Canning jars should ideally be sealed using a pressure canner or hot water bath technique to remove air and create a vacuum seal. However, boiling is time-consuming and adds several steps to the canning process. This may leave you wishing there were alternative methods to seal canning jars that do not involve boiling.
Canning jars can be sealed without boiling using open kettle canning or sealing the jars using paraffin wax. These methods are only viable for preserving food for short periods that should not exceed a few months. The oven canning technique is dangerous and should not be used.
Sealing jars without boiling them is common practice in many parts of the world. If canned food reaches a high heat and a vacuum is created inside the jar, the contents will last longer. Let’s explore some alternative methods to seal canning jars without boiling water.
How To Seal Canning Jars Without Boiling
There is no substitute for a pressure canner when canning low-acid food, including meat, vegetables, and seafood. The methods described here are only alternatives for selected recipes that would typically be sealed using a water bath canner, for example, pickles, preserves, and salsa.
The aim during canning is to kill bacteria and eliminate air around the food and create an airtight environment inside the jars. Sealing jars tightly during the canning process is imperative to prevent food from spoiling and extend its shelf life.
Canning without boiling should never become standard practice for anyone wanting to preserve food safely for extended periods. If you don’t have a hot water bath canner, creating a makeshift one using a large stock pot is simple. That way, you can always store and serve your canned products confidently.
Although there are several ways to seal canning jars without boiling, they all have in common that the jars and lids must be completely clean. Contents must be piping hot when decanted into the jars, and lids should never be reused. It is an excellent idea to boil jars to sterilize them before use.
Open Kettle Canning
If you travel to Europe or even to Amish country, you are likely to come across open kettle canning, also called upside-down canning. If done correctly, open kettle canning can result in a firm vacuum seal.
Upside-down canning is the standard method used by so-called rebel canners; however, it is not considered safe by the USDA. Unlike hot water bath canning, where contents are superheated inside the jar, and a tight vacuum is formed, there is room for error. Always listen carefully for the distinctive ‘pop’ sound indicating that the lid is tightly sealed.
To use the upside-down canning method, take note of the following:
- It only works with ingredients that contain a lot of liquid. There should be no gaps against the lid when the jar is flipped upside down.
- The contents decanted into the jar must be extremely hot for open kettle canning to be effective. The vacuum is created due to the hot contents superheating the metal lid.
- Just because the lid makes a popping sound and you get a seal does not mean the contents are safe. If the food was not hot enough, or the jars weren’t sterile, bacteria would simply be locked into the sealed jars.
Use the following method to upside-down seal canning jars:
- Prepare the mixture you want to can and carefully decant it into the sterilized, heated jars while it is very hot.
- Leave a headspace of around 1 – 1.5 inches.
- Wipe the rim to ensure that it is clean.
- Place a flat lid on top and tighten the band enough to prevent spillage.
- As soon as the lid is secured with the band, flip the jar and leave it upside-down. You will notice the contents drop directly onto the jar’s lid.
- Leave the jars in this position for around 15 minutes.
- Now turn the jars right side up. Wear oven gloves, as the jars may still be too hot to grip.
If your upside-down canning technique was successful, you should hear the lids pop a few minutes after being placed upright. Let the jars cool down completely before moving them to your pantry.
If a tight vacuum seal was not formed, the food should be reboiled and canned again. Alternatively, jars can be stored in the refrigerator and used as soon as possible.
Paraffin Wax Method
The paraffin wax method is considered outdated for sealing jars, but it can work well if you don’t plan to store your jars too long. Food preserved in jars using a paraffin wax seal should be consumed within a few months.
Many people fondly remember removing the solid wax plug at the top of bottles at their grandma’s house. While this method is considered outdated and no longer endorsed, it can prolong the shelf life of preserved items longer than without this treatment.
To use the paraffin wax method to seal your jars, you will need the following:
- Sterile canning jars with new lids
- Enough food-grade paraffin wax to create a solid layer at the top of each jar.
- A double boiler – A DIY double boiler can be made using two different-sized pots, one inside the other.
- Melt the paraffin wax in the double boiler. This must be done slowly, as the wax can get extremely hot and even ignite.
- Fill your canning jars with your hot food leaving between a half inch to an inch of headspace in each jar.
- Carefully spoon the hot wax into the headspace in the jars. It will have a watery appearance while it is hot.
- Fill the jar with wax until it is level with the rim. The wax may start looking opaque as it begins to cool.
- Before it cools completely, quickly place the lids on top of the wax and seal it tightly.
As the jars cool, the wax will revert to a solid form that forms the wax plug over the food. Sealing jars using paraffin wax is only recommended for short-term use.
Sealing Jars Using A Vacuum Sealer
Vacuum sealing is an excellent method to remove air from jars when storing dry food in mason jars. It is not recommended for wet-pack canning and should only be used if you plan to refrigerate your vacuum-sealed jars.
Is Oven Canning Safe?
Oven canning is never safe. This method which continues to be used by some home canners is extremely risky. In addition to not adequately heating the contents of the jars to the required temperatures, there is a significant danger that the jars could explode in the dry heat inside an oven.
It may sound tempting to be able to seal jars for storage in a hot oven, but there are plenty of good reasons why this method should be avoided:
- Mason jars are not tempered for oven use. They were created for canning using water-based techniques. The dry heat inside an oven could cause the glass jars to explode.
- The temperature of the food in the jar and the inside of the oven will not be the same. Since the outside of the jar will be bombarded by dry heat while the interior will be holding wet packed food, there is no guarantee that the food will reach the required temperature to kill microorganisms.
- No safe processing times for oven canning have been established. It is, therefore, impossible to know how long the jars must stay in the oven to be safely sealed.
Can Food Be Recanned If The Lid Does Not Seal?
Canned food can be recanned if the unsealed jar is noticed within 24 hours. Try to discover why the lid did not seal. Check the jar rim for any irregularities, and if necessary, use another jar.
Transfer the contents of the unsealed jar to a new jar and use a new lid. Then process the jar using a hot water bath or pressure canner to seal it. If a seal is still not obtained, store the food in the refrigerator and use it as soon as possible.
Do You Have To Boil Jars To Seal Them?
Hygiene is essential when canning, and it is good practice to thoroughly wash all jars, lids, and equipment at the start of the process. Boiling empty jars for at least ten minutes is commonly undertaken to sterilize them before being filled.
If the food is being processed for longer than 10 minutes in a hot water bath or a pressure canner, it is not necessary to go overboard sterilizing jars. All the microorganisms that may be lurking on them will be destroyed during these intensive procedures.
Canning jars that will not be processed using a water bath or pressure canner must be boiled to sterilize before filling. This also applies to preserved food processed in a water bath for less than ten minutes.
Methods commonly used to seal jars without boiling include open kettle canning and paraffin wax sealing. Both of these should only be used to preserve food for short periods. Oven canning should never be considered as it is not safe.
While it is possible to seal canning jars without boiling, it is not recommended. Skipping this essential heat treatment process may save time, but it can lead to uncertainty about the long-term safety of your food.