Ball® Canning & RecipesTeam we have determined that it is no longer necessary to 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. To prep lids we recommend simply hand washing them in hot soapy water. Please let us know if you have any questions or concerns! We always love to hear from our awesome fans.
Here's the answer they emailed back to me
Thank you for contacting us! We apologize for the delay in response.
After many years of research, it was determined that preheating Ball, Kerr, and Golden Harvest lids is no longer necessary. The sealing compound used for our home canning lids performs equally well at room temperature as it does pre-heated in simmering water (180° F). Simply wash lids in hot, soapy water, dry, and set aside until needed.
Instructions on the lid, cap, and jar packaging has been changed. However, retail stores may still stock packaging having either instruction.
We hope this information has been of assistance. Again, thank you for contacting us.
The Consumer Affairs Team
With that being said, here is my personal recommendation:
Concerning the New Lid Procedure: My advice it to continue to warm your lids. I have not had an issue, but I am not following the new procedure. if you notice in the answer that Ball posted in response to the question about this on their face book page, they say it is still ok to simmer but not necessary. I still pour boiling water over my lids and let them sit in the water until I am ready to use them. I don't boil them, just pour the water over them. Maybe further testing needs to be done, I don't know. They said that the new lids work just as well at room temperature, but I have had friends having problems with seals breaking so I still believe that heating the lids gives you a better seal. Of course you don't have to, this is just my suggestion.