RE: Jam (preserves)
My Mum used to preserve her fruit jams in regular sterilised recycled screw-top jars and did exactly as you describe with the paraffin wax on top. As long as the jars are sterilised properly it shouldn’t be an issue for items with high sugar content.
You may want to google to check the amount of time you should (or shouldn’t!) leave between filling and adding the parafin wax though as I would have thought the sooner the better after cooling to get the seal on to avoid contamination. I have read that there is now some evidence to suggest that paraffin may not give a perfect seal and the powers that be don’t recommend it anymore…but then it did okay for our mothers and grandmothers!
In later years when they became available Mum would use a a product called “JamSeal” or now called “Kleerview” from Australia’s best known preserving company Fowlers Vacola. They are really great and simple to use - each sheet is very thin plastic (like cellophane) square which you place on top of the jar after filling with hot jam and pop a rubber band around the top. As the contents cool and settle, the square sticks shrinks and forms an airtight seal. They cost about AU $2.50 per pack of 24 including 24 rubber bands and jar labels, you can get them on ebay or http://www.bakeandbrew.com.au are very helpful and will probably ship direct to you. Personally if you can source them I think they are a less messy option than the wax!
RE: Preserved fruit:
If you intend to cook then pack and can (jar) the peaches and plums in the hot cooking liquid it shouldn’t be an issue to use the re-cycled jars either but I wouldn’t use these if you intend doing the cold pack and cook in jar method of preserving.
Hope this helps! Enjoy that wonderful harvest!
P.S.My neighbour makes all his delicious strawberry and apricot jams with pre-loved jam jars too - he just buys some plastic screwtop lids from the local hardware store to fit.
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