Day 91-Midnight Blue Diamond Optic
Made in 2011, this is the only optic water bottle in Midnight Blue that I have ever seen. If you remember the post from Day 63, Midnight Blue is cased. See the photo below.
Water bottles are blown into a metal mold. Metal is used because the number of water bottles made makes it cost effective to pay the thousands of dollars that it would cost to have the metal mold made. To make optic water bottles the gather of glass is attached to the blowpipe and dropped into a different metal mold which imprints the ribs or the diamonds into the glass. The glass cools sufficiently enough to retain some of the pattern which is then blown into a water bottle mold. Below are the molds that produce the ribs and diamonds.
The molds which preform the optics in the glob of glass can be used to create optic patterns in almost any Blenko glass design.