A quick refresher
For the newbies in the crowd, plastisol closures are metal lids lined with PVC along the perimeter. These closures can be matched with glass jars to create a tamper-evident, vacuum seal. The process occurs as the solid plastisol material is melted (through heat transference from the product in the glass jar, no lid pre-heating necessary) and eventually cools along the landing of the glass jar, in turn creating the vacuum seal.
Real world application
Meet Canning Carl. He’s ready to make some of his world famous (at least that’s what his mom says) strawberry jam. Previous canning posts explain the two canning methods, boiling water canning (recommended processing for high-acid food) and pressure canning (recommended processing for low-acid food). Strawberries and most other fruit are high-acid products. This means Carl should process his jam via the boiling water method. Though this isn’t his first canning rodeo, he’s never matched his glass jars with plastisol closures before. Where should he start? We’ll catch up with Carl later.
To boiling water bath, or not to boiling water bath?
An extensive discussion took place in the comments of our previous post on plastisol regarding the exact use of these lids. We know they’re meant to form a seal with glass jars, but under what conditions? Are plastisol closures designed to be used in both boiling water canning and pressure canning processes? Maybe it’s an either or situation, or maybe they aren’t suitable for any type of processing. Whatever the definitive answer is, it’s about time we get to the bottom of this issue.
An expert opinion
You don’t have to be a thermodynamics physicist to consider the basics. A boiling water canner maintains temperatures capable of boiling water, or in other words, 212 ° F. Pressure canners maintain a much higher heat level. The question is whether or not plastisol closures are capable of functioning under these extreme temperatures.
For lack of a better answer, some are and some aren’t. Continuous thread plastisol lids have a lower heat tolerance than other plastisols and should only be used in hot fill cases, where processing is not part of the equation. Lug/Twist plastisol lids on the other hand are fully capable of enduring boiling water temperatures up to 220° F. Any processing over this temperature, mainly pressure canning, requires a different, high heat (formerly known as a retort) liner for effective use. We don't stock high heat lined closures but if that's what you're after give us a call and we'll be happy to help you out.
The verdict The final judgment has been revealed! Glass jars and plastisol closures can take the heat! In levels, that is.
1. Continuous thread closures: hot fill
2. Lug/Twist caps: boiling water bath
3. High heat liners: pressure canning
Summing it all up…
It feels good to have a resolution, doesn’t it? Canning Carl can proceed with his strawberry jam (using a Lug/Twist cap) and we all know exactly which plastisol lid-glass jar combo we need to maximize our food preserving experiences.
Still loving plastisol? Please share your experiences using plastisol closures or submit any other questions you have in the comments!
I will be putting hot relish in the jars no hot water bath will this lid seal my relish
ReplyDeleteHi Anonymous,
ReplyDeleteIn most cases, as long as you are packaging the relish in a glass container a plastisol lid will seal it, but make sure you get the right kind of plastisol lid.
We recommend using continuous thread plastisol closures on hot fill projects (using hot product, no hot water bath processing), that's the kind of lid you need.
Feel free to give us a call at 1-800-473-4144 if you have any other questions or would like assistance in finding the right lid. Good luck with your relish!
I am going to preserve strawberry jam. Is the hot water bath time the same as the two piece can? I am doing 4 oz. jars with the one piece plastisol lid.
ReplyDeleteHi Anonymous,
ReplyDeleteThanks for your question. Yes, the processing time should be the same, whether you're using a two-piece canning closure or a plastisol lid. Please make sure that you are using a lug/twist finish plastisol lid, a continuous thread lid will not seal properly in a hot water bath. Thanks again for posting and let us know if you have any other questions!
HI there: appreciate your interest in sorting out the plastisol debate for canners. I was surprised at your recommendation of lug closures for the hot water bath. If one uses the traditional ring and lid style closure (or a continuous thread cap) in a hot water bath, you only tighten the ring (cap) to 'finger tip' tight so as to allow hot air to escape and thus create a vacuum when the jar and lid cool. After it cools then you tighten the cap fully. How does a lug lid allow air to escape during the hot water bath? I question it because a lug lid once placed on the jar is snug.
ReplyDeletethank you!
Hi Anonymous,
ReplyDeleteThanks for your question. First off, though we do recommend the use of lug plastisol closures for hot bath processes, we do not discourage the use of the typical, two-piece canning lids you mention in your post.
We suggest only using lug plastisol closures for hot bath purposes because the the plastisol used on continuous thread closures cannot tolerate the high temperature involved in hot bath canning.
According to the USDA's Complete Guide to Home Canning, canners should never retighten lids after processing jars. Any type of closure should be firmly (not too loose, but not too tight)applied to jars before they undergo processing (air bubbles can be removed with a spatula before sealing the lid). After processing our lug plastisol closures will seal, just like two-piece lids do, while cooling.
Does this answer your question? Be sure to write back if you have any others. Thanks again for commenting.