Ceramic Firing Kiln Prep, Kiln Schedules, ceramic firing programs for low fire, mid range and high fire ceramics.
Always do a TEST FIRE in your brand new kiln BEFORE you fire any pottery - READ BELOW to learn more.

 

 

Important Reminders

1) Always use cones on the kiln shelves so you know what temperature you are getting on the shelf.
2) Always slow fire greenware to bisque.
3) Always fire glazes at medium speed.
4) Always read glaze directions for proper application.
5) Fire kilns only when you are able to be there at or about the time the kiln should finish firing.
6) Take care of your kilns by following recommended manufacturer instructions.

 

 

The Basics of Using Clay - Kilns – Glazes – Cones – Firing

 

 

Kiln Furniture Prep

Read your kiln manual(s) first.

Kiln Wash - This layer of protection prevents glaze from sticking to the shelf when it drips from a piece of bisque.  With the coating of kiln wash on the shelf, the glaze can be scraped off easily.  The powdered kiln wash has an unlimited shelf life so it can be stored and used later. Once every six months to a year, or more if your shelves show unusual wear, scrub off the wash and apply fresh wash.

Mixing up kiln wash - Make kiln wash using ¾ cup water and adding several tablespoons at a time of powder kiln wash INTO the water (not the other way around!), mixing with each addition of powder, to form a very thin creamy paste the consistency of heavy milk. Yes, you may have to add more water, as well, especially if you are mixing up more than one bag of wash and kiln-washing more than 8-10 large half shelves.

Use a dedicated KILN WASH brush – a 2”-3” synthetic bristle brush and apply one solid coat to one side only of kiln shelves. Take the wash out to within ¼” all around the edges of the shelves. Allow shelves to dry.  Store extra kiln wash in marked, airtight container for future touch ups and use. 

 *Store shelves kiln wash sides to each other.

 

 

Loading and Unloading the Kiln

 

Set the three or four shortest posts (1/2 or 1” inch) in a triangle pattern if using half shelves or a square pattern if using full shelves inside on the bottom of the kiln.

Set shelf on top, with kiln wash side up. If 2 half shelves, leave 1/2” space between shelves for air flow.

Always use cones – more details on this in each below section.

Always log firings on Log Sheet. If ANY piece has a problem, always save cones and be sure to designate shelf they came off of for reference.

Always read Firing Sheet to be sure you are properly pushing the correct buttons for a firing. Always press Program Review to make sure you did indeed push the correct buttons.

Never turn the kilns on if someone is not going to be at the house or studio at or about the time the kiln should turn off.

Never turn the kilns on if in the middle of a storm and the electricity continues to go on and off.

Always stilt glazed pieces with low fire pottery.

Always leave 1” space between pieces.

Always leave 1 ½”  - 2” space from top of tallest piece on any shelf to shelf above it.

Always check stilts to be sure pins are free of glaze from previous firing and are still straight up.

Always check stilts when unloading. Use stilt stone or Dremel off any glaze – be sure to wear safety glasses when doing so.

Always put correct posts and stilts back in their corresponding bins.

Do not take cones out of boxes until you are ready to use them. Always keep cone boxes closed when not in use.

After turning on kilns, if venting, flip in-line switch on vents to turn them on during firing.

*Watch out for the thermocouple – DO NOT BUMP IT WITH THE SHELVES WHEN LOADING AND UNLOADING THE KILN.

 

 

Test Fire - There are 4 reasons to do a test fire in your new ceramic kiln BEFORE you try to fire bisque or glazes:

1. To oxidize the elements. This is also sometimes called ‘seating the elements’ firing.
2. To temper the shelves, posts and sometimes stilts.
3. To make sure the wiring was done properly and to make sure the kiln is getting the power it needs.
4. To find out the firing personality of the kiln. All kilns, just like all ovens, have some slight variations to the way they fire. Might be a bit hot, or a bit cool. Can have hot or cool spots. Can be a cone cooler on the bottom shelf.

After loading the kiln, as per above instructions, we test fire most ceramic kilns to Cone 04, medium speed. There are SOME kilns that can not fire to 04 at medium speed. You will use a set of cones - Cone 03, 04, 05 - on each of the layers. If a medium sized kiln, it may be we only put the cones on the bottom shelf and on another layer of shelves ABOUT half way up inside the kiln. Again - remember to load shelves an inch and a half to 2” ABOVE or BELOW the thermocouple. If a large 10 or 12 sided kiln, you may have anywhere from 4 to 5 layers of shelves. You will want to have a set of cones on the bottom layer, up a third and up another third. If there are other layers in between these, it is not necessary to also put a set of cones on these shelves. Some manufacturers may suggest putting an 04 cone also on a shelf closest to the thermocouple. You can do this but the other sets of cones should be placed towards the center of the kilns. We know the temperature will be hotter closer to the elements, but we need to know what the temperatures are getting to in the center sections of these kilns. If we find the bottom is firing cooler than the other sections, then we will want to add a HOLD time to the glaze firings. This may or may not be necessary on the high fire side of firings. If the bottom shelf is cooler, your oranges and reds may not mature and may be brown or not quite bright enough for you.
Do check out the Orton 3 Cone System and Understanding Cones and Temperature on these pages on our site.

