Can I Get Away Without A Test Kiln?

[Saki]

I am a hobby potter who is just starting to experiment with mixing glazes. So far, I have included my test tiles in my regular firings (∆6. However, because I am not a production potter, I don't have enough work to fire a full kiln as often as I would like test glazes.

 

So I am debating whether to buy a test kiln or to fire test tiles in my large kiln (skutt 1027) without a full load of work. I realize that firing the large kiln is more expensive per firing, but I don't really see myself testing glazes frequently enough to justify purchasing another kiln. 

 

If I fire the test tiles in the large kiln, would it be terrible for the elements, thermocouple, or other parts of the kiln to fire without a full load? Will I damage the kiln or shorten its useful life?

[MatthewV]

I know of no harm in firing an empty kiln. I might add a few shelves; I have found single probe kilns fire better when there is a shelf above the thermocouple. You could also start making large bowls! They take up huge amounts of space and sell pretty easily too.

 

The math: including wear of elements and electricity, your kiln costs about $20-30 to fire. A test kiln should be ~$5? So... maybe a $25 difference.

 

Conclusion: I would just continue using one kiln until a good cheap test kiln came up on craigslist.

[Marcia Selsor]

I agree with Matthew. Maybe the idea of filling a kiln with shelves rather than pots will inspire you to make more pieces. You could practice throwing tooth pick holders or other small objects and use them as test pieces too. You can fire a very spacious kiln with test tiles but as Matthew says you need to occupy the space with something to get good results in firing.

Marcia

[Saki]

Thank you both! I can definitely add kiln posts and shelves, and the suggestion to use large bowls is a great excuse to work on pieces pieces I don't normally do.

 

Matt: My kiln calculates the cost at ~$6/firing, based on electricity usage and the billing rate that I got from my electricity bill. The difference between $6 and your estimate of $20-30 is quite significant. Is that additional cost due solely to the wear on the kiln elements? Or do you think the kiln estimate is just unreliable?

[Foxden]

I have never had a test kiln and know the frustration of not being able to fire test glazes all that frequently (at least based on my own frequency of glaze firings). I took a community class just to experiment with glazes. The kilns at the center were fired a few times each week so I got plenty of tests in over the course of the term. Also, the frequent firings allowed me to make slight alterations of certain glazes and see the results rather quickly.

 

i do prefer to fire test glazes in the same type or size kiln I will ultimately use as the effects of cooling will be more consistent between my actual firing and the firing of the test tile. Of course a computerized kiln controller may make them quite similar.

[Denice]

I have had a test kiln for fifteen years and they are quite handy to have around.  I go through spells where I do a lot of testing but I also use it to fire small projects that can't wait for my big kiln to get full.  The cost of firing a kiln can depend on how much your electricity cost,  I have a big Skutt like you and it costs me about $25 a firing.  I have never figured my test kiln but it doesn't even raise my electricity bill.  Denice

[Saki]

Denise: are you getting the $25 cost from the COST function on the kiln? Just trying to figure out why my kiln is estimating costs so much lower. I fire to ^6.

[Roberta12]

Saki, like you I have calculated what it costs for electricity.....a low fire load is about $5, a bisque load is about $6 and a glaze load about $7.  But when I add in the cost of elements/thermocouples and I know how many loads a month I fire, I just did the math, it is somewhere around $10 a load.  However, the cost of electricity is going to vary depending on where you live.  And you would also need to know how often you fire, (how often you would need to change elements/thermocouples)  I change mine once a year.   You might not need to do that.  So there would be some variables.  And probably some I haven 't thought of!!!! 

 

Roberta

[Foxden]

Here is a good explanation for calculating your firing cost.

 

http://www.lakesidepottery.com/HTML%20Text/Tips/estimating-electric-kiln-firing-costs.htm

[Saki]

Roberta,

 

Thanks for this information. This is my first year with this kiln, so I am not sure how often I will need to change elements and thermocouples. It was my sense that they should last for about 100 firings. Does that sound about consistent with your experience?

