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Pam S

Firing Questions

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I am a sort of neophite potter. Been working though a local recreation center for about 15 years. We threw, bisque fired, glazed and everything came back to us. Most of the glaze firings were good, sometimes we made mistakes, too thick, too thin. The usual. My friend and I have started a small home studio due to the closing of the Recreation Centers Art Program. We purchased a used L&L Jupiter manual kiln (small). It has three firing zones and a kiln sitter as did the larger kilns we used at the rec center. Our problem is in the glaze firing. We inherited a few glazes from the original studio and have made several from recipes/formulas that we made at the rec center. Some of the chemicals were inherited and some are new. We've fired several test batches with mixed results. The clay bodies are Buncoumb White and Mary's Porcelain, both cone 6. We bisque fired to ^04 as we did in the studio. Glaze fired to ^6 with several schedules and have had some success and some really bad results. I thought we had it down and fired multiple pieces (10 goblets for a wedding) with a disaster! The glazes that I had test fired ran like crazy! I'm bummed, but the bride is even more bummed! I've kept a firing log, so I can provide more detailed info. I'm/we're discouraged that the glazes that we are use to aren't true and the new ones are failing. The tried and true matte white silk is turning out shiny with a bit of crackle and the tried and true eggshell matte is now shiny without the usual speckling. Don' s Floating Blue and Ocean Green ran like crazy in the last firing. Any advise is much apprechiated!Thanks! P

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Need a tad more information for one quick thought I have .

 

Do you know the size and type of kilns that the rec center was using for the firings that had the matt glazes that now are coming out shiny?

 

I'm guessing quickly here that the shiny versus matt thing is due to the cooling cycle of your kiln. Cooling has more to do with glaze development than you thnk. A larger kiln with more thermal mass or a kiln with more insulation will coll slower....... promoting the micro-crystaline growth on the surface that many matt glazes depend upon. It is also possible that they knew this fact and were firing down with a computerized controller on a similar sized kiln.

 

Are you using witness cones on the shelves? Are you using a "cone fire" program?

 

best,

 

..................john

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Help! I am having some issues with a kiln yard set up. I am firing with natural gas that has been set up by the city. The gas line is hooked up to a cone 10 downdraft about 30 cubic with safety features. The same line goes to a fiber drum raku kiln with a seperate safety system and then the same gas line goes to another cone 10 up-draft again with safety features. Each kiln has seperate turn-offs, safety systems and all fire great! But I do not fire all at the same time. Here is whre I need the help. The city inspector is questioning the safety of the "gang" system. My experience shows this to be standard. Any ideas where I can get "professional" explanations of the validity of this system!?

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Help! I am having some issues with a kiln yard set up. I am firing with natural gas that has been set up by the city. The gas line is hooked up to a cone 10 downdraft about 30 cubic with safety features. The same line goes to a fiber drum raku kiln with a seperate safety system and then the same gas line goes to another cone 10 up-draft again with safety features. Each kiln has seperate turn-offs, safety systems and all fire great! But I do not fire all at the same time. Here is whre I need the help. The city inspector is questioning the safety of the "gang" system. My experience shows this to be standard. Any ideas where I can get "professional" explanations of the validity of this system!?

 

 

Hi Sandra.

 

I do professional kiln design and installation and workshops and such.... been doing it since the 70's. Used to do this work for Cutter/ Eagle Ceramics years ago....as well as privately for my own business since then. VERY hard to diagnose this kind of stuff accurately from afar and without DETAILED information (and images and such).

 

That being said........

 

If the inspector is happy with the individual separate components of the flame safety system as to their suitability for the intended purpose, then the sum total of the parts should not be an issue. Are you sure that you fully understand his/her exact concerns? It DOES sound a bit strange to me.

 

Is it maybe that you are exceeding some maximum BTU city code for a single location if they all were on at the same time? (Certain BTU draws on a single units typically can kick in "heavier" regulations for flame safety complexity.)

 

If the capacity of the gas supply (due to line size. meter capacity, limiting plates, etc.) is such that IF your were to try to fire all the units at the same time you would then have a pressure drop on the main line that resulted in a lack of stability of the individual burners,....... then the flame safetys on the individual units would shut off those unstable units.

 

It is VERY common to have multiple units sharing a main gas supply with individual branches off that main.

 

Maybe he/she is concerned because the main gas supply was not sized correctly for the whole "big picture"....... and the kilns were added sort of piecemeal over the years to an existing meter/ gas line that is under capacity?

 

Are each of the units set up individually on secondary 2nd stage regulators? Or is there only one regulator on the entire system at the meter area?

 

I'd be asking for a very detailed explanation of exactly what the concerns are. In some cases it REALLY is simply that the inspector has not a CLUE about ceramic kilns. And they have to put THEIR signature (and reputation / job) on that line in signing off. What you might have to do is perform a bit of gentle education to get them comfortable with the whole deal.

 

Hope this helps.

 

best,

 

.................john

Sandy A likes this

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Hi John,

We have a similar situation at our college studio, which was built about 3-4 years ago.  It's a beautiful studio and is supposed to be 'state of the art'. Inspections passed and all was fine until we got a new fire marshall.  He red tagged it and claims the raku kiln needs to be 50 feet from any building, etc. Where can I find reference information to give him 'gentle education' as you say to get our kiln back on?

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