inaccurate kiln temps

[rustyglass]

I dont understand how a 3 month old kiln could be so far off. I made a bunch of things today, set the kiln to ramp up to 1150 for 30 mins to strike some of the colors.(like I always do) I came back about 3 hours later after it had cycled down and one of the goblets I made slumped over, tipped over onto another piece which was laying down and they both broke. :mad1: Another one has the gangster lean going. I dont get it. what good is a kiln worth $2000 if after three months it already isnt accurate??? I have held back badmouthing this kiln company on this board but this is one of MANY complaints I have about my newest investment. So after investing in an expensive kiln with a digital controller, I have to invest in a pyrometer now to check it????? F- that. Im pissed. Is that why its name starts with F-?



Edited for profanity. ;)

[WORLD FAMOUS]

Hey Rusty,
Sorry to hear about your loss, that really sucks to come back to when you're all excited to see what you made. You have to remember the weight factor of the goblets...heh. The top is really heavy, and if the stem in the middle is thin and gets too hot, the weight of the cup will make it lean over.

Micah will chime in later with some leaner stories he says...lol.

I wouldn't bring it up to 1150 with goblets, or stack 'em upside down maybe so there's less weight on the stem? Try just 1125 or just 1100. Remember the back corners or various other spots could be 'hot spots' too, for instance closer to the door seems to be slightly cooler overall because of the heat escaping the edge so I've had less problems with stuff getting too hot there...

Good luck with the next batch Rusty!

[IrieGuy05]

Paragon F-220?

[T Lewis Glass]

Plain and simple , 1150 is going to slump your glasses . I know you were trying to strike the color out but . Anything over 1050 and your cups are going to start moving on you . Maybe not a lot but they will start moving . I thought at one time , If I set em up at 1075 for a shorter amount of time I could bring em down sooner , and wondered why the hell everything was off center . Sorry to be the bringer of bad news but ,,, dude your going to need to find different colors(non striking) to use if you wanna do goblets . Or self strike after you attach the stem to the foot . At 1050 your struck colors aren't going to clear out on you ........

Food for thought . To me it doesn't sound like there is anything wrong with your kiln .

Anyhow if you wanna get rid of it I'll give you 50 bux :tongue:


~Todd

[jiminyrootkit]

i would also vote that 1150 is too hot.
particularly with anything where weight is supported by a thin piece.
shit, if it floats above the kiln floor, a 3/4 inch marble on a 5mm punty will eventually bow the 5mm at 1055 (when left for several hours)
$.02
-f

[bc]

Sometinmes when the digi controllers go for 1150 they hit like 1250 for a while (no brakes) an that is probably what happened.

[medicatedMELTDOWN]

on my AIM 9169GS the temp changes around 10 below and 10 above what i set it at. how much do other peoples vary?

in Bandhus book i remember reading it shouldnt fluxuate more than 5-10 degrees during the slowcool

[Greymatter Glass]

Another thing to consider also.... Kiln elemnts and Thermocouples both "drift" and no, 3 months is not too short a period to get some drift.

Best thing to do is make sure, first off, that your pyrometer/thermocouple are reading accurately. a 5% drift wont show up at room temp, but at 1000 degres will be 50 degres off, which is enough to ruin things.

There are several ways to calibrate your kiln, I wont go into them here in detail, but if you want I can poost the info later on in another thread.

If the elements have drifted, then the thermocouple should adjust for it, but there's a possibility they're running hot and the pyrometer is out-of-whack. Eventually, the elements will drift so far that no amount of power will keep them hot.... which doesn't sound like the problem you've got.

In the end, you can strike a goblet at 1150 for maybe 2-5 minutes... even that would be pushing it, I'd try 1050 and flame striking before you put the goblets in.

As for the kiln manufacturer, have you called them to see if they can advise you? Don't call and bitch at them, I seriously doubt it's something wrong with their kiln.

It's a poor craftsman blames his tool.

-Doug

[3 rip min]

t lewis and jim are right on.... 1050 will slump 5mm rod with a marble on it no problem..

your kiln is fine...

