The only thing required is to know how thick the firebrick should be and the diameter of the firebox, this can be done in the same manner using plastic to make the radius pieces (sometimes cutting some old five gallon buckets and then bending works well) and then super gluing sides onto these radius peices and then cutting off the sides to the proper thickness firebrick you wish to achieve.
In most cases to make the full cylinder will require 3 peices for easy removal from the molds as well as making absolutly sure you can get them into the door or through the top of whatever stove your working on (this can be increased to as many peices as needed to achieve your full cylinder and to insure you can get them into the stove).
with these molds its as easy as mixing up some rutland (I do not suggest going out and buying commercial genric refractory unless you know a lot about cement and coal stoves). Mix up your cement to a stiff enough consistancy to hold shape in the mold (oil the mold first with a brush and some motor oil or whatever is handy for ease of poping out the dryed casting), If you slip up and mix up the batch to wet let it slake in a bucket for awhile to stiffen up better before slopping it into the molds, you then can use an old shingle or thin strait metal to press down and sweap across those top edges of the molds (as I mimic doing in one of the photo's below to ensure no air pockets and to smooth the outer edge of the firebrick). Also note the removable end caps in each mold (these tap out after the firebrick sets and makes removal of the dryed firebrick very easy).
After you pop out your new firebricks the next day, place them in the oven at 300 for a few hours to cure before cementing them into your stove.
My molds are made of thin gauge steel so they will last a lifetime but again... they can be done in plastic as well. I used to have only one mold but made a couple more because I wanted a complete set to make the full cylinder in one swoop
Hope these photo's help give some idea's for others to assist them in making firebrick for their own stoves in the future!
