Monday, 28 December 2009

Pop-top jars for jam and preserves (for Americans - 'canning')

Pop-top jars are great and I collect them wherever I find them.  As long as the lids are still in good shape they will reseal time and again.   They make the whole process of making jam and preserves relatively simple and hassle-free.  I do encourage readers to have a go using this method which I found far easier than others.  In this article I explain how the jars can be re-used.  In other articles I share all my recipes.  To find them refer to the index tags at the end of this article.  Once you get the hang of it you'll very likely wonder why you haven't been doing it for years!

This photograph shows a sample of what I've used pop top jars for:
Preserves: nectarines, apricots, apples, pears, black boy peaches and gooseberries.
Jam: plum, apricot and gooseberry; also red currant syrup.

Some years ago when I was first learning about jam and preserves I puzzled at length over what seemed like the complicated business of sterilizing boiling hot jars and fiddling about with various seals and bands.  I did my best but tied myself in knots in the process, got lots of sticky juice over most surfaces in the kitchen, and cracked more than one jar!  I got hot, bothered and rather cross.  I subsequently discovered that none of this was necessary.  Using pop-top jars makes the process easy.

This is an example of what the lids look like.  Note the raised dome in the middle of the lid.  If the dome is sucked down the jar is sealed; if the dome is raised the seal is broken.  If you're still not sure, push the dome down with your finger.  If it moves at all the jar isn't sealed.

I'll write about the process of preparing and cooking fruit and tomatoes elsewhere as the requirements vary from one sort to another.  In this item my focus is on the aspect to do with the jars and getting them to seal.  This process is the same for anything you want to seal in a glass jar.

If opened carefully pop-tops can be re-used many times, so you can gradually build up your own collection for free from any food you happen to buy which has this sort of lid.

If you get serious about it you'll need plenty: think how many pots of jam and tins of fruit you buy a week, then multiply it for the duration of a year and you'll find you'll have plenty of use for a large number!  And if, after all that, you're up to making pickles and relishes as well, you'll need even more!  So far I haven't been quite that energetic.  Even so, I have about 150 which isn't enough.

Most people don't know how to easily open these jars, which is the key to getting a good supply.  And most people who have ever saved them for me wreck the lids in the process - and in any case usually forget they said they would do so after about a week!  Take heart - here is how it can be done - easily.  I've included photographs so you can't be mistaken:
  • Firstly, you need a kitchen implement or any kind of metal tool which has a flat edge about a centimetre long such as you can see on the topmost edge of this tin opener.  Any shorter edge is unlikely to work.

  • You then place that flat edge in the groove between the lid and the adjacent screw-edge of your nice glass jar thus:

    •  ...and rotate it slightly.  This lets just enough air into the jar to relax the seal, and that's it!  No hot water and towels, no banging on the bench, just a little twist and you're done!

    The next requirement for this method is plenty of really hot water and detergent and a fresh kitchen sponge - clean your bench, sink, dish-rack and most of all your jars and lids, really thoroughly. 

    I could not do any of this without a pair of flock-lined rubber kitchen gloves so that I can manage the hot water and handle the jars which get even hotter as the hot liquids are ladled into them.

    Go through the usual process of cooking up whatever it is you are bottling. I have two large stock-pots, one is stainless steel and the other has a non-stick surface; both are easy to use and to clean.

    For cooking and storing food I always use stainless steel and glass where possible. 

    Have the sink filled with really hot water - what you can get from the kitchen tap will probably be hot enough, and lay as many jars as you think you will need in it so that they are fully immersed.

    Place the lids in a heat-proof pot or bowl, and when the fruit is nearly ready, pour boiling water over them.

    At this point, re-fill the sink with the hottest water the tap will produce so that your jars are also really hot.  You don't want them to crack from too great a change of temperature, or to cool the fruit before the lid is on.  If you are preserving fruit as opposed to making jam, have your kettle near the boil so you can top up your jars if you don't have quite enough syrup to reach the very top of the rim. This shouldn't be necessary if you have enough syrup in the pot, which is why it's better to have a little too much syrup than not enough.

    I have a dinner plate next to my pot of boiling fruit and on it a heat-proof bowl partially filled with hot water.  This is so that I can stand my jar in it while I'm ladling fruit into it if I want to, without getting syrup everywhere.
    • When making preserved fruit (which Americans call 'canning') I slightly overfill the jars so that I can be sure that there is no air space in the top of the jar.  When you've filled your jar right to the top, fish a matching lid out of the bowl they are in, quickly flick your gloved finger tip around the rim of the jar to make sure it's clear of pieces of fruit, and carefully screw the lid into place.  If you've overfilled it with syrup as I do, screwing the lid down will force a little excess syrup out.  
    • When filling jars with jam it is not necessary to fill them right to the brim - you can leave a bit of space at the top.
    That's it !!!

    Within five to ten minutes each pop-top will give a loud click as the seal sucks down showing it's successful and you know it's fine.  All you have to do after that is wash the jar and label it.  If you have the occasional jar which doesn't click it means either that the lid is no good, or that it hasn't been screwed into place properly.  Because the sealing becomes evident so quickly, fruit can easily be decanted either back into the pot for re-heating and then re-bottling, or, if you are lucky, simply poured briskly into a waiting very hot jar.  I've got away with that a few times!

    In the five or so years I've been doing this I've had no jars at all go 'off', so the sterilization of the jars as described has been perfectly adequate.  Good luck with yours!

    Later note (22nd Oct 2010): I can see a query on the web about jars that are not actual pop-tops and wondering if these can also be made to seal.  The answer is that if the jar you have has been sealed for supermarket sale you will be able to see a thin rubber seal where the lid fits against the rim of the glass jar.  If the lid has been opened carefully and not wrecked these can be used similarly - it's just that you can't be so sure that they have fully sealed.  The success of the seal can be fairly accurately gauged by the centre having sucked down a little.  I have heaps of these jars and use them for jam if I run out of the others as sealing isn't as crucial as it is for preserves.  As it's turned out I've had no problem with them.  Good luck!

    My method of jam-making can be found in the article:
    My method of making preserves can be found in the article:

    Further instructions for how to make a wide range of jams and preserves can be found via the following link:


    Hannah said...

    Thanks for such a great article! I've just made my first batch of jam today & used pop-top jars :) Here's hoping it works!

    Leigh Christina Russell said...

    Hi Hannah, nice to hear from you. I do hope your pop-tops sealed as expected!

    simone marie said...

    I'm very interested in this as Agee Jars are getting very pricey these days. Do you know if making something like tomato sauce, chutneys, pickles etc that have vinegar in them, do you need to fill right to the brim or leave a gap? And do you ever waterbath the pop top jars?

    Leigh Christina Russell said...

    Hi Simone Marie,
    You should have no problem whatsoever using pop-tops for your yummy sauces and pickles. You don't need to fill them right to the top. A lot of the jars I save and use time and again are from tomato relish, which I've never got around to making myself! If you look at one from the shop you'll see that the manufacturer has left an air gap. I only fill right to the brim if contents is to remain liquid, such as with fruit or bottled tomatoes. I immerse jars in water only to pre-heat before filling, or to wash them clean after they have sealed. Nothing could be simpler. Just make sure you have some nice flock-lined washing-up gloves so you can safely handle those hot jars! Actually I often use little cotton gloves inside ordinary rubber ones.
    Best wishes for your kitchen creations.
    Nice to hear from a Dunedinite, and I hope you are keeping up with your art work!