"Finger Tight"

Most canning tutorials say that bands should be put on "finger tight" before loading into the canner. That's somewhat vague and qualitative.  As I have noted (more than once), I've historically had a problem getting the right tension.  With water bath canning I eventually just started tightening them pretty tight--call it firm--and dealt with the occasional creased lids.

Even with creased lids, I have almost always gotten a decent seal, and on the exceedingly rare occasion where a jar either hasn't sealed or the seal has later failed, it hasn't been on a creased lid (this is except for the reusable lids, which I have now completely abandoned--anybody want a case of them?).

Back to what in the world finger-tight means.  When I started pressure canning, I didn't want to tighten the jar lids too much, but was somewhat nonplussed at how loose I should make them.  I found this video at the Lehman's site which quantifies how far to tighten the bands:  Screw them on until first resistance, then about one inch further.  That's what I have done for the pressure canning and it has worked (although it's apparent there is some trace leakage from the jars...the residual water in the canner has a somewhat broth-like aroma).  The overall jar fluid level seems to have been okay (but one could ask how much higher it might have been if the jars had been tighter).

This PDF (also written up here) by Frances L. Reasonover of Texas A&M suggests that in a pressurized canner, leakage should be impossible--and, indirectly, indicates why the canner should be allowed to cool naturally (a point also made in the video above).  if the weight is released when the contents of the jars are still too hot, the pressure inside the jars will force an overflow.

In the pressure canner I usually haven't had overflow, but I have found that the contents of my jars are still boiling after the pressure drops to zero--and this continues for some time after they are put on the counter to cool.  The remaining water in the canner does have signs of a small amount of fluid leakage, and when I did a batch of pinto beans, it was apparent most jars had experienced a slight overflow during processing.  However, one thing I have not (so far) seen with the pressure canner is jars overflowing as they cool--this has on occasion happened when canning acid foods, mostly fruit in syrup (even with very tight bands). That might have been because I removed them from the water too soon.