be packing the camping gear away after all. 🙂
September 13th, 2011 at 7:50 pm
Am I understanding this correctly…I can put the carbon in a stainless steel bowl, top with a fiber board (with a hole in it) and I am good to go on top of a stove? I don’t need the fiber box?
Thanks!
September 13th, 2011 at 7:55 pm
Lauren,
The stove only replaces the first phase of firing. After this you need to fire the second phase in the kiln. Please have a look at the instruction manual.
September 13th, 2011 at 8:17 pm
Hi Hadar, what an intriguing idea! Will it work on an electric kitchen range with a glass cooktop?
September 13th, 2011 at 8:17 pm
I have an electric stove, will this work? Also does this cause a lot of smoke in the kitchen… Enough that the fire alarm will go off? Do I cover the coils on the stove with foil first? Or must I use a gas stove?
To clarify, I’m to drill a hole into my round firing box? Won’t that ruin it for firing the second phase? I’m a bit confused.
I have been firing in the round fiber bowl. Cutting the time down would help.
Thanks for your help.
September 13th, 2011 at 8:21 pm
Hadar,
Thank you for the tip! I will try it! You are the best!
September 13th, 2011 at 8:23 pm
Thanks for the info. I am wondering what you recommend for classes as this seems like a set up that would work at home (the gas stove or outside grill), or is for a few pieces (the cone fire system), but it may not work in a classroom setting. I have been thinking of using your clays when I teach, but I wasn’t sure how to manage the firing schedule during a 3 hour weekly class that is away from my home. This could help solve the issue if I could find a set up that would work at the studio where I teach (on the third floor without an outdoor space).
Any ideas would be welcome.
Thanks,
Mary Ellen
September 13th, 2011 at 8:24 pm
Hi Hadar,
I fired my silver clay on the stove for a year before I got my kiln and it always worked very well. I am always excited to save time so I can’t wait to try it. I have a square fiber board box and I was wondering if I can use it on top of a small ceramic container or is there some reason a stainless container is necessary for the process to work.
Thanks
Cindy
September 13th, 2011 at 8:53 pm
Marla, I haven’t tried an electric stove, so I really don’t know. If you drill a hole in the box you can’t use it as a firing box anymore. You will need another box, or just fire in the bowl.
September 13th, 2011 at 8:56 pm
Margaret, Haven’t tried. I don’t have one. Would you be willing to try?
September 13th, 2011 at 8:58 pm
Cindy,
I think the ceramic container will break from the thermal shock. These bowls are really cheap and you can go on an fire the second phase in them as well.
September 13th, 2011 at 9:02 pm
Mary Ellen,
I would definitely use it in class. You cam do the first phase for one batch on the stove and move it to the kiln for the second phase. Do the first phase for another batch and move it to a second kiln, etc. This is what I am going to do from now on.
September 13th, 2011 at 10:03 pm
I always fire the 1st phase in my kiln, no carbon at all. Go full speed to 475C/887F. The binder burns between 165C/329F and 265C/509F. After the smoke has disappeared I set my timer at 10 minutes so I can be sure all the binder is gone. It all takes about 20 minutes. Handle pieces with care when you replace them in carbon for the second firing phase.
September 14th, 2011 at 12:20 am
Wow! I am travelling at the moment and I brought some clay “just in case”. This means I can fire it in my mum’s quite primitive summer cottage in the Swedish forest. Perfect.
September 14th, 2011 at 12:22 am
This is really great for me as after the 1st phase the pieces will be stable enough to put wrapped up in my suitcase. This way I can do clay wherever I want to! Fantastic.
September 14th, 2011 at 4:26 am
Hadar, you are amazing! I love this!!!
September 14th, 2011 at 4:27 am
Thank You Hadar. I will try that right now. What a wonderful news, if I can cut my firing time….it took so much time to cool down my kiln between phases!
September 14th, 2011 at 4:35 am
I’m just wondering if I can use my No-Flake Firing Foil on the stove? If so, can I just use the lid with the hole punched in it or do I need the fiber board?
September 14th, 2011 at 5:24 am
So would this work on a BBQ grill as well?
Also been wanting to ask where to get those big gloves you use for lifting the hot pans? I’m wanting to fire as I haven’t done any since class.
September 14th, 2011 at 6:48 am
Just in time…ready to fire some pieces today, will try your new method. Thanks so much Hadar.
Regards…
September 14th, 2011 at 7:25 am
Hadar,
Everyone is talking about this method, and not mentioning the “SpeedFire Cone”. Along with the fiber board, stainless bowl, etc. you still need the SpeedFire Cone Bowl, right???
After reading your post I understood, until I read everyones comments and now I don’t.
You need to get the Ceramic speedfire cone, Right???
Virginia
BTW, I appreciate that you are always experimenting on perfecting this art. Thank you!
September 14th, 2011 at 7:27 am
Hadar,
Everyone is talking about this method, and not mentioning the “SpeedFire Cone”. Along with the fiber board, stainless bowl, etc. you still need the SpeedFire Cone Bowl, right???
After reading your post I understood, until I read everyones comments and now I don’t.
SpeedFire Cone needed???
Virginia
BTW, I appreciate that you are always experimenting on perfecting this art. Thank you!
September 14th, 2011 at 7:28 am
Hadar,
Everyone is talking about this method, and not mentioning the “SpeedFire Cone”. Along with the fiber board, stainless bowl, etc. you still need the SpeedFire Cone Bowl, right???
Virginia
BTW, I appreciate that you are always experimenting on perfecting this art. Thank you!
