The shelf foam may work for de-bubbling casting investment, but will
it survive a hot casting flask?
This stuff works fantastic! It seals so well you can't pull the
bell off the table while its on, no matter how hard you pull on it.
And I had the table screwed down for the test as I had my daughters
with me today and I didn't want it knocked over and land on them.
If you want to keep students out of the “cookie” jar (i.e. vacuum
bell jar containing precious metals), you pull a vacuum on it before
shutting down the machine. Even if the bell jar leaks back to near
atmosphere, it will still hold. Why? Because 14.7 pounds of air per
square inch is pushing down on it. For one square foot of surface
area, as much as 2100 lbs force is acting on it.
I used to think that glass bell jars had metal cages around them to
protect them from damage, and to make it easy to pick them up. I
later learned that they are primarily for protection of the operator
in case the bell jar collapses. I have never seen one implode, and I
hope I never do. I prefer a stainless steel bell jar with view ports.
If you need an almost free vac gage (donate to Orchid), just email
me off list.