The Fowler’s Vacola preserving system uses glass jars, rubber ring seals and pressed metal lids, much like American Mason jars (also known as Ball jars), except that the jars and lids are not threaded. During the canning process, while still hot, the lids are secured by metal tension clips which are removed once cooled and a vacuum seal has formed, which keeps the lid firmly in place.
The jars themselves are very robust and if you buy the stainless steel versions of the lids they will last you a lifetime. In place of the Fowlers jars you can also use Mason Jars and any jar with an undamaged metal lid.
For information on the latest Fowlers Preserving units see: Fowlers Electric Preserving Unit
Fruit (such as apples, pears, apricots, peaches) can be preserved as it has a high sugar content, though usually with a little sugar added for flavour purposes. Tomatoes can also be preserved as they are high in acid. Vegetables cannot be preserved unless infused with a vinegar mixture.
Meat, fish, chicken or dairy products cannot be preserved using the Fowlers system due to the risk of botulism! For these food stuffs you need temperatures higher than boiling point, which can only be achieved with a canning pressure cooker.
If using the Fowlers preserving method make sure you read the instruction booklet that comes with each unit carefully to make sure you are preserving the right types of food in the proper manner.
FOWLERS JARS LEFT TO RIGHT: No 14 (350 ml), No 20 (600 ml), No 27 (800 ml) jars and No 31 (1 litre) jars. The number 27 jar is no longer sold but still can be readily bought second hand. It its tall narrow shape makes it a little awkward to fully but is useful when used in combination with the larger No 31 jars to make the best use of space.
In theory the rubber rings are supposed to be single use only, but I have found that they can usually be used several times before they become unusable.
LEFT: Two sizes of Mason/Ball jars and a lid. RIGHT: Assorted metal lidded jars with jam in them. I routinely process my jams using the Fowlers system as it eliminates the risk of them going mouldy.