 

Saki

[Marcia Selsor]

It really depends on KWH prices where you fire. california electricity is extremely expensive. In Montana it was 0.14/KWH at my coop studio. Cheaper overnight.

In Brownsville, the city owns the utility company an the price .1128/kwh . Prices vary across the country.

I have had my test kiln for about 20 or so years. It has a 9x 11 interior and I can fire mugs and espresso cups in it as well as test tiles. I have never changed the element but the switch went out a few years ago.

 

Marcia

[Saki]

It really depends on KWH prices where you fire. california electricity is extremely expensive. In Montana it was 0.14/KWH at my coop studio. Cheaper overnight.

In Brownsville, the city owns the utility company an the price .1128/kwh . Prices vary across the country.

I have had my test kiln for about 20 or so years. It has a 9x 11 interior and I can fire mugs and espresso cups in it as well as test tiles. I have never changed the element but the switch went out a few years ago.

 

Marcia

The variation in energy costs would only account for a difference of about $1 to $2. For example, plugging in the two rates you gave ($0.14/kwh and $0.1128/kwh), my firing costs would be between $5.55 and $6.89, a difference of only $1.34. So I believe there must be a different explanation for why Matthew and Denise's estimates are so much higher.

[Marcia Selsor]

Both Brownsville and Billings were cheaper examples. California was outrageous.http://www.electricitylocal.com/states/california/

Marcia

[Saki]

Both Brownsville and Billings were cheaper examples. California was outrageous.http://www.electricitylocal.com/states/california/

Marcia

I think it still wouldn't account for the difference. Even assuming $0.20/kwh (higher than any actual rate in the country outside Hawaii), the cost would be less than $10/firing. I don't mean to suggest that's not expensive (because it is!), but it is a lot less than $20-30/firing.

[glazenerd]

That is the benefit of an Orton controller. You can program in the cost of electricity in Kwh and it will give you the firing costs to the penny. Also the benefit of living in a semi-rural area: electric co-op: I pay 0.08¢ per kwh. My 6.5CF top loader cost me 8.35 to fire to cone 6, and my 16CF front loader cost me 12.47 up to 14.30 pending holds. My 0.25CF test kiln runs a $1.

Saki, given your most recent post in glaze chemistry I would recommend a test kiln. Glaze testing junkies like myself, and you are headed in that direction: need one. My little 0.25CF test kiln holds 2-6" round test tiles right nicely. Also have a 1.75CF Paragon 1613-3 that I think would do well for you: cost about $2.50 to fire. It has 6400watts of power which means you can fire a regular glaze fire, or BLOW through a test firing. It has an Orton 4.0 controller: basic programmable model: but more than enough flexibility to do the job. With a type S thermocouple (which you do not need unless you are firing cone 10 all the time), it ran $1500.00. Get a type K, it will run around $1200.00 .For that money you get a programmable controller, and 6400 watts: which is nearly double the power of most kilns that size.

Option 3: watch craigs list or other sites for a good used (cheap) small kiln for testing. Small kiln = 0.50 up to 2.0 CF

Nerd

 

 

small one is 0.25CF, and the larger one is 1.75CF, Yes, I took the controllers off to keep heat away from them. Strongly do not advise others to do that: my studio is locked, no kids around, and other people are not near them. The breakers are off at the box, and turned on after I load for safety.

[Mark C.]

(california electricity is extremely expensive)

 

Bingo

[Denice]

Saki I include the cost of replacing such items as elements, shelving, kiln setter parts, cones.  It's like owning a car, when you figure out how much it costs you to own a car per mile you have figure in oil changes, tires, insurance, wear and tear, property tax, gas ect.  For example this year I had to get a new lid, a full shelf  and replace the thermocouples on my Skutt digital  dual thermocouple.  I can tell that I am about ready for a rewire but I have already rebuilt this kiln twice so I am going to bite the bullet and get a new one.    Denice

[neilestrick]

Denise: are you getting the $25 cost from the COST function on the kiln? Just trying to figure out why my kiln is estimating costs so much lower. I fire to ^6.

