natural gas kilns

[alaskasusan]

Hello to all. I live in Alaska and so am somewhat out of the mainstream.
I have been searching and researching gas kilns. Electricity is very expensive here and natural gas is cheap. I am planning to build two kilns. I have had conflicitng expert opinions on the feasablity of gas kilns for fusing, slumping casting, annealing. I know there is a line of gas kilns from the Netherlands, but these are primarily used for glass painting. I know the Romans did glass casting obviously without electricity.
I need solid information. Does anyone out there have any or can you direct me to someone who might?
We can build practically anything.

[Michael]

Hi, I know of two people who use hoff? gas kilns to fuse and slump in,(art glass and float) they say there're great ....much cheaper than electricity.

[watershed]

Two directions, no answers.

One look up Dudley Gibberson (he's online), a very good kiln/oven/furnace building book.

Second look for Hot glass people who have "Garages". These are small ovens , gas fired, for keeping bits of stuff hot, while the rest of the piece is blown. They have to have pretty strict temp control, otherwise you will slump the stuff you just made.

Oh third, ask over at craftweb.com, there are some pretty clever builders there too.

Oh and fourth, as an interior guideline (flame protection) I'd look towards the pottery kilns, bag walls etc.

So maybe more than 2 directions, but still no answers. Keep us informed please.

Greg

[Kevin Midgley]

I would be careful building my own gas kiln. You need backup systems in place in the event of power failures etc. I was once told that one of the products of combustion of natural gas was water vapour which if the conditions inside a kiln are right, can explode the kiln.
Although electricity is "expensive", you use practially all the energy that goes into a kiln. With gas, huge amounts of energy go up the chimney and are wasted. My fibre kilns only cost about 50 cents @6cents a kwh to do a slump firing. Gas also has building inspectors and insurance agents getting excited. It is your choice but it has also been suggested in other posts that color striking might happen more easily in the presence of gas. Kevin

[alaskasusan]

Thanks to all for your comments. I have spoken to Dudley G. His opinion is that gas kilns cannot be precisely controlled to the extent needed for fusing, slumping and casting. I have heard differently from other sources. I am waiting to hear from anyone who has actually used a natural gas kiln. I keep hearing about people who do, but nothing directly.
The comment about condensation is interesting, I have never heard that before.
As for expense, my tabletop bead annealer can cost me $100.00 a month alone.
Please keep the information coming.

[alaskasusan]

Has anyone used a Hoaf kiln?

[Kevin Midgley]

Not used one but their literature 15-20 years ago as I recall was claiming something like 8-15 minutes for a firing. If you want production, the way to go, but very pricy. Your insurance agents would not get as excited about a commercially made gas kiln as they would about a home made one!

[Don Burt]

Has anyone used a Hoaf kiln?

The Hoafs that I've seen used (Dick Millard's, Paul San Casciani's) were more suited for glass painting and other surface decoration than fusing. I'm not certain if they are even intended to go as hot as fusing temps. But they can cook glass paint and cool to handling temps while you eat lunch. Gil Reynolds sells them and provided some info last year on this board. They're pricey - I can't understand it either, they're not that complicated looking and I'm sure there are tens of thousands of vitreous painters out there just chomping at the bit to improve their firing turnaround time. Hundreds of thousands maybe. Mark them down Gil, and you'll improve sales by at least one this year.

[alaskasusan]

I spoke to Gil Reynolds and I also emailed Hoaf. The temperature problem can be solved with a very precise controller, which allows you to fuse, slump, etc. Unfortunately it costs $3000.00. Plus , of course,there is the kiln. I can kind of understand why it is so pricey. Compare it to the programmable controllers for electric kilns which are easier to operate. Hopefully, like every other technological marvel it will come down in price, like DVD players and computers. Until then, I am still searching. This does seem to be the best info yet.

[Jack Bowman]

Buy an electric generator driven by a natural gas engine.

Jack

[alaskasusan]

That is a very intriguing idea. I didn't know there was such a thing. A new area of research. Thanks.

[Kitty]

i'm paying 22 cents per kilowatt hour, and the first month i had my big kiln, i fired many, many times, i think nearly daily, and my bill was $150. to achieve this, i never turned on the AC, cut back on use of appliances somewhat, and generally behaved myself with electricity. i had no idea what the bill would be, so i was pleasantly surprised. kevin is right about the building inspectors flocking ... i know that has happened here with friends' natural gas ceramics kilns. how much are you paying per kilowatt hour? i'm running a Paragon GL22AD, 220V, on a 50amp dedicated circuit. i also fire a small Cress kiln everyday, but i know that one only costs about 35 cents per load. it runs on 110V. kitty.

[alaskasusan]

Your costs surprise me.Very reasonable for theamount of work. It makes me wonder why I have such high electric bills when my rate is just under ten cents per kwh. I have a good size tabletop bead annealer that I have been using for small fusing projects and lampworking and sometimes it costs an extra $75 to $100 a month. But if I am careful this might be doable. No AC needed up here, but it gets so gloomy in the winter with only five hours of daylight, we tend to put the the lights on just to keep sane.

[Kitty]

i wonder if it would be possible to test your electric bill for a month without the annealer. do you think there could be another culprit in your house, like a refrigerator that is gobbling energy because it's old, or maybe some kind of a heater? you could test how much that annealer uses by looking at your meter for a defined period of time, and seeing how much juice gets consumed, with as much other stuff off as possible. just a guess that maybe it's not the annealer. kitty, fan on, AC off still.