September 14th, 2011 at 7:55 am
Hi Hadar,
This is an amazing breakthrough! Thank you for experimenting and pushing the envelope! I am curious, I know you use stainless steel bowls to hold the pieces and carbon. For those artists who have the stainless steel containers with the lid, can they use a stainless steel lid with a hole in it? Why use the fiber bowl?
September 14th, 2011 at 8:12 am
Hi Hadar,
I can’t do it in the next week or two, but I can try after that.
Margaret
September 14th, 2011 at 8:14 am
Otteline,
That is because you have a kiln that ramps so quickly. My brick kilns take 45 minutes to ramp.
September 14th, 2011 at 8:16 am
Jenny,
Please read the post again. You still need a kiln for the second phase.
September 14th, 2011 at 8:18 am
Jenny, I don’t recommend it. The pieces will be very brittle. However, you can make them and not fire them. Then you can store them in a sandwich bag full of rice and carbon and travel with them.
September 14th, 2011 at 8:23 am
Janet, the steel containers are thick and take a long time to heat. But you can try. The fiber bowl helps create a hotter chamber that is somewhat protected from oxygen.
September 14th, 2011 at 8:25 am
Beckie, you certainly can. However, as a lid I doubt that it will help create a hot chamber and protect pieces from oxygen.
September 14th, 2011 at 8:28 am
Virginia, What I said in the post is that you can use either one: The cone, the bowl, and a fiber board. I would even use a fiber blanket.
September 14th, 2011 at 8:32 am
Karen, I guess you can but I haven’t tried. The gloves are from http://www.slumpys.com. Pretty expensive.
September 14th, 2011 at 8:33 am
Virginia, Not necessarily. You can use a camping stove and a fiber board instead.
September 14th, 2011 at 8:43 am
Melody,
Of course you can.
September 14th, 2011 at 1:15 pm
So there has to be a fiber cone or box on top of the stainless steel bowl, not just a fiber board?
September 14th, 2011 at 1:30 pm
Small country, small….., small kilns! Finaly, such an advantage. LOL!
September 14th, 2011 at 1:40 pm
If so where do you get the fiber cone or box?
September 14th, 2011 at 2:03 pm
This type of fast firing can be used with ALL your metal clays?
September 14th, 2011 at 3:53 pm
Karen, fiver board or blanket work as well.
September 14th, 2011 at 3:54 pm
Karen, Both can be found at PMC Connection and Metal Clay Supply.
September 14th, 2011 at 3:56 pm
Eileen,
Yes, but this is just for the first phase. The second phase requires a kiln.
September 15th, 2011 at 4:34 am
One more question–would the same results be obtained by putting the firing box inside a preheated kiln? The temp would go down when the door is opened, but it would reheat quickly I think, thereby eliminating the lengthy oxygen exposure???? Thanks so much, Hadar, for the wealth of information that you so graciously pass on! 🙂
September 15th, 2011 at 7:39 am
Beckie, Yes you can. When you open the door immediately cover the pieces with carbon and there will be no oxidation.
September 17th, 2011 at 4:49 pm
Hi All,
I really hate to ask this question, but I know this can’t be right. So, instead of Hadar could one of you answer.
A stainless bowl with a fiber board on top just doens’t seem right. I need a chamber to go around the bowl. Maybe I could make a chamber(cone) out of fiber blanket. Put it over the bowl.
Im sorry, but none of her pics have just a stainless bowl with a fiber board on top. No chamber!!!!!! Thanks everyone!
September 19th, 2011 at 5:13 pm
Tried this today. Used a single burner – electric, stainless steel bowl, one inch carbon, fiber blankets – one thick, one thin each with a hole in the center. The thicker blanked was overkill. After the first ten minutes there was smoke and the smell of the binder burning off, but the piece was not black. So I did it again and removed the thicker blanket – for another ten minutes – the pieces turned black on top, but not the sides. Did the second phase and when it was done the piece had a green patina on it. However, when sanded the shine came up – totally unexpected. So I think it worked.
September 20th, 2011 at 8:49 am
Way to go, Georgie! Next time no need to fire twice. If the smoke stops it means that the binder is all gone. Sometimes the pieces are not all black (they may become black when they touch air).
September 20th, 2011 at 9:21 am
Good to know! I’m firing some more today…this is very exciting – cutting edge so to speak.
September 20th, 2011 at 12:10 pm
I did my first firing in 9 years…yes, 9 years since I fired silver! I haven’t used my kiln in that many years, so I never fired any base metals.
I began with rose bronze clay. I used the “new” stove top method for phase 1 (gas stove) and all the pieces turned black. I used a SS dog dish; it turned black too. It seemed to work fine. Then I fired Phase 2 in my old programmable kiln at 1470 degrees for 2 hours. I was very satisfied with the test pieces I made; they looked like they had sintered with no problem. That was my biggest worry since I didn’t know if my kiln would come through for me.
When I took them out, there were still black. Normally, I understand that they will come out with a slight patina or oxidation after firing. Is this because phase 1 was done on my stove? I also fired in my kiln without a lid. It seems that most instructions call for a lid. What is the difference?
Thanks for your feedback. And by the way, I love the rose bronze color. It is rich with a slight coppery color.
Jill
September 20th, 2011 at 12:31 pm
Jill, That’s so nice to hear. I am really glad that this firing method encouraged you to start firing again. The black color after firing is normal and is easy to remove. It happened regardless of the firing method. It would have been the same if you fired the first phase in a kiln. The lid is not necessary and does not make a difference either. I’d love to hear how it works for you in the future.