You are correct that the guage will, if not defective, read the correct pressure whether the canner is properly vented and exhausted or not. However, that is not what we want to know. We want to know the temperature of a properly vented and exhaustwed Canner. Example: Every canner should have a temperature of 240 degrees at 10 pounds of pressure.

The 240 degrees is important because at that temperature maintained for 15 minutes botulism will be KILLED, as well as all other "germs".

I exhaust in the following manner:
1. I put hot water 2 inches in depth in the canner.
2. As I fill the jars, I place them in the canner.
3. When step #2 is completed, I place the cover on the canner and screw it down.
4. Make sure the vent (petcock) is open.
5. Turn the burner on, and to high.
6. When the steam roars out of the petcock through all exhaust holes, (about 5 minutes or so) wait for another 5 minutes and the canner is exhausted and you close the petcock.
7. As the pressure rises on the gauge past 5 pounds, begin turning the burner down so that it approaches the pounds that you will be canning at. (Usually 10 pounds).
8. Maintain the canning pressure at no more than 1 pound over the pounds the recipe calls for.
9 Can for the amount of minutes the canning recipe calls for. (The canning time begins when the pressure guage shows the pounds that you are canning at)

10. When the canning time is over, turn the burner to OFF.
11. Wait until the pressure gauge goes to ZERO then open the petcock and unscrew the lid.

Remove the jars and place them on the counter about 2 inches apart and wait for the pinging to begin.

Note: Maintain as level a pressure as possible. Variations like wavering from 10 to 15 pounds will pull the moisture from the jars. Not good.

Pay attention to the pressure gauge. Canning under pressure is absolutely safe if you pay attention to the gauge throught the process. It's not the time to make fone calls, watch tv, or cut the lawn.

Have fun.

Thats why pressure canners

I was probably the culprit (at least in part) for that remark. I was citing a source but I freely acknowledge the science behind pressure canning is not an area of expertise and I may have misunderstood what I was reading or stated the issue poorly.

Then, of course, I got busy trying to find the original source (That'll teach me not to annotate.) and in doing so found an interesting document on the University of Georgia site; it appears to be an abstract reviewing various studies of home canning equipment going back to the early 1900's.

This statement may have inspired the one I found on another site: "Since 1944, USDA has recommended that pressure canners be vented for 10 minutes prior to pressurization. A mixture of air and steam will create gauge pressure without the necessary corresponding high temperature (Esselen, 1944; Esselen and Fellers, 1950), and could result in understerilization."

johnh-gardener, thank you for the succinct list of recommendations for pressure-canner use. It's a good reminder and worth re-reading even for experienced canners who come to the beginning of the season and haven't used a pressure canner for a while.

I think one of the most important bits of advice is near the close when you cautioned to monitor pressure canners carefully.

Carol

Here is a link that might be useful: Equipment and its Management: History and Current Issues . . .

Not trying to hijack...........but.......
How does this work with the weighted canners?
The steam that escapes before the weight rocks is the equivalent of venting??

After reading all the posts here, I did re-read the manual and nowhere is there anything about venting. I assume (probably shouldn't...) that it all happens automatically with the weight?

Please tell me I am correct!
Deanna

Malon, correct!

Johnh, I am sure that you are quoting things as they are commonly stated in various documents even though they are missleading.

1. Air must be vented from a canner because air is a poor conductor of heat, leaving it in a canner can mean that the jars may not be heated properly as they would with pure steam.
2. You could can forever at 10 lbs and NEVER reach 240 deg.. That is because 240 deg. cannot occur untill you reach 24.969 lbs abs., 10 psig equals only 24.696 lbs abs. which is a little shy of the 240 degree mark. This would be even worse when canning at 1500' or so. That's why you see the canning pressure for a gauge canner stated as 11 psig.
   Why the weight is still refered to as a 10 lb weight is beyond me, must be a hold over from days past. Perhaps it was easier to say 10 lbs instead of 10.xx lb. weight.
3. Most canning gauge pressures start at 11 psig at sea level.
   Sometimes there is too much a tendancy to "round off" etc and this can cause confusion especially when it comes from a govt. agency. and it gets worse when there is no explanation as to WHY. I hate it when "someone" says "do this" and gives no reason WHY.

Deanna,
Waiting until the weight rocks IS NOT the same as venting. Venting occurs PRIOR to putting the weight in place. Old question. Regards - Jim

The reason to completely vent air is due to its compressability.A gauge will register any perceived pressure,and an air pocket could lead you to believe that an 11# reading means one has attained the desired temperature,which as Jimrbto points out above,is not the case.
True pressure/temperature correlation can't begin until a "solid" situation exists,either as liquid or saturated steam.

My fairly new All American canner was doing so well till my last batch. When doing the 10 minute venting only air came out. No steam. There was plenty of water in the canner. The petcock was not plugged. What could be the problem?

Only 2 possible explanations: either a) there wasn't enough water in it to create a sufficient volume of steam or b) the heat wasn't turned up enough to cause it too boil and steam to form. If nothing is plugged - and since air was venting there couldn't be a plug - then the most common cause it lack of sufficient water in the canner. There is a correlation between the volume of the canner, the volume of water, and the amount of time and heat required for steam to form and vent.

Dave

Digdirt, what is the ideal ratio of canner volume and water volume to achieve pressure and temp in the shortest reasonable time? The only thing I have heard, and what my manual states, is the "2-3 inches" rule. I've always read to put the water in first, then the jars, but I've never been sure of the science behind it. If you have a source I would love to look it up.

Everyone's level of comfort will be different in how closely they follow recommended procedures for safety, but USDA has recommended pressure canners be vented for 10 minutes prior to timing since 1944. More attention was given to the 10 minutes as being important in 1988. It's not new news ;0)

10 minutes isn't a deal breaker for me, I can invest that much more time each load.

Hello everyone, this is my first post.

I don't know if this fits in here, but I was wondering how quickly should my gauge on an All American No. 7 Canner drop to zero after the heat is turned off? I think mine drops to zero after about 10 minutes, maybe faster. I may need a new spout for mine, since I use it regularly (every month). I think I've had it for 10 years now.

Also, I've always let mine rattle constantly with raw chicken in jars, because I initially (10 years ago) worried that if I couldn't hear it rattle, I might not know if it ran out of water. I know they it should rattle 1-4 times per minute.

The book that came with the canner says 75-80 minutes for raw chicken, but I don't like pink chicken, so I just run it for 90 minutes.

I've canned raw pork, beef, and chicken so far. I did the adjustable weighted valve addition myself after I got it at a yard sale. It originally had the petcock valve, gauge and the "safety" valve (the safety valve was always open).

After talking to American via email, they said I could just remove the safety valve and add the spout for the weight. The petcock will release pressure at around 23 LBS, so it acts as the safety valve now (autoclave anyone?). I had to buy a tap to thread the hole a little deeper, since it wasn't thread all the way through and the spout bottomed out, not sealing well enough. I use steam-rated Teflon paste on the threads.