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AmyJM

Manual Fire Gas Kiln

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Hi all!  I just finished converting an old electric kiln to gas.  The firing will be totally manual, no kiln sitter involved.  Having never fired a gas kiln, I know my learning curve will be steep!  But I need a few pointers to get started.  I want to start out with a glaze firing, ^5, mainly because I don’t have any greenware to bisque right now.  I have a few “sacrificial pieces” that I am willing to use to start the learning process.  I have a pyrometer and witness cones ready to go.

So, my main question has to do with ramping at this point.  How fast do I want the kiln to increase in temperature on the way up to ^5?  The pieces I have are made from Laguna 52 Buff, and glazed with Spectrum underglaze and/or Spectrum ^5 glaze.  Idk if that makes a difference, or not.  I am a wheel thrower, and I typically throw thin.  Don’t know if that matters, or not, either!

I realize that glaze firing in particular can vary based on the desired effect, but I’m looking for a basic framework to start from.  Based on my small test fire (only brought the kiln up to about 900-1000*, empty, to decide if I need one burner or two) my biggest fear is that the temperature will rise too quickly, and the heat stress will cause issues-up to and including cracking/exploding.

Thanks!

Amy

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38 minutes ago, AmyJM said:

Hi all!  I just finished converting an old electric kiln to gas.  The firing will be totally manual, no kiln sitter involved.  Having never fired a gas kiln, I know my learning curve will be steep!  But I need a few pointers to get started.  I want to start out with a glaze firing, ^5, mainly because I don’t have any greenware to bisque right now.  I have a few “sacrificial pieces” that I am willing to use to start the learning process.  I have a pyrometer and witness cones ready to go.

So, my main question has to do with ramping at this point.  How fast do I want the kiln to increase in temperature on the way up to ^5?  The pieces I have are made from Laguna 52 Buff, and glazed with Spectrum underglaze and/or Spectrum ^5 glaze.  Idk if that makes a difference, or not.  I am a wheel thrower, and I typically throw thin.  Don’t know if that matters, or not, either!

I realize that glaze firing in particular can vary based on the desired effect, but I’m looking for a basic framework to start from.  Based on my small test fire (only brought the kiln up to about 900-1000*, empty, to decide if I need one burner or two) my biggest fear is that the temperature will rise too quickly, and the heat stress will cause issues-up to and including cracking/exploding.

Thanks!

Amy

Shouldn't be much exploding happening in a glaze firing, but when I was firing my small raku kiln I would candle it with a smaller blowtorch just barely going, this would keep it around 200 degrees which let things dry off and get warm before I lit the big torch.  

As far as schedule goes, check the Bartlett v6-cf firing schedules.  They're an electric schedule but you'll be able to see the general trend on how quickly you should aim for.  Firing taking between 7 and 9 hours for cone 6 glaze.

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Have you been firing in electric kiln before?

If so try to acheive that temp rise if successful with your ware.

Photos of your set up, your flues , burner port, up or downdaft ,and regulators etc will help folk give you the answers which will help.

Cones all over your shelves would help indicate hotand cold spots.

 

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8 hours ago, AmyJM said:

I realize that glaze firing in particular can vary based on the desired effect, but I’m looking for a basic framework to start from.  Based on my small test fire (only brought the kiln up to about 900-1000*, empty, to decide if I need one burner or two) my biggest fear is that the temperature will rise too quickly, and the heat stress will cause issues-up to and including cracking/exploding.

Thanks!

Amy

Liam is correct, warm slowly to 200 degrees to make sure everything is dry and then typical glaze firings are 400-600 degrees per hour with the last 250 degrees or the firing being about 120 degrees per hour. 
The last 250 degrees is where your glaze will mature and if you use cones your pyrometer and the published temperature for your cone will match reasonably closely at this firing rate.

Most gas firing folks use a log as they fire and this can help display how fast you are going by doing the calculations for you. It will also get you thinking of what to log and help you get a feeling for how your kiln performs. We have several versions created in excel, open office, google sheets and numbers (iOS) that you can have to use or personalize. Message me and we will get you a copy.

Finally to raise the temperature of your kiln is simply to turn up the gas. One little issue here, as you turn up the gas say 10% the actual heating ends up more than 10%. The relationship is not linear it is exponential. I bring this up because your first few firings may surprise you how fast your kiln can go early on in the firing with very minor changes of the gas. Again something you will learn after a few firings and the log can help a bunch here as well.

below I have a screen shot of the excel version and the numbers version. When I have my iPad I use the numbers version. They all  display your speed per hour as you enter the time and temperature. The iPad version has graphs on separate tabs (last picture)

A373097B-301F-44A3-8494-D0A8AA5C75BE.jpeg.77df982e1e549d35295c4b76b8b81e95.jpegF7BF3EA4-B9C4-486D-87B7-37A0D056C7AE.jpeg.088c9490273206773dd4d38f88b0f94f.jpegFEE3AF78-A8B5-41B8-A80C-5E0D9C5AA64B.jpeg.bb91f77f8a477c566bbd1c372d409079.jpeg

 

 

Edited by Bill Kielb

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