Pressure Cooker and Canner
I borrowed my dad's Canner and noticed that the bottom has gotten rounded. It won't do too much good to ask my dad if this is new, he is not picking up on these things much these days and I've never used it. I'm guessing it isn't supposed to be this way and is no good but didn't want to throw it out with out knowing for sure.
Saginaw County Michigan
I need some further information. Is the 'canner" a cast aluminum pressure canner? or a blue or white enamel boiling water bath techniques canner? What do you mean "the bottom has gotten rounded?" It would require intense heat to cause the metal bottom to get "rounded".
If you have a glass cook top to you stove, you cannot can on that stove. The glass will break and your stove manufacturer will tell you not to can on their stove.
Here is a link to the types of "canners"https://nchfp.uga.edu/how/general/recomm_canners.html