Yes, I was struck by the length of cooling as well. A year sounds like an arbitrary period, but seems long.
I mean, assuming the glass starts at like 1000 degs, (I have no idea) that means cooling about 2.5 degrees per day. Which I assume means inside an active furnace.
The additional energy, and hence cost of the finished glass but have been massive.
Presumably they learned this would be necessary from the test piece, which presumably cracked at some point.
> I mean, assuming the glass starts at like 1000 degs, (I have no idea) that means cooling about 2.5 degrees per day.
It's relevant to remember that this is a gradient tempreture throughout the mass that declines and not a uniform fall throughout.
An analog might be to think of a porous spongy material (clay, heavy peat moss, etc) and water .. annealing is the process of slowly leaching out the tempreture (or water) with no abrupt gradient changes that lead to cracking.
As the temp. in the annealing furnace is staged down, there must be a pause to allow the heat to flow out from the mass centre to match the furnace before the next reduction.
> Which I assume means inside an active furnace.
Ideally a very well insulated furnace so that little energy input is required to maintain the desired furnace mean.
I haven't read this through thoroughly, but a lot of the final polishing must have been done after it was in place. It was only moved from Pasadena to Mount Palomar in 1947. There is both a '47 and '49 as being when figuring was done. https://sites.astro.caltech.edu/palomar/about/history.html
I mean, assuming the glass starts at like 1000 degs, (I have no idea) that means cooling about 2.5 degrees per day. Which I assume means inside an active furnace.
The additional energy, and hence cost of the finished glass but have been massive.
Presumably they learned this would be necessary from the test piece, which presumably cracked at some point.