Disclaimer! I don't stabilize, I've never put a Wal-Mart cookie jar under vacuum, and I'm not a materials scientist. However, I know enough about stress concentrations and crack propagation to be dangerous, and I caution anyone considering glass chambers to reconsider the idea, or at the very least take adequate safety precautions.
Regardless of the thickness of the glass, there are numerous potential failure modes for these containers. From cracks propagating from an imperfection, to bumping it with your watch while it's under vacuum, to vibration as you push it across your bench, the possibility of catastrophic failure is significant.
Similar to metals, glass is also subject to fatigue failures, meaning that the repeated application of stress can weaken glass, causing it to fail at stress levels way below what what a new piece of glass can withstand. These jars could work fine for a long time, then fail without warning.
I know, in the other thread on the subject, Steve points out that he's made a dozen chambers with candy jars and hasn't had any issues. That's great, but it doesn't mean it's a safe thing to do. It could mean that his chambers don't have any inclusions which might start a crack, or that they have not cycled enough times to fail from fatigue, or maybe they really are robust enough to tolerate this kind of service.
So, my advice is to avoid any material or vessel which is not rated for the vacuum you want to use. If you insist on doing this, please wear safety gear or use some sort of containment, such as putting the jar into a 5 gallon bucket prior to pulling a vacuum.
I don't mean to be a killjoy, but if it saves even one person from getting juice or blood all over the shop, it'll be worth the eye rolling you might be doing after reading this post.
