Chuck Sherwood wrote:
OK, I got a vacuum pump and I found a 1/2 gallon bell jaw at Fisher
for $42. I didn't see a base so I am wondering about making one.

I figure an aluminum plate would work fine. How thick of a plate
do I need for a 1/2 gallon bell jar? Is 3/8 enough or do I need
to go to 1/2 ?

I'd go with steel of 1/2" or thicker simply because I've never seen the base of a bell jar made out of anythign that wasn't thick steel. Al might flex and break your seal or chip the bell jar.