How long do you soak Mason jar lids?
Lids should not be sterilized but some say they must be hot: Submerge them in simmering water for 10 minutes (but feel free to skip this step if you're following the updated guidelines from Ball® Brand).
Just before filling them, invert jars onto a kitchen towel to dry. (Jars should be filled while still hot.) Sterilize lids in boiling water 5 minutes.
Before beginning any canning recipe, prepare jars and lids as directed by the manufacturer. Ball recommends the following: “it is no longer necessary to pre-warm lids before use. If you desire, it is still safe to simmer your lids before use, however, you should never boil them.
Before using them, wash the lids by hand without dish soap in hot water. The lids are not dishwasher safe and must not be boiled before first use. It is important to know that the glass jars can be reused, while the lids must be changed for each new use in order to guarantee their hermetic seal.
You should allow lids to boil for at least 10 minutes to get the maximum sealing benefits. The lids will be sterilized and softened, which makes them easier to work with when you fill the jars with food. What is this? Overall, preparing jars for canning is simple, and doesn't take much time.
In order to actually sterilize jars, they need to be submerged in (covered by) boiling water for 10 minutes.
Instead, most experts suggest that you simply place the canning lids and their rings into water that is simmering, but not boiling for 10 minutes to thoroughly clean them.
Inversion Canning
Once secured, the jar is inverted (flipped upside down) and left to cool for several minutes before placed right side up. The thought behind the method is the hot food will sterilize the seal while creating a vacuum by allowing air to escape.
Place new lids (you must use new lids each time you do canning; bands can be reused if in good condition) in a small saucepan, cover with water and bring to a simmer (180°F). Lids must be simmered for 10 minutes to "activate" the sealing compound that helps achieve a vacuum seal.
While the old guidelines recommended dropping the lids in hot, simmering water before pulling them out and immediately sealing jars, Jarden now says it's not necessary to heat the lids in order to achieve a good seal. Instead, you can simply wash the lids and use them at room temperature.
Why can't you reuse mason jar lids?
You can reuse glass canning jars, but don't be tempted to reuse canning lids, she advises. The gasket compound in used lids may fail to seal on jars, resulting in unsafe food. When jars are processed, the gasket on new lids softens and flows slightly to cover the jar-sealing surface.
For best performance, lids should be purchased new each year (the sealing compound will break down on storage); although stored in a cool, dry location, lids stored up to three years may still seal. ✓ Under no circumstances should you reuse canning lids.

Every recipe is different, but you'll usually boil the filled jars for about 10 minutes. Once finished, shut off heat and remove canner lid allowing steam to escape away from you. Let jars rest in canner for 5 to 10 minutes.
Boiling newer lids may destroy the sealing compound and lead to seal failure. Warming the sealing compound before you apply the lids will not harm the lids and may help jars to seal.
Heat from a proper canning process is needed to make sure any microorganisms in the jar of food are killed.”
Place lids on jars, screw on rings and lower jars back into the pot of boiling water. The water should cover the jars; if not, add more. Boil jars for 10 minutes. Transfer jars to a folded towel and allow to cool for 12 hours; you should hear them making a pinging sound as they seal.
To sterilize empty jars, put them right side up on the rack in a boiling-water canner. Fill the canner and jars with hot (not boiling) water to 1 inch above the tops of the jars. Boil 10 minutes at altitudes of less than 1,000 ft. At higher elevations, boil 1 additional minute for each additional 1,000 ft.
For the lids: boil them in water for about 5 minutes to sterilise them. Do the same with Kilner Rubber Seals, do NOT be tempted to put them in the oven.
Place new lids (you must use new lids each time you do canning; bands can be reused if in good condition) in a small saucepan, cover with water and bring to a simmer (180°F). Lids must be simmered for 10 minutes to "activate" the sealing compound that helps achieve a vacuum seal.
Lids should not be sterilized but some say they must be hot: Submerge them in simmering water for 10 minutes (but feel free to skip this step if you're following the updated guidelines from Ball® Brand).