Kiln Help

DawnT · #1 2009-06-06, 4:28pm

Hi everyone,

I've been working mainly in boro glass but recently started playing with soft again. The last two batches of beads that came out of the kiln have marks from where they piled on each other. My controller seems to be running the program fine and says the temps are normal but they just can't be. So my question is what is the most likely cause and where can I find replacement parts? I have a Chili Pepper kiln. Thanks so much!

tajones1463 · #2 2009-06-06, 5:04pm

Dawn,

What elevation are you at? I had the same problem and everyone (including the kiln company) told me the elevation WOULDN'T effect the kiln temp. However, the kiln checked out as good and the controller was working properly. I didn't know what else it could be. So, I decided to run an experiment. I backed down my annealing temp 5 degrees each firing until I landed at a temp that did not cause my beads to melt. That temp for me is 940 for 104 glass. Now I anneal at 940 all the time with no problem.

our elevation here is 6,000 ft above sea level.

Good luck!

DawnT · #3 2009-06-06, 6:01pm

Theresa, we're at around 5000 BUT I've had my kiln for almost 5 years and it's never done this before so that's why I'm pretty sure something is going bad. I've replaced the relay once and I don't think that's the problem here but who knows. I did lower the temp by 10 degrees the second day so I guess I'll try going down a bit more for now.

Crazy Woman · #4 2009-06-06, 8:07pm

Hi, Dawn ~ Are you making sure to put the new beads in and let them sit without touching for a bit before touching anything else. Just a thought.

DawnT · #5 2009-06-06, 8:52pm

Hi Leslie - yep I put them all in a row until it's full across and then take the oldest half and pile them. I even made sure the glow was gone from all of them before putting them in. It has to be the kiln getting too hot - I've tried everything I can think of!

ArtcoInc · #6 2009-06-07, 12:49am

Thermocouples do drift with age ...

If you have access to another pyrometer, compare the temperature that the controller reads to the standalone pyrometer.

If you don't have another pyrometer, you can crudely calibrate your kiln yourself:

Pull a thin stringer of your standard glass. In a cold kiln, put two pieces of kiln furniture in your kiln several inches apart. Place the stringer on top of the two pieces of kiln furniture. Heat your kiln up to, oh, 800°F. Wait 5 minutes. Open the kiln and look at the stringer. Has it sagged any? If not, raise the temperature 25°. Wait 5 minutes. Has it sagged yet?

Continue this until the stringer begins to sag. Note the temperature. Program your annealing cycle to be 25-50 degrees below this temperature.

Note: You may have to fine tune this some, but it will give you a starting point.

The other option is to just buy a new thermocouple. But, I'd still run this test first ... just to see.

HTH

Malcolm

Carolyn M · #7 2009-06-07, 8:18am

Dawn, what glass are you using. There are some soft glass colours that should never touch, they always get kiln kiss marks if they do.

DawnT · #8 2009-06-07, 7:27pm

Hi Carolyn - it's clear! Lauscha and Vetrofond and I've used them for years and not had a problem.

Malcolm - I don't have any "kiln furniture" is there something laying around my house that might work for the test?

ArtcoInc · #9 2009-06-07, 11:55pm

Quote:

Originally Posted by DawnT

Malcolm - I don't have any "kiln furniture" is there something laying around my house that might work for the test?

Pieces of an old flowerpot? Two stainless steel rod rests? A couple of rocks?

Something that is made of brick, porcelain, stainless steel .... anything that will withstand the temperature.

Malcolm