Why should I buy special preserving jars: can’t I just reuse jars from the supermarket?

We sometimes get asked this question and concerningly, there are numerous sites on social media that actively promote the practice.  This relates to reusing jars such as those you might buy with mayonnaise, tomato pasta sauce or premade sauces.

So to step back from the question, a quick refresher on what a good preserving jar should have:

Tempered glass: this will allow the glass to withstand higher temperatures. 

A secure seal: preserving jars differ in how they achieve this.  Some may have a separate rubber seal or gasket (like Le Parfait or Weck jars) and some have the seal built into the canning lid (like Ball or Familia Wiss jars).

A way to tell if the seal has failed: again, the way different preserving  jars do thi