The trouble with Mason jars lids is that they all appear alike in the package but not all will fit all. When you go to twist the lid onto your jar it doesn’t work because the threading isn’t right. Why? Because there are realy only two standard sizes, one for storing and one for canning. Everything else is meant to trick you into buying more packaging.
Knowing the distinction between wide mouth vs. Regular mouth save money. Time. And jam. Those are the two primary diameters, there’s about 70 millimeters from one side of the jar to another, and about 86 millimeters, as in the chart above. The larger diameter make a difference when filling the jar.
How to Use Mason Jar Lids Correctly
With regular mouth jars (and this is true of almost all), a funnel is necessary for most ingredient. With wide mouth jars, you can simply spoon in big spoonfuls of salsa or throw in whole tomatoes without wrestling with rim of the glass. The wider jars are also more convenient. This is why most home canners switch to wide-mouth jars after a while; they are worth the small extra cost for the lids.
As much as you want to know about your mason jars’ size, you need to understand their anatomy (specifically the lid). All traditional mason jars uses a two-part system. There is ring that screws down over a flat metal disk, which forms the airtight seal. The underside of this flat disk have a very thin coating of sealing compound on it. When heat is applied it becomes pliable and conforms to the jar’s rim, forming a tight seal.
It doesn’t work twice because once the compound is heated then cooled it will no longer stretch back into shape. Reusing this flat lid runs the risk of creating a break in the seal. That’s bad news because you didn’t just waste all that work, you also ruined the contents of the jar.
Then there’s the screw band ring. This is where I’d say that you’ve got another story altogether. Because the actual sealing surface isn’t touched by that piece of metal, the metal ring won’t wear out. As long as they don’t have any dents or rust on them, you can use these things year after year. Toss them if they warp or the threads gets stripped. Keep ’em if not. Again, it’s a little bit, but it’ll save you money in the long run.
A lot of newbies will throw out their used lids and perfectly good rings assuming everything needs to be threw out. Mason jar lids aren’t like other products where brand loyalty comes into play. The whole industry operate by the same standard and all big brands make their lids to match. So, for example, a Ball® or Kerr® lid will fit just fine on a Mason™ jar (provided it’s not a half-gallon we’re talking about!). No need for special lids with special jars. Good thing, right?
If you have a box of vintage bands lying around that you inherited, or stumbled onto a bargain price on a generic cap, no problem. Just confirm the diameter first. As the side-by-side image in the infographic illustrates, the regular size is considerably smaller then the wide mouth; which means there’s a lot more room for the bulkiest ingredients. There is less risk of air pockets forming when packing down heavier items, making it easier to load up.
What is preserved affects the choice of pressure canner vs. The choice depends on the water bath canner, though it is not always determined by the size of the lid. For safety, all foods should have the same style two piece lids whether they be high acid (like jams) or low acid (like meat). Whether it’s a waterbath or a pressure canner, the sealing compound gets softened by the heat.
Do not attempt to actually can using any other kind of special or plastic snap-on lids. They’re meant for storing in the pantry, not for canning and they won’t hold up under pressure. To test that your cans sealed properly, press gently in the middle of the lid when cool. It should flex back. If it pops up and down, throw it back in, or put it right into the fridge. You don’t want pretty jars on your shelf, safe food is the prize.
Once you get the hang of this, it makes an intimidating hardware puzzle into a dependable part of your kitchen routine.