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glinum

Gas kiln won't heat up above 650C/1200F

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That is really sad to hear!

What was the temperature outside? I think I wrote before that my firing was depending on that very much. I could never imagined that for example 20 C difference (in outside temp) makes such a huge difference in firing. For example at summer evening (cca 17C I think) I could not get it over 1000-1100C

The problem is that every little thing makes a big difference. I noticed that when something blocked the progress it was time to make changes. I am trying to say that when you saw that you are not getting above 600 C it would be better to stop and not waste any more gas.

 

as marcia wrote:

see if you get a pull of a draft with a lit newspaper torch by your burner port. This is important since you are using a natural draft and no forced air.<br style="color: rgb(28, 40, 55); font-family: arial, verdana, tahoma, sans-serif; font-size: 12.727272033691406px; line-height: 19.09090805053711px; background-color: rgb(250, 251, 252);">

 

have you tried that?

My kiln is much simpler (and it fired to 1250 C at least 30 times, but it was summer), the air just has to go up and not around... the newspaper torch could tell you if you have enough air.

The chimney is not a good idea in my opinion. Before you quit.. maybe try a hole on the upper side of the barrel (in the metal). The thing is small and the temperature will be high enough everywhere.

OH another thing- you might not have enough insulation or the shelf is positioned to low (it could suppress the fire). I am having more room under.

Maybe it is just a combination of all those reasons.

I would try different solutions:

- first the newspaper torch (if that is ok then ...)

- firing in a warmer room or a warm day (this will tell you about the insulation)

- then the upper hole

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Hallelujah! smile.gifbiggrin.gif

I finally sorted it out. The reason was quite simple - I had to throw away the pressure reducer. For some reason I thought it's not ok to run a burner without it, but I talked to another Ukrainian potter who uses similar setup and he said he runs it without the reducer.

reduktorlag.jpg

 

 

So no other tweaks were actually necessary if I got rid of it on my very first firing. The burner size was ok, the holes were ok, the flu, the draft etc. were ok.

I climbed to 1040C/1900F in about 8 hours and the burner was only 70-80% open, so I believe I could easily climb to 1250C/2280F if I wanted. But I was firing earthenware so 1040C/1900F was just fine.

When I opened the burner some more the reduction flame ran out the top hole. That is so exciting! smile.gif I didn't actually need it for bisque firing, but now I know I can do reduction firing if I want.

 

Check out the

.

 

Here is the picture of the fired pieces I made this morning.

piecese.jpg

 

I have some questions about color changes but will post it later in a separate topic.

 

This is what happened to the shelf:

shelfq.jpg

Probably it will live a few more firings and then I'll buy some good kiln shelf, because this one is not.

 

So this topic is now in resolved status biggrin.gif

Thanks to everyone who tried to help, I really appreciate this.

 

Andrey

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Yes, I am going to build one. Is it OK if I use the "weed burner" (I think it's used also for fixing/building special type of roofs) burner they sell in hardware stores?

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I finally found a business, that sells ceramic fiber blankets.

They have few different options available:

50 mm thick (~ 2") for 1260 C (2300 F)

and

50 mm (~ 2") thick for 1430C (2606 F)

 

They also have it 25 mm thickness and for the same temperatures.

 

What do you recommend? 25 or 50mm?

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Although this instance is resolved, I thought I would throw in a picture of my raku kiln. Sorry I don't seem to have a better view to show you. This was loosely based on a design by Daryl Baird shown in a Pottery Making Illustrated article titled Raku Lite from the July/August 2007 issue.

 

It uses 1-inch (2.54 cm) inwulation and one weed burner from Harbor Freight. The base is insulating fire brick on expanded metal, framed with angle iron, and some inexpensive plastic casters under. The outside of the chamber is expanded metal lathe such as used for plastering, or backing tile base. It gets to temperature quickly, but one must start with the burner in, or close to, the burner port and gradually move it back as temperature and gas flow increase. It will get to temperature faster than I fire it, but 45 minutes of slow climb is what I prefer. I block the exhaust port partially with a piece of kiln shelf early on to retain heat as an adjustable damper. I use a 20 pound tank and no regulator.

 

I fire Western raku, naked raku, ferric fuming in foil, and carbon fuming with great results from all.

 

Johnpost-2045-137088639317_thumb.jpg

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