Can anyone tell me kiln firing time?

Question

I want to fire my greenware tomorrow, haven't done it for awhile and cannot remember the exact time, etc. on firing, opening, etc. Can anyone please refresh my memory? There are no glazes in this batch, just straight greenware.

Answer 1

Q. What is greenware?
A. Greenware is the term given to a molded piece of clay after it is removed from the mold. It is generally grayish in color and extremely fragile. It is not green in color but rather, "not mature", as it has not been fired yet...thus the term "greenware".
Q. What temperature should I fire my greenware and/or glaze to?

A. Greenware is typically fired at Cone 02 - 05 depending on the type of finish being used. If the piece is going to be glazed then the Cone 02 - 04 temperatures are better. If the piece is going to be decorated with a non-firing product then the Cone 05-06 temperatures are sufficient...however if you are uncertain at the time of bisque firing then it is better to fire to the hotter temperatures (Cone 02 - 04). The non-firing finishes can still be used on the hotter fired bisque but may not absorb as easily into the "harder" bisque. The fired finishes, such as glazes or the "underglazes for bisque" will work better if applied to a bisque that is fired hotter thus allowing you to fire the glaze at a cooler cone (05-06).
www.adobiceramics.com/FAQ'S.htm


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How to fire
By Steven Wilburn, ex-fireman for NMclay.com.

Firing your manual kiln

Before loading your kiln be sure that it's not near anything combustible as the exterior becomes very hot. Most kiln companies recommend a 12" space between the kiln and the wall.
Loading your kiln
It is important to have a shelf in the very bottom resting on three 1" posts in a triangular arrangement. This allows air to flow under the ware and give them even heating. If additional shelves are used be sure that the posts supporting them are placed directly above the original 1" posts located under the first shelf in the bottom. This prevents warping or cracking.
Determine what type of firing you will be doing. Clay or greenware being fired for the first time will require what is called "bisque" firing. This will remove carbon and other impurities that can cause problems in glazes. It also hardens the ware so that it can be handled and glazed more safely. Place your pieces in the kiln according to like sizes in order to increase efficiency of space. It is a good idea to put shorter pieces at the bottom and taller pieces at the top because tall posts tend to fall over easily, sometimes breaking things. Arrange your artwork evenly in the kiln to allow airflow to pass between everything, be especially careful not to have glazed pieces touching each other or they will stick together. Glazed ware needs to be at least 1/4" apart as when they are heated they can expand and touch. It is a good idea when firing glazes to have a thin layer of kiln wash on the shelves so that if glaze drips on them it can be easily removed. Also remember to put stilts under pieces that are glazed on the bottom to avoid sticking; this can only be done in low fire. Stoneware or porcelain pieces need to be dry footed (no glaze on bottom). Always be sure to use the proper cone for the type of firing you are doing and avoid the confusion commonly associated with cone 06 (low fire) and cone 6 (high fire). Always read labels on products. Manuel kilns require a bar cone in the sitter so that the kiln will shut off at a specified temperature, this temperature is determined by a cone number marked on the side of the cone (cone 06 approx.1830F,cone 04 approx.1940F, cone 6 approx.2232F). Digital kilns don't require a bar cone but it is important to use witness cones to determine if the kiln fired correctly. Slip cast ware or relatively thin walled hand built items can be fired on a medium to fast speed schedule, thicker pieces should be fired slowly. Digital controllers have pre-programmed schedules for different speeds (Fast-Fst, Medium-Med, Slow-SLO)
A good schedule for firing pieces that are thin:
(1/8") to medium (1/4") in a manual kiln is- 1. turn switch(s) to low for one hour, 2.go to medium for another hour, 3.then to high where it will stay until firing is done. After the firing is complete let the kiln cool till it is nearly room temperature, lifting the lid too early can cause cracking or damage to the kiln. If an explosion occurs during the firing, (usually due to air pockets or moisture), it is important to remove any fragments that may have fallen into the element grooves. Clay or glaze touching the elements will cause them to burn out. Sometimes an explosion can cause the sitter to get jammed, if this occurs the kiln will not turn off and the contents will melt down (total disaster). Don't be discouraged, many kilns come with a built-in safety timer that you can set for the estimated firing time, this will vary depending on the size of kiln and the density of the load. When the timer reaches 0 the power to the kiln will shut off. It is important to set the timer for more time than the firing takes, if the timer turns the kiln off before the sitter does, than the firing has not been completed. If this happens you can simply re-fire the load being sure the timer is set for more time than before. If your kiln doesn't have a timer you should check it when it should be turning off. If it goes a whole hour past the it's usual time then turn it off by hand and examine the ware and the sitter when it cools off. This is another good reason for using witness cones. Make records of your firings so you can get to know your kiln better, if you notice the results changing than it may need an adjustment or new elements.
http://www.nmclay.com/Customer_service/
Howtofire.htm

Answer 2

I won't even try to match such a long answer for most details. But felt the need to make a single point.

Clay ceases to be clay (will get wet and slump etc) at what is called the metasilicate point. This temperature is around 850 F which is very much lower than noted above.

Now a kiln is not the same temp everywhere, and higher fired ware is stronger than lower fired ware, but even porcelain can be fired to cone 017 1200F-1500F, and then glazed for the second firing.

It is very slightly more fragile, but one should take care in any case, and you can save a lot in time and money by not making the ware go so high. The glaze will also set in deeper in a more porous clay than one less so.

Answer 3

Use the Donald Trump method..."You're Fired!"

Answer 4

What Is Greenware