Weekend Preserver Series: How to Prepare Jars for Canning

Keeping mind that 'every detail must be detailed', let's review preparing jars for canning.

In 1937 the Farm Security Administration (FSA) was charged with working on the complex problem of farming and rural poverty. Self-sufficiency thus home food preservation were a part of the program. Library of Congress, Prints and Photography Division, FSA/OWI Collection, #LC-USF346- 051630-D.

Washing and Inspecting Jars

  • Wash and rinse jars. Yes, I know this is a given. The jars can be inspected for nicks, cracks, and deep scratches at the same time. New cases of jars need to be washed! Why? New jars have the residue of the lubricant used to ensure the jars can be removed from the molds during manufacturing.
  • Don't use metal scrubbers or anything metal to clean canning jars. Even some course scouring powders can be problematic. Scratches can become cracks which isn't a good thing. Use care or don't use metal utensils when scooping food out of jars! Wooden utensils are very handy to use to protect canning jars.
  • Remove mineral deposits by soaking jars in 1 gallon of water and 1 cup of vinegar.
  • Inspect jars. It is much easier to check for chips or cracks on the jar rims and cracks in the body of the jar before it's time to fill the jars. Check for any stuck on food that can hide in the threads of the jar or in the bottom. 

Sterilizing Jars

Jars must be sterilized if the processing time is less than 10 minutes. That said, I know that some folks like to sterilize jars just for good measure regardless of processing time or processing method (boiling bath, pressure, or steam).

When I get jars from friends or buy them used, I inspect, wash, sterilize, and store. It's kinda silly to wash and sterilize the jars but I've found it makes it easier when I am getting ready for a canning session. All the jars I have stored are ready to prepare to can rather than ready to be soaked to remove deposits or old food. I then wash again when it is time to can.

Both water and heat are required for sterilization: Place jars in a pot of water. The jars must be covered with water. Boil for 10 minutes. 

Prepare Extra Jars

  • Prepare an extra jar or two for each canning session. Often you won't need it but it is nice to be ready when the jars need to be filled and you discover that one is cracked or nicked or the yield is more than you anticipated.
  • Keep notes regarding your yields so you know how many jars to prepare for the same recipe next time. 
  • It can be helpful to prepare a smaller jar when you are working with fruit preserves--if you are canning 1/2 pint jars, prepare a 1/4 pint jar for that last bit of preserves and in most instances it should be processed in a water bath canner for the same amount of time as the 1/2 pint (we're talking about the aforementioned example of fruit preserves). Yes, it's nice to have that extra bit of jam in the fridge but if you are in the height of canning season that extra bit of jam will morph into ten 1/4 pint jars. Plus, 1/4 pint jars make terrific gifts--a medley of cute little jars of jam! Winner!

Keeping Jars Hot during Canning Session

  • Use a stock pot with simmering hot water. 
  • Use the canner with simmering hot water.
  • Heat oven to 325 degrees and use a roasting pan with water in the bottom. Invert canning jars in the water.
  • Use a dishwasher. A closed, hot dishwasher will do the trick too. Though, I have zero experience with this method.

Storing Empty Jars

Every seasoned canner has a time honed storage method. Here are a few things that you might want to consider:

  • Easy access. It really isn't fun to need to dig out jars from a difficult location. 
  • Organized by jar size and type. Every time I put jars away I put the jars away by size. I also make sure that I keep my vintage and special jars separated to make it easy when I am looking for them.
  • Label boxes or bins. 
  • Storing in transparent plastic bins. I haven't justified buying enough plastic bins for all my canning jars but the bins do protect the jars from dust and so forth. Be sure that how you store the jars protects the rims from nicks.

Be safe and eat well.


Reliable Resources

Please be aware of acceptable modifications (University of Wisconsin-Madison Extension PDF, May 2015) that can be made to a home canning recipe--keep in mind that not all modifications, even popular ones are safe! 

If you are ever in doubt regarding safety, be sure to check a reliable resource. Even recently published books might contain recipes that are not suitable for safe home canning