Some history...
Purple glass was manufactured between 1880 and 1914. The manufacturing process included the addition of manganese to produce clear glass. However when this glass was exposed to the ultra-violet rays of the sun, it turned to an amethyst color. This process was used until 1914 when World War I cut off the supply of manganese from Germany. Most of my pieces are a light amethyst, but some can achieve a deep purple color depending on how much manganese was added to a particular batch.
I'm not sure if I exposed my pieces to the sun if they'd darken. Hmmm...maybe I'll try it with one of the smaller ones.
We had a wonderful visit with Mom & Dad. I'm so glad that they were able to come visit...even if it did take them two days to drive across Texas. They didn't go home that way, however.