Sealing Preserves
I read so much mixed messaging about sealing preserves that imbue the cap/lid/seal with almost magical powers I thought that it would be a good idea to set some things straight.
In the days when we had boulders for furniture and the woolly mammoth roamed the land there were no lids, or jars come to that, but people still preserved their food. I grant you that they didn't start making jam, or their sweet paste version of it until some bright spark invented a cooking pot but they still preserved their food. Sugar is documented as existing over 11,000 years ago and was used extensively. The early people learned quite quickly in terms of an evolutionary timeline, that removing moisture from food was the key to keeping their food edible for longer than just leaving it lying around for a marauder to eat, and the more moisture they removed, the longer it kept.
Using a lid didn't once cross their mind. What's a lid?
Roll forward to 500-600 years ago when not a great deal had changed, they were still making a sweet paste from the wild fruits available which were mainly quince and wild berries, and honey or sugar. There were no fruits as we know them yet. These were cooked slowly to a stiff paste, poured onto wooden plates or trenchers. Once cold the discs of 'jam' were peeled off the plate and stacked in piles with fresh herbs layered in between to discourage flies and vermin. Kept in a cool store a disc was brought to the dinner table and slices taken as required. This is the origin of us using sweet sauces such as redcurrant jelly with lamb to this day.
Since then we have gone through pottery jars and covers, glass jars which were covered with a variety of vellum ( animal skin ), clean-ish paper, poured wax, oiled paper, cellophane and wax discs and finally - LIDS! All of these mechanics do one job - they keep out dust, flies, wasps, fingers (!) and to a greater or lesser degree - moisture. We work hard to extract moisture in the making of the preserve, sweet or savoury, and we need to keep it that way. All moulds, yeasts and bacteria need a certain level of moisture to thrive which explains why we had mouldy jam when we were growing up in the 60s and 70s. We only had waxed discs and cellophane - which is porous - so in our damp old, non-centrally heated homes moisture was able to cross the barrier and mould was inevitable.
Modern Lids
This scenario is not necessary today. We are fortunate that we can buy new lids to use on our preserves, whatever we are making. Please, please do not give these small pieces of tinplate magical powers.
Just because a jar is 'sealed' it does not make the contents of the jar safe.
The button on the store bought jar that you are reusing should not give you a sense of false security - it is not there to guarantee the home-made contents that you have changed the recipe of or made up from scratch on the basis of some shakey 'knowledge' of someone you don't know, that you have read on-line.
The button lid was devised by commercial manufacturers who do not make preserves in the same way. Sometimes the jars are filled with a cold product into a cold jar - they are then vaccum sealed and the button indicates that the jar is sealed tight and the jar can go forward from the production line on its considerable jolting journey until it will rest on the store shelf. When you choose the product you can be confident in its manufacturing integrity - and you can also be sure that nobody has opened the jar and contaminated it in any way (!)
When you use a button lid at home - especially if you re-use a lid - the button may or may not depress. This doesn't necessarily mean theat the contents are safe or unsafe. It just means the button hasn't depressed and unless you are vacuum sealing with a piece of kit it doesn't really signify anything about the contents. Whenever possible jars of preserves should be hot filled. Fill the jars right to the top and put on the lids. Put them to one side to cool for 24 hours - resist the urge to tip them from side to side or turn them upside down. When cold you will see that the jam/chutney has shrunk back and a gap appears. This gap is a vacuum which draws the lid down tight onto the rim of the jar and nothing undesirable can grow in that environment. You can be confident that the jar has sealed - but as long as you have made the preserve correctly it will be safe to eat whether the jar has 'sealed' or not - remember the plates? And - properly made preserves do not need to be refrigerated unless the label/recipe says so.
If you are making a cold preserve - pickled onions for example - the modern lug lid will not seal. The sealing compond on the underside of the lid is activated by heat only and if you try to tighten the lid by repeatedly screwing it round, the shaped lugs on the jar rim will deform the metal lug shapes on the lid and it will then be useless. Cold-filled jars will leak if transported so if you need them sealed you will need to consider water bathing if this is appropriate for your preserve.
This is why it is so important not to mess about with recipes until you fully understand how the food is being preserved, what are the important factors in that preservation method, have you just ditched the key part of the process? Why? What is so inconvenient about the process that you need to change things that have been proven thoroughly over hundreds ar even thousands of years?
If you are uncertain why things have/have not turned out as expected I can confidently say immediately that it is not down to the jar or lid - it is always process. If you have questions I have the answers for you and a very good place to start is in The Library of my School. Preserving for Beginners is packed with the answers to the questions that you have and you can watch it for free. You can even cook along with me and make some jam, maybe your first jam - and what a good way to begin, the right way. Here's the thing though, (whispers ) you have to actually watch the video - you can't absorb it just by reading the title. A little bit of effort now will set you on the right path but don't believe that is the end of the instruction. I have been studying this subject for the whole of my life since I was 5 years old and I learn something every day.
I am here in any way that you want to contact me and I am ready and willing to help yopu be successful.