48-Inch-Mirror-Blank-Project

Kiln-Design-Philosophy

The kiln for the 48 inch will be very expensive unless it is built specially as an extension of the 48 inch mold. By doing this I think we can keep the cost to 1/3 of the standard building methods.

Salient Points

• Use standard cheap Home Depot Sand to form a flat plateau on which the mold subpieces can be placed

--This serves 2 purposes

• --1) allows laser leveling of the tops of the nub sub pieces so the casting nub depths will be correct and uniform. Webbing walls will have correct uniform thickness.
• --2) expensive flooring materials can be avoided. Fire Brick would run into the hundreds if not thousands of dollars, be hard to bond to one another in a fashion strong enough to maintain structural integrity and in the end sand would be required to allow the leveling process to occur. Thus eliminate the expensive part. Its not really used.
• --3) Using a stock tank at the stucture allows that the only refractory insulating material required is kiln blanket material. This is an Alumina-Silicate that is relatively cheap.

Mold Design

The refractory mold must be constructed in pieces due to its large size. The general idea is illustrated by the two photos of the scheme envisioned. Only 3 unique pieces plaster master positives need to be fabricated.

• Standard silica sand to be dropped down between the kiln inside diameter and the mirror mold outer diamater to retain mold positioning under hydrostatic pressure. Because of this it may be that we can not use a kiln with a single piece upper. It might have to have a lid if we can think of a way around this. Now amount of standard metal strapping would have strength enough to retain dimensions at 2100 degrees.