 

When you calculate the cost of your electricity, make sure you're looking at your bill correctly. On my electric bill there are two different main charges, and several other small charges which go into the total- Supply Charge, Delivery Service, Taxes, etc. So if I just look at the cost per KWh, it won't be accurate. You have to take the total cost on the bill and divide it by the KWh used that month to give you the true cost of firing. That said, the cost of electricity can vary greatly around the country. Last time I checked, for it was just under 17 cents per KWh. I estimate my big 21 cubic foot electric to cost me around $35 per load, and I can get electric bills of close to $500 a month for my shop in the winter when the baseboard heaters are running, too. Thank God for budget billing! A 10 cubic foot kiln like a Skutt 1227 I would expect to be in the $12-20 range depending on where you live. A little 1 cubic foot test kiln should only cost a couple of dollars, so within 100 firings you could make up the cost over firing the big kiln empty.

 

Whether you end up getting a little test kiln or fire the big one empty, you'll need to put in a cooling cycle. An empty big kiln or a little test kiln will cool much slower than a full big kiln, and that will dramatically affect your glazes. It doesn't necessarily have to be a 'slow' cooling, but something that will be consistent in all firings. You should set it to cool from the peak temperature, since crash cooling from the top will also be different in each situation. I cool at a rate of 175/hr down to 1500F, which takes about 3 hours. My big kiln hardly clicks on at all during that cycle once it gets down a couple hundred degrees, and I get identical results from all 3 of my kilns. My test kiln cools so quickly that many glazes come out really bad if I don't slow down the cooling.

[neilestrick]

I've gotten a couple of little manual test kilns for $100 each that run on a 110V 20 amp circuit. With kiln that size you can add an external digital controller for around $500.

[glazenerd]

 

neilestrick

  Whether you end up getting a little test kiln or fire the big one empty, you'll need to put in a cooling cycle. An empty big kiln or a little test kiln will cool much slower than a full big kiln, and that will dramatically affect your glazes. It doesn't necessarily have to be a 'slow' cooling, but something that will be consistent in all firings.

Excellent advice sir!.   Not required for crystalline because of ramp holds, but I do program a cool segment on regular ^6 when testing.

[Saki]

Denise, Neil and Nerd,

 

Thank you all for your helpful advice—especially the part about controlled cooling. On review, it really does seem like a test kiln is the way to go. I like the idea of getting a used manual kiln and adding a digital controller, but I'm a bit concerned I may not know how to shop for and evaluate used kilns. Neil, if you decide you want to sell one of yours, let me know!

 

Thanks,
Saki

[glazenerd]

Saki:

 

Just post your question about used kilns, along with relevant information, and our staff of kiln experts will assist you with pricing. Again, thank you for choosing Ceramic Arts Community for all your kiln and clay needs. Remember that Friday is Ten for One day: ask one question and receive ten different answers-Free. You can also choose our "Early Email Reply Option", and receive answers about questions you never asked

 

Nerd

 

Y'all come back now-hear!

[Saki]

^ Too funny!

 

I hope I haven't been asking too many questions— I have been overwhelmed by generosity with which everyone has shared their knowledge and experience!

[Joseph Fireborn]

Put it this way. If your interested in developing you own glazes or tweaking others. A test kiln is an invaluable tool. If I had a small test kiln I would be running test almost every single night. I fire test in my 2.7CuFt kiln, and even though it is small it still cost around $200+ to replace elements. I replaced them about half a year ago and I have already fired 50 or so glaze firings which the majority were to test glazes. So it can get expensive quick. My electricity in GA is very cheap though, and we get deals for using more electricity at night or something, which is when I fire my kiln. 

 

If I had the money I would buy a test kiln. If you don't, use what you have and figure out a way to make it work. Make more pots like Matthew said. Large bowls sell easy. If you want to sell them even faster, attach a little bird on the rim... 

[High Bridge Pottery]

I bought my test kiln for £67 about $90~ although it only has on or off until I work out the controller. There are some cheaper broken kilns if you want to have a time fixing them. Just keep looking out on usual sites.