Last Updated on December 31, 2022 by Shari Mason
Canning jars is one of the most effective processes to preserve food and extend its shelf life up to years. In this method, food-filled jars or containers must be submerged in boiling water bath canning to kill microorganisms and vacuum-sealed the jars with no air bubbles.
But one question is still popping up – do jars have to be fully submerged when canning? To know the answer, keep scrolling and find out.
Should You Fully Submerge Jars When Canning?
Yes, every canning jar has to be fully submerged in a boiling water bath canner during canning. It prevents the air from returning to the jars after escaping the pressure canner during boiling temperatures.
You can also use a wooden spatula to remove trapped air bubbles inside the glass jar. A water bath canner shouldn’t have too much headspace, and the jars should be fully submerged when canning in the boiling water.
All the jars in the pressure canner must be sealed correctly and should be free from air bubbles to achieve a successful vacuum seal of canning jars.
How Deep Should It Be Submerged?
To completely submerge the glass jars in the boiling water bath canner, your canning pot should be four inches taller than the glass jars. You can use a canning wire rack inside the stock pot for additional space between jars.
The hot water should cover jars about an inch above the lids and another one to two inches from the boiling water bath.
Before starting your water bath canning projects, you must sterilize jars upside the canning pot. The recipe calls the processing time of pressure canning.
High-acid foods are ideal in canning water baths because it fights botulinum pathogens during the canning process of jars. 
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Tips & Tricks When Fully Submerging Jars in Canning
Invest in Jar Rack
If you’re a beginner in the water bath canning method, you should invest in a heavy-duty jar rack. It is one of the most valuable pressure canning materials because it protects the jars from the direct heat of the pot’s bottom during the canning process.
The jar rack helps reduces heat absorption of the glass jars, making them more durable during the boiling process. It is also ideal if you’re canning multiple jars in a large pot.
Ensure Proper Headspace
During water bath canning, you should ensure that there is always enough headspace between the submerged jars and boiling water. Canning jars should be upside with the boiling water bath covering the lids about two inches.
You should never add water to a rolling boil because it will change the proper temperature of the water bath, might break jars, or cause the canning process to fail.
Start in Small Jars and Quantities
Start in small quantities of smaller jars, like one to two jars, if you’re new to the home canning food method. Canning jars to preserve food is a complex process of preserving food in jars and needs more practice to achieve successful vacuum seal jars.
When you have mastered the processing times of water bath canning, you may upgrade to a large pot pressure canner and mason jars.
Can the Jars Break When Canning?
Jars could break during canning in boiling water if the jars you used are not canning jars or glass jars made for canning. Jars could also break in too much heat if you put them on the bottom of the pot instead of the jars stand.
Jars could break too in thermal shock, so avoid sudden changes in temperature like adding cold water to a rolling boil, putting hot jars in cold water, or soaking cold jars in bath water. Old canning jars could also break in boiling water, so avoid using them. 
What To Do When The Jars Float When Canning?
Sealed jars float when canning due to some reasons. Ensure that you fill your mason jars with acidic foods so they’re not lightweight when the water bath is above their lids.
Floating jars are also caused by too much headspace, so ensure your water level matches the recipe. Jars submerged might float too because of too much boiling water; always take note of the processing time when canning.
The low hot water bath level in too much boiling is a helpful hint for removing jars on time. Some recipes require a short boiling water process only.
Can you lay jars down when canning?
No, you can’t lay jars in the pressure canner when canning because the rising water temperature from the bottom will weaken the seal of the filled jars. Upside jars during water bathing provide adequate boiling water flow on all jars.
Not following the processing time of the water bathing method is not advisable because it may lead to unsuccessful canning results.
How long do you boil jars for canning?
Usually, the processing time for canning jars is twenty to twenty-five minutes. It also depends on the canning jar content. Too much boiling might cause the jars to float, so monitoring the whole canning process is essential.
Is it OK to reuse canning water?
Yes, you can reuse the canning water bath unless it is already dirty or has become oily. Some people reuse their canning water, but they ensure that all canning materials are washed and sterilized before using them again.
Can I use plastic jars for canning?
Yes, you can use plastic jars for water bathing as long as it is specially made for canning and are food-grade plastic jars.
Plastic jars are microwaveable and can withstand high heat and even high boiling temperatures in a water bath. But if you’re water-bathing solid foods, it is better to use glass jars.
Generally, sterilized jars should be fully submerged when canning in a home food preservation process with the proper headspace according to the recipe.
Acidic foods are ideal for home canning, but in modern recipes, pressure canning or steam canning are used for low-acid foods in a short boiling water process.
Whichever process you use, jars should be completely submerged in pressure canners when canning. Let the jars cool in warm water before moving to avoid vacuum failure.
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