[ArtGlassHouse]

Sorry to hear about the kiln mis-hap..... I think all of us have stories about broken glass. It REALLY sucks!!! I'd stay at 1050 and flame strike also. OR- When I work a piece with lots of color that make it more fragile and shockable, I create it in three sections. Vase top, Stem, and Foot. Each one is put in the kiln as it's finished at striking temp. The next day, I weld it all together cold.... and anneal it from room temp to 1050 slowly (400 - 600 degrees an hour). No problems on warmping pieces.... and I can anneal 4 or 5, 20" vases at a time that way. (thanks to the HT... I mean Magma Tower... LOL). The other thing is..... Every Kiln is NOT the SAME. 1150 may be fine in a F120, but warp the same piece in a F240! The larger the kiln, the lower the temp is.
An example, full fuse in a quick fire six is 1750, 1550 in a hot box, 1475 in a F120 and only 1406 in a JenKen 24.

[rustyglass]

thanks for all of the replies. I have been using this cycle to strike colors since I have been blowing glass, and this is the first time it has happened. Being the "poor craftsman" that I am, I blamed the kiln. This was not my first goblet I ran on that cycle, but it was the first one to slump and fall over. I always thought it took 1228 degrees to move glass. so I thought I had a cusion of 78 degrees. When this happened I deduced the kiln temp as being inaccurate. I guess you learn something every day.

" I seriously doubt it's something wrong with their kiln. "

Well in 3 months, 5 of the their l.e.d. lights on the digi are out! 5 of them. I can barely read what it says. It has cracks in the their firebricks that were all not there when I got it. It sits on a very flat surface, has not been bumped, kicked, or spit on. And the cracks seem to be getting larger. One of their elements is drooping too......Do you see a theme? This kiln is 3 months old, I didnt think I was jumping to conclusions. I have a smaller kiln that I used for over a year with no problems at all.

No I havent called them yet, I contacted my distributor and they told me to handle it through them, and I am in the process of getting pictures of the problems to send to them.
Thanks.

edit: Hey Ron, we posted at the same time. thanks for that explanation on different temps, like I said, you can learn something every day.

[ArtGlassHouse]

That's the best thing about glass........ everyone is always learning new things everyday (even the masters). Cracks and drooping elements. Hmmmmm. It is normal for their to be "some" cracks in a square style kiln. But, I've never seen them get bigger. I am very familiar with; JenKen, EvenHeat, Paragon and Skutt. The other ones are more for the west coast. Skutt, has free shipping to distributors for large orders is why they are in the East. So, I really can't speak first hand about the other ones. Glad to hear the distributor is taking care of it. It is not normal for elements to hang down in a new kiln...... Maybe after 5 years of being used a few times per week. There are element clips that are cheep and should hold them in place. They look like 1 1/2 staples made from heat resistant metal. You just push them in at an angle so they don't slip out.
The controler sounds more odd to me. I heard of a kiln company with controler problems and they went under. I forget the name, but I can dig it up if need be. Most of the kiln companies are using bartlet or Orton computer boards in them. It is always sad to hear about a "bad apple" out there. It may not be the kiln company, just a one time fluke with a bad kiln...... jolted to death in shipping or something. Let me know if you need any help with anything.
Ron Jr.

[Robert Mickelsen]

No kiln is consistent in its heat and no digital controller or pyrometer is totally accurate. You can calibrate your kiln using either cones or trial and error, but you will have to calibrate it either way. My new kiln (30"x16"x16" interior) has to be set at 1000F. 1050 is too hot. This means that there are hot spots that cannot be adequately covered by the single thermocouple in the back. Since changing all my cycles to 1000, I have had no further slumping problems and no annealing problems to speak of. Works for me.

[Micah Evans]

Hey Rusty, I ran into the same problems when we got our 24 inch aim. I was so excited to make tall work i filled it up in the morning and by the time we got around to running the cycle half of the goblets had slumped over dramatically at 1050, I would say over about a 2 hour period. Robbin gave me a hint on annealing pieces sperately like Ron Jr. also said. After I adopted that way of thinking i haven't had a problem, I also try to time finishing the piece with finishing my day so any unnecissary soak is eliminated. I'm sorry to hear about your other problems i just bought a kiln from the same company, I hope i don't run into the same problems.

good luck and i'll see you in Gainsville tomorrow!

me