All About Canning Lids: The Anatomy and Common Problems

Canning Lids
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Canning Lids

Canning is serious business. There are actually established scientific and safety guidelines in place to guide home canners on all the proper procedures and techniques of canning. Learning how to can is an excellent step towards self-sufficiency.

However, if not done correctly, not only will your hard work be wasted as the food will not be able to keep, but it could also result in Clostridium botulinum bacteria, which is responsible for botulism. The repercussions of botulism can be debilitating and can result in a host of health issues that can be avoided easily by following canning safety guidelines.

All About Canning Lids

One of the most important components of canning is the canning lids. A tightly sealed lid is vital for canning to occur successfully. Without canning lids, the sealing process would not occur, which would render the entire canning process useless. Canning lids are paramount for preserving freshness as well as guaranteeing a vacuum seal.

The anatomy of a canning lid

Canning lids come in 2 varieties, namely the plastic and metal coated variety. Metal coated lids are designed for one-time use only. You should only use metal coated lids that have been USDA recommended and approved. You also want to pick metal coated canning lids that are both BPA-free and phthalate-free.

BPA and phthalates should be avoided because they cause lids to buckle easily and are responsible for common seal failures. Metal coated lids should never be re-used for the purposes of food canning because once the lid is used, the seal consequently compresses, which makes it harder to trap air on the second re-use.

Plastic lids, on the other hand, can be a great alternative to metal canning lids. Most plastic canning lids are available in 2 parts- the rubber ring and the plastic disk. Plastic lids can be reused over and over for both pressure canning and water baths. Plastic lids are also usually BPA free but since they are re-usable, they require extra caution when reusing.

As canning has continued to become more popular, more and more caning lids brands are released into the market. You should never use a canning lid that has not been tested and tried. You should also do your best to avoid using canning lids that have rusts and dents as they can prevent the airtight seal needed to keep food safe from occurring.

Sometimes jar lids also come pre-treated with paraffin. If you are using these types of canning lids, you should only use them once as the heat from canning deforms the paraffin layer in order for a seal to be created. As such, once a paraffin treated canning lid is used, it can never be effectively used for canning again.

Tightening canning lids

When it comes to tightening your canning lids, you should ensure not to tighten the lids too tightly. Canning lids should only be finger tightened; if they are too tight, they will not be able to let out air properly. If this takes place, the seal will be compromised and it should be an indication that the canning process has failed.

Most two-piece canning lids produce a pop sound when they are cooling. The pop sound is usually a sign that the sealing process has been completed. It is produced as the lid becomes sucked down by the vacuum created by the cooling and contracting food that is contained inside the jar.

There are several ways to test whether a jar has sealed completely. After cooling for some time, consider using one of the following techniques to test whether sealing has occurred:

  • The middle of the lid should be pressed with a finger. If the lid pops or springs up when the finger is released, it should be an indication that the lid is still unsealed.
  • When the jar of food is held at eye level, the lid should have a concave shape. If the center of the jar is flat or bulging, it should be a sign that sealing has not occurred.

Why your lids are not tightening

You are using the wrong jars or lids

Lids are of particular importance to the canning process because they make or break the process. When canning, you should only use jars that have been approved for food canning. Using any other type will certainly not produce the seal needed to keep food preserved and safe to eat.

While canning jars and rings can be re-used severally if they are still in great condition, canning lids and the rubber seal compound that forms the seal are only designed for one-time use. As such, if you have a lid that looks like it has been used before, it is best to use it for other purposes such as storage and freezing.

Your rings have issues

If you have jars and lids that are in excellent condition, the last thing that you want to do is ruin all your hard work by using defective rings. Using rings that have rusted or do not fit properly can prevent your lids from sealing. If you are also using bent rings, they will not apply sufficient pressure around the lid to create a seal. Before you use any rings, try testing them by screwing them on a jar beforehand. Run your fingers across the edge to check if there are any bumps or presence of rust.

A dirty jar rim

For you to get a proper seal, your jar rims must be clean. This means that there should not be any traces of food, grease, spillage or any other type of residue that will stand between the lid and a tight seal. Even the slightest amount of dirt can cause an issue. Therefore, ensure that you have wiped your rims clean before trying to seal your food contents.

Using loose bands

If your band is not screwed tightly enough, the sealing process will be compromised. Most manufacturers recommend tightening your bands until you reach the point of resistance. If the band is too loose, the lid will not settle onto the jar rim properly. If it is too tight, the venting process will not take place as it should which will obviously prevent a vacuum from being created as the jar continues to cool.

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