Feeling Blue Those blue mason jars were mass produced until 1937 using sand from around Lake Michigan. It was that sand that gave the glass its blue hue.

Is it safe to can salsa in a water bath?

Without the addition of the correct amount of acid, salsa is considered a low acid food. Low acid are not safe to can in a hot water bath canner due to the potential threat of pathogens like Clostridium Botulinum, the bacteria that causes botulism which can be fatal (read more here).