Frosty white sea glass can be very pretty and surprisingly pristine. White sea glass was originally clear glass with a surface veneer that has become cloudy white with pitting and "sanding" from years in the surf. Many liquor bottles were created in this color in the early 1900's.
Machine-made bottles with colorless glass can date from any time after 1905, though there is a relatively reliable dating break possible based on the type of colorless glass. In the production of colorless glass numerous methods - mechanical, physical, and/or chemical - were used to decolorize glass (Tooley 1953). Decolorizing is in essence neutralizing the effects of the iron and carbonaceous impurities in the glass mix in order to obtain as colorless of glass as possible. The primary physical (masking) agents used in the first half of the 20th century were manganese dioxide, selenium, and arsenic. All potentially leave a very slight residual color to the glass that is usually visible when looking closely at the thickest portion of the base or sides. -Society for Historic Archaeology