[rosanna gusler]

it is also possible that you have a bad meter. if your usage is off compared to other samesized houses/apartments. i had that happen once in an old shack i rented. rosanna

[thebes]

I actually found this thread while searching with very little luck for propane kiln info. Unlike alaskasusan, I do not have the option of purchasing electricity at any price, the nearest line is 6 miles away.

I am a former fine arts major and have been researching a few different mediums. Warm glass appeals to me and I think there is a definate market where I live (Taos NM). I am absolutely not into having an in town studio, I live way in the middle of nowhere and like it that way. I use solar and wind for household electic but to upgrade to the point of being able to do, say, a firing a day would cost $20k to $50k, obviously not practicle. I could get a generator, but my cost per kilowatt hour would probably be over 60cents after maintenence is added in, maybe more with the way gasoline is going up in price; and I couldn't justify burning that much gasoline when we're in another oil war as it is.

So, no gas kiln, no warm glass for me. I would hesitate to spend 3 grand on a kiln before I was positive that warm glass was what I wanted to do for the next few years.

I was wondering if there is any good reason I couldn't just use a used propane pottery kiln with a pyrometer and keep a close eye on it. I suppose I would need lots of testing to find cold spots, etc. Insurance and code enforcement are nonissues, I don't have any use for them. Even if this would provide only a fair solution, it would give me the experience I need to know if I want to do warm glass.

Thanks,
Thebes

[Bert Weiss]

I actually found this thread while searching with very little luck for propane kiln info. Unlike alaskasusan, I do not have the option of purchasing electricity at any price, the nearest line is 6 miles away.

I am a former fine arts major and have been researching a few different mediums. Warm glass appeals to me and I think there is a definate market where I live (Taos NM). I am absolutely not into having an in town studio, I live way in the middle of nowhere and like it that way. I use solar and wind for household electic but to upgrade to the point of being able to do, say, a firing a day would cost $20k to $50k, obviously not practicle. I could get a generator, but my cost per kilowatt hour would probably be over 60cents after maintenence is added in, maybe more with the way gasoline is going up in price; and I couldn't justify burning that much gasoline when we're in another oil war as it is.

So, no gas kiln, no warm glass for me. I would hesitate to spend 3 grand on a kiln before I was positive that warm glass was what I wanted to do for the next few years.

I was wondering if there is any good reason I couldn't just use a used propane pottery kiln with a pyrometer and keep a close eye on it. I suppose I would need lots of testing to find cold spots, etc. Insurance and code enforcement are nonissues, I don't have any use for them. Even if this would provide only a fair solution, it would give me the experience I need to know if I want to do warm glass.

Thanks,
Thebes

Thebes

You can get a kiln control system that can control a gas kiln just like an electric kiln. They are not cheap though. The other solutions are to work thin and not need to control annealing much, or you could try a generator and a small electric kiln that makes jewelry. I wouldn't invest in a gas system unless you can mess around with one enough to know that it will work for you.

[Ralph]

I was wondering if there is any good reason I couldn't just use a used propane pottery kiln with a pyrometer and keep a close eye on it. I suppose I would need lots of testing to find cold spots, etc.

Thebes

You can do this. Many small propane-fired soft-brick pottery kilns drop temperature at a sufficiently slow rate to anneal 1/4" glass. Fibre kilns cool faster -- maybe too fast -- but that can be dealt with.

If you have a kiln, fire some initial glass tests to fuse-temperature -- not work you've spent time on -- just pieces of glass of the size/thickness you intend to use. Turn off the gas, close the flue and allow the kiln to cool naturally and check the results for annealing (or other) problems.

If you find it necessary to slow down the temperature drop (for a fibre kiln or for thicker glass) you can "fire down" -- that is, turn down the gas valve slightly until the temperature starts dropping. You should find that each "turn-down" of the valve produces a temperature drop followed by a plateau. A bit of practice should give you good control over the temperature. The caveat is that you will have to pay close attention -- a digital pyrometer makes it easier.

Gas control in small kilns is usually different to electric where the current is either full ON or full OFF and a controller times the switching. With gas, a simple needle valve adjusts the gas flow and the kiln temperature can rise, fall, or hold with very few adjustments. Gas doesn't need to be turned on and off constantly like electricity so human monitoring is not as demanding as you may think.

Summary: for small-to-medium sized 1/4" thick glass pieces fired in soft-brick kiln, natural cooling may work perfectly. But if required you can readily nurse a gas kiln through a glass annealing schedule. An attentive human between a digital pyrometer and a gas needle valve is a fine control system.

The rising-temperature part of a propane glass-firing is a lot like a pottery bisque firing - very slow in the initial stages to avoid heat shock. Potters take the same care with a bisque to "burn-off" chemically combined water in the clay. A good move would be to observe an experienced potter carry out a bisque firing in a gas kiln. Even better would be to do some initial glass tests with a sympathetic potter.

The gas-fired approach becomes less attractive if you fire thick glass or require extended annealing schedules. The inconvenience of staying with a kiln is OK for maybe 7-8 hours but less attractive for longer.

And yes, you will have to take care with temperature distribution in the kiln. Smaller gas-fired kilns (especially those with a single burner) are notoriously uneven. Do the same "sag" tests that BE recommend in "Getting to know your kiln".

Ralph (long-time potter now working in glass)