Questions and Answers about Digital Kilns
by Marci Blattenberger

 Question: I thought that buying a digital electronic kiln I could avoid buying cones but it seems I need to use them also.

  NO, you shouldnt need cones if you have a computer controller....You should just be able to follow the directions that  came with the keypad controller and punch in either the cone you desire or the temp.....
The confusion might come in because when we talk about firing temperatures, we generally refer to cones instead of temperatures...This is kind of a shorthand....a cone is clay-bodied product that is made to bend at a speciific temperature, so if you put an 017 cone into your kiln, it will bend over when the temp inside the kiln reaches that temp....
So there are devices like the computer controllers and pyrometers that fire without the physical use of cones....but we still refer to the firing temps in cones instead of degrees.( To see what the cones equal in degrees, there is a cone chart on our PPIO website that makes the convenrsons in both Farenheit and Centigrade. . (Go to PPIO.com or Porcelainpainters.com ...click on the library page, then on the cone chart...) .

Dont let a computerized firing controller intimidate you.........All you have to do is punch in the cone you want, the firing speed ( I leave mine on HIGH) and leave the HOLD on 0....There are probably more options than you need to worry about......like ramping , and holding ,etc
( The computer controller has options like ramp speed  which takes the kiln up at a specific number of degrees in a specified length of time ( eg. 10 degrees a minute ...which is useful to glass fusers )....and holding, which lets you hold the kiln at certain temps for specified amounts of time, which is also useful for glass firing but not needed for china firing......however, several artists are now extolling the virtues of firing with a hold time at the end of the firing cycle, (SOAKING) which "opens" the glaze even more and helps mature the paints , resulting in a greater shine and more clarity of color. More about "soaking" a little later)

 Question: I have no idea what temp to fire what, and what I can fire together and not together!

       You have a pretty wide lattitude in china firing...anywhere from an 018 to an 014 ( and some fire even hotter than that).......My personal preference is to fire  to an 015 ..It gives a nice reglaze to the piece and matures all colors beautifully...If i have to go more than 3 fires on a piece, I then back it down a cone a fire.....
However, note that I am talking here about firing porcelainwhich has a relatively hard glaze. If you are firing a softer glazed ware, such as Bone china, English china, ceramics or domestically (USA) produced ware ( Lenox ,Mikasa and Pickard, for example ) , you should fire at a lower temperature ( 017- 018) Firing this type of ware at a hotter temp risks bubbling the glaze and having the piece stick to your stilts.
You can fire any overglaze things together in the same load: for example, you can fire pieces that  have china paints, gold, luster, structure pastes , ( Including  structure with dichroic or other glass embedded in  it ) and enamels  in the same load ( either glazed pieces or bisque) and slumping or fusing glass.....The only time you would need a seperate firing for pieces is if you are firing glass that you dont  want to slump or fuse ...like glass lamp shades or any glass that you want to stay in the same shape you put it in the kiln as.....( wine glasses etc...) these require a cooler fire (022)
.....on the other hand, if you are pouring slip , hand-building pieces from raw clay and doing glaze firing, that all requires a much hotter fire than our chinapainting fires.......( from an 03 to a cone 8 or hotter)( FYI: the cones that begin with "0" are cooler  the higher the number goes...that means  an 022 cones is cooler than an 015.....but the un-"0"-d cones  get hotter as the numbers go up.( eg. a cone 9 is hotter than a cone 3 ......which , in  turn, is MUCH hotter than an 022...Clear as mud? heeheee.take a look at the cone chart and it will be self-explanatory.)

How I fire my computer controlled kiln:(assuming a load of porcelain )

     Load 'er up, ( put stilts under thick or large pieces), prop the lid a little and set the controller....
My large kiln is an Olympic and heres how I set my controller: ( yours might be a little different)
1. flip the ON switch on the side of the controller
2. the display will read  "IDLE"
3.press the star button
4. the display will show dashes
5. press star again, then the 1 button on the keypad ..this is where you set the Cone number....note: yours might be different)
6. punch in cone number using the keypad ...DONT FORGET TO PUT AN "0" IN FRONT OF THE NUMBER ...eg..015 .....( if you DONT put the ) in, the controller will read it as a ceramic or pottery fire and fire too hot for overglaze firing)
7. press star again ( this cycles to the speed setting...
8. on my kiln, if you want FAST , you punch 1, med 2, slow 3......I generally leave it on 1 even with large or thick objects since my kiln is pretty large and takes a while to get up to temp anyway......most of the time, youre safe firing hot right off that bat....
9.  press star again ...this cycles to the HOLD setting .
10. I leave the HOLD setting at 0.00 ( this is generally used for glass fusing and slumping to keep the kiln at a certain temp....called SOAKING..but is not necessary for china firing...but see note below for information on SOAKING)
11. press star again.....the display will read IDLE again
12. then I press star till the display reads START.....
   The kiln should turn itself on at this point...and the display should start showing the temp inside the kiln( mine makes a clicking noise when its on....yours might not)
  Leave it  for about 15-20 minutes..this should be enough time for the oils to burn out .then close the lid and let the kiln complete the firing......
  The kiln should shut off automatically when it reaches the cone temp  you punched in
   At that point, I sometimes just shut off the switch to the controller...or sometimes I press the # key , which will change the display from a blinking display( cant remember what it says..it might say something like "end" ) to a blinking display that flashes the temp inside the kiln.......
  The scariest part of firing  is doing it the first time.After that, you'll see that you were worried for nothing! (grin!) ( but if it makes you feel any better, I m currently experiencing "pouring paralysis"...heeheee I ve had 2 vase molds sitting here for over a year that Ive been wanting to pour and am worried about screwing them up..so I havent poured them yet...so I know how you feel......

A note about SOAKING (HOLDING)

I mentioned earlier that several artists (most notably Barbara Ramsey-Snow) are advocating doing a hold at the end of a firing cycle. This simply means that , instead of shutting off the kiln when the internal heat reaches the desired temperature, you hold the kiln at the peak temperature for an amount of time ( 5 to 20 minutes ) in the same manner that a kitchen oven stays at the optimum cooking temperature . The hold cycle results in a greater shine and more clarity of color but was difficult to achieve before the days of computer controllers. ( It used to mean that , when the kiln reached the desired temp, you had to leave the kiln on but raise the lid to let the temp drop, then close the lid again to raise the temp, then open the lid again to drop the temp, ad nauseum!
With a computer controller, when you program it at the beginning of the firing cycle, you simply program in your desired hold time and the kiln will automatically hold the firing temp at the desired range for the specified amount of time...and then at the end of the soaking (hold) cycle, it will shut off.
Again, this is not a needed step but it is one that gives great results...and although at the time of this writing,I have not yet tried it, I plan to do so on my very next kiln load.
marci

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