Around the time of the American Civil War, syrup makers started using large, flat sheet metal pans as they were more efficient for boiling than heavy, rounded iron kettles, because of a greater surface area for evaporation.
Storing Maple Syrup
Pure Maine maple syrup contains no preservatives and should be refrigerated or kept in a cool dry place after the seal is broken. Properly prepared maple syrup will not freeze, and the freezer makes an ideal storage place.
It also may be heated to 180 degrees and canned in sterilized jars. Process pints in boiling water for 10 minutes.