lime mortar with perlite part 2

The sample has been kept wet for a week.

Yesterday I broke it in two and put one part in the. now heated, defunct wet freezer.  The other half was allowed to dry for a day then baked in the electric furnace.  Currently it is on its way from 550C to 750C.   I am not following an exact firing schedule.   Cooked of the water with temperatures below 100C.   One hour at 50, 75, 90,   Then one hour at 150, 250, 350, 450, 550, and 750.

For kicks and giggles I measured the oven temperature rate of change.  Came out to about  1C in per 10 seconds.  So about 2 hours from freezing to 700C.  But this is sort of useless in that the test tile have very little mass.  This is the time for an empty oven. It also assumes that the temperature climes at a fixed rate which is not true.   As the oven gets hotter it looses more heat.  But since this was done at the upper end of what I normally heat to it might be shorter.

And I turned the controller up to 800C.  Going to turn it off in two hours.  Let the oven cool with the door shut overnight.  Examine the tile in the morning.

My friend at Chirpy's Tinkering suggests adding 1 part talc to this mix.
"in very small amounts, it'll lower the vitrify temp, but in larger amounts, it takes the melting temp way up some clays react to it in different ways, but usually talc is used in pottery to change unknown clays with low melting temps to something more managable"

"I thought sodium silicate crackling was pretty cool but I believe the one guy made some refractory out of sodium silicate, sand, talc, and bentonite, and made a hot face to go over it with sodium silicate and talc, and he was doing brass castings for quite a long time with a propane burner, and the lining seemed to hold up pretty well"

Oven turned off 800C @ 10:50PM
                            90C @  3:15AM

Its morning.

And a video summing this up.