Rant about cooling.
Posted: Sat Apr 12, 2014 3:58 am
I have understood that theory of cooling, or more properly tradition of cooling comes from some charts Corning has published.
Those were based on experience with glass blowing. A difference is made between single side cooling (bottles) and double side cooling (bowls and othe open forms). Corning published values for double side cooling.
That seems to be a tradition that tables for fusing also declare double side cooling although the normal situation is that the blank lies on a shelf with great thermal mass.
Even the latest BE tables speak of double side cooling although the measurements appear fo be made in single side situation.
There are two difference between double side and single side
cooling. 1. Double side have double so much cooling surface..
2. In double sided the distance heat must cover is only one half of the thickness. As the cooling slows down in the square of distance the single side values must be four times longer.
I have seen here that people here take the face value of BE tables for single side work and succeed. Why the words speak of double side?
In casting the situation is different. The cooling surface is often small. A thick plaster silica mold is great insulator.
Then one must really estimate the distances heat must travel
in the glass.
Just now I have no access to kiln. A planned test to measure the heat transverse rates of different materials is currently not possible. Is Morganica or someone else interested to set equal rods of glass, mullite, plaster-silica and ceramics in test. Heat one end and measure the temperature rise at the other end.
Those were based on experience with glass blowing. A difference is made between single side cooling (bottles) and double side cooling (bowls and othe open forms). Corning published values for double side cooling.
That seems to be a tradition that tables for fusing also declare double side cooling although the normal situation is that the blank lies on a shelf with great thermal mass.
Even the latest BE tables speak of double side cooling although the measurements appear fo be made in single side situation.
There are two difference between double side and single side
cooling. 1. Double side have double so much cooling surface..
2. In double sided the distance heat must cover is only one half of the thickness. As the cooling slows down in the square of distance the single side values must be four times longer.
I have seen here that people here take the face value of BE tables for single side work and succeed. Why the words speak of double side?
In casting the situation is different. The cooling surface is often small. A thick plaster silica mold is great insulator.
Then one must really estimate the distances heat must travel
in the glass.
Just now I have no access to kiln. A planned test to measure the heat transverse rates of different materials is currently not possible. Is Morganica or someone else interested to set equal rods of glass, mullite, plaster-silica and ceramics in test. Heat one end and measure the temperature rise at the other end.