I have a glass top stove and just purchased an All American pressure cooker/canner. It's very heavy and will hold 7 quarts or 19 pints. If I use a diffuser will I be able to use my stove to can food?
Glass stove top manufacturers sometimes recommend not using pressure canners because the weight and heat distribution can be too much for them and the glass surface can crack.
A diffuser would probably not help with that problem. The diffuser is not likely to be so much bigger than the canner that it would distribute the weight. If it was that large then it would diffuse the heat too much.
Sometimes stove or canner manuals will place restrictions on the size of the canner vs the burner size. If the canner is too large it can transfer heat out of the burner area and damage the surface.
Another common problem mentioned is that some canners have concave bottoms. Obviously, only flat bottomed canners should be used otherwise the weight distribution will be bad for the burner and the canner might not heat properly.
You should check with the manufacturer of your range and see if your range can be used with a pressure canner. If they say it can can then you can can without the diffuser. If they say it can't then you may just be out of luck.
We use a camp stove and do a lot of our pressure canning outside- especially in the summer to save AC bills.
Anecdotally- My mother once, 20 years ago, had a glass surface crack while canning. I have been canning on a glass surface for two years without incident.
Not sure why you would use a diffuser to can food. As far as a glass top stove, it is no different for canning than gas or a electric coil top burner. As long as you have water in the pot (sufficient to water bath the jars, usually to the rim) and obtain an internal temperature of 180F. inside the jar, your there. 1/2 pint needs 45 minutes after starting to boil to reach the 180F. 1 pint needs 1 hour. 1 quart needs 1 1/2 hours after starting to boil to reach a 180F safe level. Of course pressure cookers are a whole different animal and the pot should always come with the numbers. Mike