Saturday, October 22, 2011

Pottery Firings

Please read this before you fire EVERY TIME
My Firing Chart Bisque Firing 05 1870F - 04 1950F Approx 10 Hours
(longer and hotter for thicker pieces or packed kiln)

  1. if you have not test fired a new batch of clay you don't know what cone clay you are working with.

  2. you really can't go to slowly to bisque- as long as you do not exceed cone or temperature or time- if you need 10-12 hours to get there fineNEVER RUSH a bisque firing, never rise more than 200F per hour

  3. RAMP a bisque firing, meaning put the bottom elements or switch on low over-night before you fire in the morning

  4. 1-2 cones higher if the pieces are thicker or the kiln more packed (if you over pack the kiln the center of the kiln will misfire and will crack in Glaze firing.

  5. some critical point to certain temperature points in BISQUE fires

  • 221F water turns to steam

  • 440F the cristobalite rapidly expands

  • 517F Carbon buns

  • 1050F Quarts rapidly expands

  • 1652F Clay is strong enough to handle and is sufficiently prepared to meet a glaze fire with out problems

6. The top of the kiln is hotter than the middle, if your pyrometer (or test cone) is in the center remember the top shelf is hotter.

7. Bisque fire to cone 05 1870F or 04 1959F (as above: fire bisque load one or two cones higher if firing thick work or if kiln is heavily loaded) Note: (if you over load the kiln too much the pieces in the center of kiln will under fire or "mis" fire and likely crack during glaze firing)

  • Lower Element Switch to Low over night vented holes

  • Both Element Switches to Low a min. of 2 Hours vented holes

  • Both Element Switches to Med. a min. of 2 Hours vented holes

  • Lower Element Switch to Hi Top to Med Min of 2 Hours close vents

  • Lower and top switches to Hi to cone (approx 3-4 hours in my paragon interior 15" 2 knob kiln) closed vents

GLAZE FIRING CONE 5 - 2118F approx 6-10 hours

  1. Make sure you do not start with mis fired bisque ware or low fired bisque ware or expect cracks, crazing, crackling glaze, crawling glaze

  2. do not start with over fired bisque ware or expect crawling glaze or non adhering glaze

  3. if you over-fire glazeware your pieces will warp, crack, have sharp pin points in glaze, mis colored low colored glaze, and clay will have frogging (boiling clay))

  4. if you under fire glaze ware your pieces will look hazed as if there is a haze over the color so the color is under developed.


Glaze firing to cone 5 is rather quick

  1. top and lower switches to low with vented holes 1 hour

  2. top and lower switches to med with vented holes 1 hour

  3. top and lower switches to High plug all vents leave on to cone


  1. top and lower switches to low with vented holes 2 hours

  2. top and lower switches to med with vented holes 2 hours

  3. lower switch to hi top to med plugged vents 2 hours

  4. top and lower switches to hi with plugged holes to cone


06- 1798F ON TOP OF BISQUE CONE 04- 1915F

(yes i know! the bisque is higher than the glaze firing!) as per above glaze fire

  1. 1-2 hr each stage and then high w/ plugged vents to cone. -

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