The four families of jars
Rubber-seal jars with a wire clamp
The classic French jar: a glass lid attached by a metal clamp, and a rubber ring that seals as it cools. To open it, pull the tab of the ring. The ring is designed for a single use; the jar itself lasts for decades.
Glass-lid jars with clips
A loose glass lid, a rubber ring and two steel clips that hold the lid during processing and are removed once the jar has cooled. If the ring's tab points downwards, the jar is sealed. Rings that stay supple and intact can be reused; when in doubt, replace them.
Twist-off jars
A metal screw lid with a sealing compound inside, like on store-bought jam jars. Practical and cheap, but the lid is designed for a single use: a reused lid seals less reliably. The jar is sealed when the centre of the lid is hollow and does not click.
Mason jars
The North American standard: a flat lid with a sealing compound, held by a screw band. The flat lid is single use, the band is reusable. Remove the band once the jar has cooled, so that a lid that comes loose during storage does not go unnoticed.
Which size for what?
| Size | Best for |
|---|---|
| 125 to 250 ml | Jams, jellies, chutneys, jars to give away |
| 350 to 500 ml | Sauces, compotes, a vegetable side dish for one or two |
| 750 ml to 1 litre | Vegetables, soups, cooked dishes for the family |
| 1.5 litres and more | Fruits in syrup, large families, lacto-fermentation |
Processing times always depend on the size of the jar: a recipe tested for 500 ml jars needs more time in 1 litre jars. Better to have several small jars than one large jar opened and left in the fridge.
What can be reused?
- The glass: yes, indefinitely, as long as the rim has no chip and the jar no crack.
- Rubber rings for clamp jars and twist-off or Mason lids: no, use new ones for each batch.
- Clamps, clips and screw bands: yes, as long as they are not rusty or bent.
Second-hand jars are a good deal: check each rim with your finger and buy new rings of the right diameter — measure the opening, sizes vary from one model to another.
Practical tips
- Straight-sided, wide-mouth jars are easier to fill, to empty and to clean.
- Choose a few standard sizes: your seals, lids and shelves will thank you.
- Keep a stock of spare rings and lids before the season starts — they run out in summer.
