Newbie Firing Questions

[Pat B.]

Hi All,

Questions from a newbie. I've tried to find the answers to them, but all the info I find is generalized and my questions are pretty specific.

I have an L&L e23s-3 electric kiln in an unheated shed with a vent-sure downdraft vent. It is very cold right now in upstate NY so I'm on hold with the firing until things warm up a bit.

Question 1: Should I bisque fire to cone 04, or is cone 06 high enough for Laguna 55 WC607 clay? I plan to glaze with commercial glazes at cone 6, most commonly a clear one (The Ceramic Shop C656D).

Question 2: Does staining the clay with mason stain affect what the bisque temperature should be? I know dark clay needs a hotter bisque than white stoneware to burn off stuff, but what about white stoneware that has up to 10% mason stains mixed in? Most pieces will be 4% or less, but a few will be up to 10%.

Question 3: I plan to do a pre-heat on the bisque fire to drive off any water, but does the glaze firing also need a pre-heat?

Question 4: Should I do a controlled cooling on the glaze firing given that it's so cold outside here?

Question 5: Should I turn off the downdraft vent as soon as the firing cycle is complete? What if I do a controlled cool, should I leave it on then?

Your help is appreciated.

[Bill Kielb]

Q1: Most bisque to 04 when glazing to cone 6, however if you need your body to be more porous, you certainly can bisque to 05, 06 usually figured out by trial and error for a specific reason. I assume it’s a cone 6 clay here.

Q2: dark bodies often contain more organics so bisque longer to 04 not hotter is the remedy to give enough time to burnout everything. Use  the slow bisque automatic cone fire program if your kiln has it. Stains and underglazes don’t really contain organics, so no worries there. Your automatic controller will default to about 14 hours for a slow bisque. For a very dirty dark clay, longer may be needed but this is a fairly long schedule already.

Q3: generally the glaze fire does not contain much water so usually the answer is no. If you just finished glazing the pots and stuck them in the kiln, then yes, do a preheat to dry them out. Your automatic controller will default to about an eight hour glaze for cone six. Any preheat will increase the firing time.

Q4: controlled cooling is aesthetic preference. If it’s really cold outside vs let’s say 0 versus a nice 70 degrees you may think it’s really cold for you but your kiln fires in excess of 2200 degrees so only about a 3% change to your kiln. If you slow cooled for looks before, do it now otherwise experiment with it and see if you like the look better. 
Q5: yeah you can turn it off, save the energy, it’s not needed. Never is needed after the firing, and if it’s zero outside, not a bad idea.

As far as cold this morning, woke up to a whole bunch of snow 

[Pat B.]

Bill,

Yeah, we're going to get that snow tomorrow. I definitely have Florida envy at this time of year!

You gave me such complete answers to each of my questions. I thank you.

Pat (Potterhead)

 

 

[oldlady]

pat, controlled cooling is not a necessary step in firing.   it is used by people who have a particular glaze that might form tiny crystals in that specific glaze.    your kiln has pre-set programs that work for probably 99% of firings.   until you create some spectacular glaze recipe, just do the simple ones .   

 

[LeeU]

I have the same wonderful L&L kiln. I use commercial clay bodies & glazes. The kiln is on an unheated screen porch that has vinyl panels instead of screens.  I have fired at 8 below 0 with 2 feet of snow outside with no problem. The pre-set programs are terrific and they are all in the manual for easy reference.  I single fire/no bisque and almost always use the slow glaze program. I use the slow cool program for pseudo crystalline glazes (I like Coyote's line). I turn the vent fan off when the firing stage is complete...no more vapors at that point.  Leaving the fan running makes it cool down faster and I don't want that. I usually crack the lid around 200 just for a quick peek, but not in zero degree weather, mainly because it is too cold for me!