bisque firing in a pit kiln

[Markalanb]

I am new to ceramic work and want to be able to do all the firing in a pit or other backyard type of home made kiln.  I am trying to avoid using gas or electric power source.  I am looking for advice on how to do a bisque fire and glaze fire with those limitations.

 

[Mark C.]

solar kiln? wood fire kilns?

[neilestrick]

A pit heats up very quickly and unevenly. You'll have a high loss rate firing greenware in it. It also won't get hot enough or fire clean enough for bisque. Nor will it work for glazes. You need an actual kiln of some sort in order to bisque and glaze fire, not just a pit. That doesn't mean the kiln has to be anything fancy or highly engineered- a primitive design can work. I wouldn't worry about bisque firing if you go that route, though. Single firing would be much easier in that situation. A simple tube kiln fired with wood would do the trick. You can build a small one out of homemade castable material. You'll want to check with your local building codes to see if it's allowed where you live, because it is essentially the same as open burning. There will be flames and smoke.

[Markalanb]

2 hours ago, neilestrick said:

Thank you for your response Neil.  It is truly appreciated.  I am trying to avoid an electric kiln due to the high cost of just keeping the house cool during the summer months here.  What about a gas kiln.  I am just returning to ceramic work after a 40 year absence.  So I have some experience. mostly while a student at the Art Inst of Chicago.  But I never had to actually know much about the firing process.  I did install an electric kiln once at Arcosanti.  

Anyway, I am open to any suggestions or advice as I find my way through the maze of home grown ceramics.

 

[liambesaw]

I used an Ian Gregory style flat pack kiln for a year or so, it worked pretty good, fires on propane with a weed burner.

http://www.ian-gregory.co.uk/kilns.html

[neilestrick]

You may be able to get away with a small round gas kiln like the ones Olympic sells, or even build your own out of an old electric kiln, but they are imperfect kilns. They tend to be very finicky and fire unevenly. There was a recent post about them HERE that has some good solutions to making them work. Again, check with local codes.

Any chance you can set up an electric kiln in the garage where the heat won't be an issue?

 

[Markalanb]

I meant the heat here in Arizona.  Costs about $350 a month to cool the house to about 76F.  Add a electric kiln I bet even doing 1 or 2 firings a month would double that.

[liambesaw]

10 minutes ago, Markalanb said:

I meant the heat here in Arizona.  Costs about $350 a month to cool the house to about 76F.  Add a electric kiln I bet even doing 1 or 2 firings a month would double that.

No, doesn't cost that much to fire a kiln.  Mine costs me less than 10 dollars a firing.  Propane was about 20 dollars a firing.

[Min]

@Markalanb, what is your kilowatt per hour rate? It's fairly straight forward to do the math to get an estimate on firing costs.  Just take the formula below and plunk in your electric rate and you'll get an idea of cost to fire a kiln. Example below is for a 7 cubic foot Bailey kiln, it's a popular size as they can run off a 60amp breaker. There is also the home insurance aspect to look at. There is no way I could get insurance if I had a gas kiln on my property, it was hard enough finding a company that would insure me with my electric kilns.

From Bailey: 

"First, find out how many kilowatts your kiln uses. You can find your kilns KW listed on the kiln's electrical control box and/or in your kiln manual. Our 7 cubic foot, cone ten electric kiln: TL-2327-10 uses 11.5 KW.

We know that the elements will probably not be engaging at full 100% power at all times. In a typical bisque firing we can divide the firing time into quarters to represent the power engaging at 25%, 50% 75%, and 100%. So, if you applied that to our TL-2327-10 model (11.5 KW), and we assume you are firing a "Slow Bisque" with a Bartlett Controller (13.5 hours to cone 04) you would calculate as follows:

25% of 13.5 hours = 3.375 hours (13.5 hrs. divided by 4)

25% of 11.5 kilowatts = 2.875 (11.5 KWs divided by 4)

3.375 hrs (25% time) x 2.875 KW (25% KWs) = 9.7

3.375 hrs (25% time) x 5.75 KW (50% KWs) = 19.4

3.375 hrs (25% time) x 8.6 KW (75% KWs)   = 29.1

3.375 hrs (25% time) x 11.5 KW (100%KWs)=38.81

Now, we add those totals to get a total of Kilowatt Hours : 97.01 Kilowatt Hours

97.01 x (rate that you pay per KWH as per your monthly invoice)= Cost of Firing"

I pay 14 cents per KWH therefore cost to fire a bisque over 13.5 hours would be approx $13.60

[Markalanb]

That is just what I needed to know.  I am glad I found this site.  You all have given me invaluable information today.  My current KW cost is $.17 per KW.  So from your formula , the cost per firing would be $16.49.  with that KILN.  I can do that.  Especially in the winter when my electric use is cut by 2/3's.  

[Markalanb]

The best thing is I already have a 240 V sub panel the previous home owners had installed for a large hot tub which is now gone.  

[liambesaw]

And that's a 7 cuft kiln, it's pretty good sized. I have closer to a 4 cuft kiln and i fire two times every weekend and haven't noticed a difference in my electricity bill.

[Markalanb]

Ok, I have a very important question.  There are 2 used Kilns available on Craigslist.  one is a Cress Skinner kiln LT-3K for $300,  the other is a Skutt KM1027-3 kiln for $400.  Any opinion on which would be a better choice.  I know there are probably a dozen opinions but thought I would ask.

[liambesaw]

Depends on their condition but I'd go with the skutt if they're the similar.  The lt3k is the model of kilnsitter, not the kiln

[neilestrick]

The Skutt will probably be simpler to operate and repair.

[karenkstudio]

I built a portable wood fired Raku kiln using a trash can, and also experimented with a bisque firing using the same kiln.

It was successful only because I slowly brought the kiln up to an appropriate temperature for clay formulated to be used for raku.

A picture of the kiln with the bisque pieces is attached.

To bisque fire in this type of kiln would take some experimentation.   

 

[neilestrick]

It is difficult to bisque in a raku kiln. They are made to fire fast, so slowing them down can be tough. If you had a different burner that was lower power for bisque, it could work well.

[liambesaw]

I did it for a long time, but I added a chimney and damper so it was pretty easy to slowly heat it up.  It's a lot harder to slow down the cooling

[Liam V]

I found a steel drum someone threw out and fired two greenware pots in it with a wood fire. The fire lasted about 2 hours and I let it cool for another 5.

One pot broke and the other one works fine as a planter; I'm currently looking for an electric kiln so that I can make foodsafe pottery.

I imagine a pit fire would function similarly.

edit: I used stoneware clay for this

[Markalanb]

Ok. Well I made a committment and got a electric kiln.  I think I did well. It's an older model Skutt KM-1027 for $100 plus the cost of one element.

SO I did start throwing and had a new question.  How and when to attach a handle to a thrown piece.

[Benzine]

42 minutes ago, Markalanb said:

SO I did start throwing and had a new question.  How and when to attach a handle to a thrown piece.

When the body has set up enough, that it won't deform from the pressure of attaching the handle.  Usually on the softer side of leatherhard.

After attaching, it is a good idea to cover the ware, so it slows drying allowing the two pieces to better join.

[Markalanb]

Thank you.  This is the best sight I have ever found for getting responses to questions.