When I was a child, there was a woman on our block who used to bring my mother small jars of various jams in the summertime. It was good stuff…mostly marmalade as I recall. Yet the thing that made the jars so memorable to me wasn’t what was inside, but what was on top. Under the square of calico cloth that she’d tied around the rim with twine wasn’t a stainless steel lid, but a quarter inch layer of wax, laid directly on top of the surface of the jam. I was fascinated by it, and always fought my twin sister for the privilege of being the first to break the wax layer with a spoon.
That form of canning was commonplace in the first half of the 20th century, and was dying out when I was a kid in the 70’s. Nowadays you hardly see it at all, since it’s considered unsafe. The method works very much the same as the “open kettle” technique I described in my earlier post on the history of canning. Only instead of placing a lid on the jar of simmering jam, the cook would pour a small volume of molten paraffin in. Being lighter than the dense and syrupy jam in the jar, it would float on the top, eventually hardening into a solid layer. Though not as sure-fire as the boiling water canning method, the technique did yield a sanitized product most of the time.
Of course mostly safe aren’t the words you want to hear where edible things are concerned. Yet it’s my belief that the main danger of paraffin canning isn’t the technique itself, but the way contemporary people might use it. Paraffin canning was never intended as a long-term storage solution. Rather it functioned as sort of pre-tupperware, a strategy that would keep a food that isn’t very perishable anyway — namely jam — fresh enough until it could be consumed, usually within a few months time. Indeed the main spoilage issue jam has when it’s left at room temperature is mold or fungus growing in pools of condensed water on its surface (it’s a rare thing — assuming the jam has been made correctly — to find a microbe thriving in the sugary, acidic interior of the jar). Wax sealing was an easy, temporary fix for the problem. The concern now, I think, is that we modern urbanites, who aren’t used to receiving or consuming such goods, would leave wax-sealed jams on our shelves for years.
You can still buy canning wax in many grocery stores. It goes by the name of “household wax” and is usually found in the hardware aisle.