Plastic caps from many standard Mayo-style jars will fit regular-mouth (70 mm) Mason jars for refrigerated and dry storage.
To be clear, this usage covers refrigerated storage of opened home canned goods, and dry storage of dry goods — NOT canning use.
Notice in the photo below that even commercially, these lids aren’t used to maintain a shelf-stable sterile seal. A paper and metal “lid” does that after the “canning” process in the factory. The plastic caps are just provided to the consumer as a convenience for storing the opened bottle in the the fridge.
What jars do they work with
The standard mayo-jar plastic caps will work with standard-mouth (70 mm) Mason jars, regardless of the brand of the jar, or the volume capacity of the jar.
Depending on where you are, and what products and brands you buy, you may see these lids in white, green, yellow, blue or red.
Different colours could be used to colour-code things in the fridge or cupboards, say, for university room-mates sharing a kitchen, or if you wanted to colour code different things for household storage.
Here they are below on Ball, Bernardin, Kerr, and Golden Harvest regular mouth (70 mm) jars.
These storage lids would also work on regular mouth (70 mm) jars from other jar manufacturers such as Kilner Rayware, some Frutta del Prato jars, and some Quatro Staggioni jars.
Shown below are the equivalent white Mason jar storage caps that you can buy separately from Ball and Bernardin.
You may say, you’d rather buy the “real things” because they will last longer.
Sadly, that’s not the case. Whereas a plastic storage cap that comes with a mayo or peanut butter jar seems to last forever in usage (depending on how long you want to admit keeping that jar of mayo in the fridge!), the photo below shows the Jarden storage caps, marketed under the names of Ball and Berardin, after just a few months of use.
The purchased ones may not prove long-lasting for some people.
Miscellaneous points to consider
- For wide-mouth (85 mm) jars, we haven’t yet found a commercial product plastic storage cap that can be used. If you find a store product that comes with one, let us know;
- Do Kraft, Heinz, various generic brands endorse this upcycling re-use of their Mayo-jar plastic caps? Of course not — there’s no upside for them to do so. They clearly have confidence in the caps’ ability to function for shelf storage, as they are sold from shelves in stores, and in the caps’ fitness for refrigerated storage, as that is what why they are supplied for when the seal is broken;
- These mayo caps appear to survive repeated trips in the dishwasher just fine;
- They appear to stand up to at least four or more “recycled lifetimes”;
- Just as you would when using them with Mayo jars etc, don’t heat or put in microwave etc;
- We don’t have any experience to relate on using them in the freezer;
- Some, such as the red ones in those photos, have just slightly shorter “collars” on them, but still work just fine;
- Not all necessarily fit — you may have to try various ones until you discover which ones in your region to start “collecting” instead of tossing out.