Some continued boiling after removal is fairly normal. I usually let them sit in the canner for a few minutes after removing the lid until the activity settles down.

However, a couple of questions for you. 1) why 15 lbs. that is far more than normally required or is this a weighted only canner at high altitude? If you are high altitude then more bubbling activity is common.

2) 8 qt pressure canner? Most all 8 qts are pressure cookers only, not canners. Will this one hold 4 quart jars at a time?

Dave

There is a wait time after processing. For pressure canners it means allowing the pressure to drop to zero, removing the pressure regulator and then waiting 10 minutes before removing the lid and lifting out the jars. This wait time reduces the likelihood of siphoning of liquid from jars. The contents may still be boiling, but not nearly as much.

Also, as Dave said, to be designated as a pressure canner, the vessel must accomodate 4 1-quart jars; generally a 12-quart is the minimum size possible. The time to come up to pressure and then back down to zero is much less with a smaller canner, thus resulting in a shortened total processing time. With low-acid products like meats this can potentially be dangerous.

Carol

>> 1) why 15 lbs. that is far more than normally
>> required or is this a weighted only canner at
>> high altitude?

I am at an altitude of 1325 feet. The table for weighted-gauge pressure canner clearly shows that I should use 15 lbs. for 15 minutes.
http://www.uga.edu/nchfp/how/can_03/tomato_juice.html

>> 2) 8 qt pressure canner? Most all 8 qts are
>> pressure cookers only, not canners. Will this
>> one hold 4 quart jars at a time?

This is an older model Mirro M-0598 weighted-gauge pressure cooker and canner. I got it second hand but it came with the original manual which includes pressure canning instructions and shows that it can be used to pressure can 4 quarts or 7 pints. It works well for me because I often just can small batches. The main drawback to this size canner is that I can't use it to do BWB canning on quarts because it's not deep enough to cover the quart jars with water. But if I'm doing BWB it's usually for salsa or jelly which I do in pints or 1/2 pints anyway.

Yeah, like I said above if you have a weight-only canner then you can do it for 20 mins at 10 lbs. or 15 at 15 lbs. If you had a dial gauge you would only need 6 lbs. at your altitude. Either way your jars are good.

Dave

It sounds like you are relying upon an out-of-date manual that does not correspond to current standards. Generally canner manuals are re-printed year after year and are seldom updated.

Also, the fact that Mirro calls their pressure cooker a canner doesn't mean that it really qualifies as one. They have a vested interest in selling their product to the largest possible audience.

Are you sure you were looking at the correct section of the NCHFP chart? For a weighted-gauge canner processing is not recommended above 1000 feet.

Regardless, it's your call whether you use this pressure cooker or not. All we do is try to clarify.

Carol

Two of the most experienced self-sufficient gardeners I know use blacklisted canning equipment. One uses a steam canner (can't buy those anymore) and another uses a small 4-quart pressure cooker like yours. Just sayin.

The only thing I pressure can is soup mix, and it keeps boiling in the quart jars for a long time. I think that's why you leave more head space when pressure canning.

>> It sounds like you are relying upon an out-of-date
>> manual that does not correspond to current standards.
>> Generally canner manuals are re-printed year after
>> year and are seldom updated.

No, as mentioned above, I am using the current NCHFP guidelines, NOT the table in the old outdated manual which says I should use 5 lbs. for 10 minutes.

>> Are you sure you were looking at the correct section
>> of the NCHFP chart? For a weighted-gauge canner
>> processing is not recommended above 1000 feet.

Actually, I don't think that you are interpreting the chart correctly. As I understand Table 3 it says that over 1000 feet one should use 10 lbs. of pressure for 20 minutes or 15 lbs. for 15 minutes but NOT X lbs. for 10 minutes.
http://www.uga.edu/nchfp/how/can_03/tomato_juice.html

------

I believe I'm now starting to understand the scientific explanation for my original question. Normally when you remove a small boiling pot from it's heat source it will stop boiling almost immediately because the temperature of the contents will quickly drop back below 212 degrees and since the atmospheric pressure stays the same it stops boiling quickly. As I am using the higher recommended pressure of 15 lbs, the temperature of the tomato juice is reaching 250 degrees. When I remove my pressure canner from the heat it's temperature drops quickly because it is a relatively small canner which doesn't need much water (1.5 qt) for pressure canning and there is much more air (~7 qt of air) than water. So the pressure canner cools and unlocks and I remove the jars. In the jar there is only a tiny, tiny amount of air which cools quickly and contracts creating the necessary vacuum to seal the lid. But the liquid is still very hot and now the pressure (vacuum) inside the jar is well below atmospheric pressure so the jar continues to boil even though the temperature of the liquid may drop below 212 degrees.

- Steve

Steve, I have the Mirro M-0598 and the book that came with it does call it a pressure canner. It even says 'canner' on the original box - and I used to use it for canning pt jars when I had those odd two or three left over from doing big batches in my 22 qt canner.

But with the perforated canning rack in place, the lid is about an eyelash shy of closing on 4 1-quart jars, that means it no longer meets guidelines for safe pressure canning. I didn't ever have any problems with things canned in it, but to stay on the side of safety, I now use it only for cooking food.

Please don't go by those old manuals, the instructions in them are often dated. None of mine mention venting, now a requirement for current canning guidelines, and the processing times have changed on some things too - like fish, tuna.

Steve's right on the NCHFP chart.

20 mins at 10 lbs. or 15 mins. at 15 lbs.

But 10 mins. at 15 lbs. is only for 1000' and not recommended for above 1000'.

Steve - also keep in mind the temp of boiling at higher altitudes and When I remove my pressure canner from the heat it's temperature drops quickly because it is a relatively small canner which doesn't need much water (1.5 qt) for pressure canning and there is much more air (~7 qt of air) than water. is the reason why those small ones are no longer recommended. The normal required heat up and cool down time is used to calculate into the published processing times. The small ones heat up and cool down mush faster so it skews the processing time calculations. But as morz says, some still use them and with tomato juice I wouldn't be concerned. Other really low acid things like meat and vegetables might be underprocessed though in that small canner.

Dave