This article is from the Food Preserving FAQ, by Eric Decker firstname.lastname@example.org with numerous contributions by others.
Nothing against your grandmother, but usually you don't want to use "one-
trip" commercial jars for canning. Sealing jars with paraffin is also
counterindicated, because mold and other spoilers can slip in between the
paraffin and the side of the jar. Even a common trick of turning the jar
upside down to "sterilize" the top is not advised. [More on this below.
(Use a boiling waterbath for about 5-10 minutes instead.) Food preserving
technique "rules" tend to change every few years, due to new knowledge
about microbiology and mycology, and due to rigorous testing of food
preservation recipes and techniques by many state extension services. Keep
up to date!