I am not an expert on the subject but I have read that it is because they were hand blown. That is where the tool that the glass blower used to blow air into the glass was attached.
Those bumps signify the mold that that particular bottle was made from. I verified it with Kerr Glass company when they wrote, "Dear Mary, Thank you for your interest in Kerr containers. Those bumps signify the mold that that particular bottle was made from." Sincerely . . . .
The most popular material for home canning jars is glass.
It is not safe to reuse commercial canning jars for home canning. The glass in home canning jars is thicker than in commercial jars and they are created specifically to work with 2-piece lids. It is also not advisable to use very old canning jars.
Blue Perfect Mason canning jars with the number 2 marked on the bottom are typically valued between $10 to $20, depending on the condition and rarity of the jar. Collectors often pay a premium for jars in good condition with clear glass and minimal defects.
To ensure proper preservation when canning, boil the jars for 10 minutes.
A canning kit generally includes wide-mouth canning jars, a funnel to fill the jars, and various utensils to handle the food you are canning. Some canning kits also come with a digital timer to measure processing time.
If you use fresh lids and the jars have been throughly cleaned and sanitized, you might be able to use them for canning.
To properly seal canning jars, you typically need to boil them for about 10 minutes.
You would want to have anything you're canning pretty hot when you put it in the jars, yes. Cold filling, sealing, and heating will cause jars to explode.
Yes, Mason canning jars are available at dry goods stores, grocery stores, and big box stores.
Canning jars should be boiled for 10 minutes before using them for preserving food.
Jars for canning should be boiled for 10 minutes to ensure the food inside is properly preserved.