Bisque Firing Tips For A Small Ultra Fast Firing Gas Kiln

[AVPottery]

I now have an 18" gas converted kiln which fires super fast.  This seems like an issue for bisque firing as you need to go much slower.  Has anyone else had experience with something like this. It seems like their are two temps that are really important to take slowly.  300 for a few hours, water separation around 800, quartz inversion around 1100, then finish to cone 06-07.  Any tips for a firing schedule?  

 

The issue with gas is that it heats up fast then plateaus because the gas supply at any given level from the valve.  Its really hard to increment 10 degrees.  It seems like any gas valve changes will give me 50-100 degrees F, in temp change.  For reference I am using a Summit GV-18 conversion burner, 100k BTU output.

 

Thanks for any feedback,

 

-Andrew     

[Marcia Selsor]

Is there a regulator of the gas line? You can turn the pressure down and control the output of the burner better. For that size you  should start off with a "candling" very slow...licking yellow flame very small.

 

 

You need to hold more at 200 than 300 for steam. 

[AVPottery]

Is there a regulator of the gas line? You can turn the pressure down and control the output of the burner better. For that size you  should start off with a "candling" very slow...licking yellow flame very small.

 

 

You need to hold more at 200 than 300 for steam. 

200 I can hold but i get a lot of really black soot when i do that.  I suppose thats not an issue since it will all get burned out.  

[Mark C.]

Is this propane gas kiln? If yes than get a regulator and use that to turn down/up pressure

The key areas to move slow  thru are 200 ,800 and quartz inversion

after quartz you can fly.

This kiln is so small it will always be hard to slow down and also slow cool.

[Callie Beller Diesel]

The black soot at that early point is what's causing your black coring. Look to your air supply if you're getting that kind of dirty burn on low. It may be that more than your speed.

 

Edit: I re-read your rutile post. You don't have black coring, but if you have black smoke at 200, you'll get it.

[Marcia Selsor]

If you are getting black, you have a rich gas flame. cut back on the gas and add air. you don't want a hard flame to begin with on greenware. Do you have a regulator on the line.? I think they are critical in controlling the gas flow.

 

Marcia

[AVPottery]

The black soot at that early point is what's causing your black coring. Look to your air supply if you're getting that kind of dirty burn on low. It may be that more than your speed.

 

Edit: I re-read your rutile post. You don't have black coring, but if you have black smoke at 200, you'll get it.

 

Its not black smoke so much as it is soot from the pilot flames.  I suppose because they are just not hot enough flames.  I can use them to candle the kiln arround 200-250 I suppose.  The large burners put me over 300 though.

[AVPottery]

If you are getting black, you have a rich gas flame. cut back on the gas and add air. you don't want a hard flame to begin with on greenware. Do you have a regulator on the line.? I think they are critical in controlling the gas flow.

 

Marcia

 

I do have a regulator, I can give it a shot to see I can restrict the burners enough to burn low.

[curt]

Slow climb to 200 for water smoking (don't really need to hold there I think) and if your ware is thin could be less than this before you start to climb more rapidly (say 175 or even 150).

 

I think chemical water releases around 600 to 650 rather than 800.

 

I always soak at 800 for an hour before climbing to ensure that organic burnout is complete, particularly if you are using recycled clay or have had problems with bloating before.

 

Might think of holding the top temp for 15 or 20 mins to even out the temperature all around the Kiln if unevenness is an issue.