 

 

Firing the Kiln - Clay Firing – turning Greenware to Bisque:

Greenware pieces are not stilted. Doing so will melt the clay body into the stilt.

Place one each of pyrometric self-supporting cones 03, 04, 05 in the middle of the bottom shelf 1” apart in a row and 1” apart from one another. Place 3 posts* in a triangle pattern on each of the 2 half shelves. Continue to load shelves, posts cones and pieces making sure the tallest piece on any shelf still has a 1 ½” clearance to the shelf above it.

Make sure that any shelf will be either 1 1/2” - 2” above or below thermocouple.
Close lid.

Make sure peephole plugs are in the peepholes.

Follow directions for pushing buttons on kiln. 04, Slow Speed, No Hold.

*Clay – firing greenware to bisque to 04 firing, thus the 03, 04, 05 cones.  Temp goes DOWN with higher “O” numbers; goes UP with regular numbers. 

In this clay firing, the 03 cone should stay standing, the 04 bent over between 3 o’clock or to a perfect touch at “6 o’clock”, and the 05 should go limp and look like an elephant trunk.

Temp will be 1940 to 1945 degrees F.  Firing will take 9 to 10 hours or longer depending on size of kiln and how full the load is. Do not go home until the kilns have completed firing.

Low Fire Clay Bodies like Laguna Terra Cotta EM215 and EM 210 White may say 04-06 on the box they come in. This means fire the clay to 04 (AROUND 1940-1945 degrees F.) to turn it from greenware to bisque. You do THIS 04 firing on SLOW speed. And then fire the low fire glazes to 06 (AROUND 1830-1835 degrees F.) You do THIS firing on MEDIUM speed.

The low fire clay body can then be painted with our low fire paints and then dipped (or not), stilted and then fired to 06, medium speed.

High Fire Clay Bodies can be Cone 5, Cone 6, Cone 8, Cone 10 Stonewares or Cone 6 Porcelain. These boxes may only say Cone 5 or Cone 6 or Cone 10 or whatever temperature that clay body MATURES at. To turn this greenware clay to bisque, you still fire 04, SLOW speed. Some people will bisque fire to Cone 06. But you do the GLAZE firing to the temperature or cone indicated on the box. See below for more details on greenware to bisque firings and glaze firings.

 

 

Firing the Kiln - Firing Low fire Pottery after Dipping:

Place one each of pyrometric self-supporting cones 05, 06, 07 in the middle of the bottom shelf 1” apart in a row and 1” apart from one another. Place 3 posts* in a triangle pattern to place half shelf.

Stilt pieces allowing 1 ½” from top of tallest piece to shelf above it.  Lay down next layer of shelves.

Continue to set posts, stilted pieces and shelves until you have fully loaded the kiln.

Be sure any shelf is at least 1 ½” - 2” above or below the thermocouple. If at all possible, be sure no shelf is lined up exactly to block elements in grooves.
Close lid.

Make sure peephole plugs are in the peepholes.

Follow directions for pushing buttons on kiln. 06, Medium Speed, Designated Hold.

*Low Fire Dipped Pottery – firing pottery to 06 firing, thus the 05, 06, 07 cones.  Temp goes DOWN with higher “O” numbers; goes UP with regular numbers. In this clay firing, the 05 cone should stay standing, the 06 bent over between 3 o’clock or to a perfect touch at “6 o’clock”, and the 07 should go limp and it will look like an elephant trunk.

Temp will be 1830 to 1835 degrees F.  Firing will take 7 ½ to 8 hours or longer depending on size of kiln and how full the load is. Do not go home until the kilns have completed firing. Unload at 100 degrees or room temperature.

 

 

Firing the Kiln - High Fire Clay Bodies:

Cone 5 clay body - fire greenware to bisque at 04 slow speed, then to Cone 5 medium speed for the glaze firing.

Cone 6 clay body - fire greenware to bisque at 04 slow speed, then to Cone 6 medium speed for the glaze firing.

Cone 8 clay body - fire greenware to bisque at 04 slow speed, then to Cone 8 medium speed for the glaze firing.

Cone 10 clay body - fire greenware to bisque at 04 slow speed, then to Cone 10 medium speed for the glaze firing.

*Yes, some people will fire their mid range or high fire clay bodes to Cone 06 or Cone 08 when turning green ware to bisque. Slow Speed.

 

 

Other Glazes:

Some Mayco glazes can go BOTH high fire and low fire.

Most Amaco glazes are designated to go EITHER low fire or high fire. SOME can do both. Read the label.