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5 Tips for Canning Tomatoes

Know Your Altitude

A novice canner might underestimate the effect of altitude on the process, but it's not to be taken lightly if you want to do it right. Most of the canning techniques you'll find on the Internet assume that you'll be lower than 1,000 feet above sea level. If you happen to live in Denver, Colo., or any other city above 1,000 feet in altitude, you need to make an adjustment. A good rule of thumb is to add one minute of boiling time for each additional 1,000 feet above sea level.