Soda Lime.

Q: I recently acquired a fancy glass bead, and had no idea what it was. I took it to a local glassblower who said it was "soda lime glass". Not wanting to appear ignorant, I thanked the man and left. Now to be ignorant... what is "soda lime glass"? Is this good?

A: Calcined limestone, which added to the glass batch in small quantities, gives stability. Before the 17th century, when its beneficial effects became known, lime was introduced fortuitously as an impurity in the raw materials. Insufficient lime can cause crizzling. Soda-lime glass is the most common (90% of glass made), and least expensive form of glass. It usually contains 60-75% silica, 12-18% soda, and 5-12% lime. Resistance to high temperatures and sudden changes of temperature are not good, and resistance to corrosive chemicals is only fair. It's Glass. LOL I guess he was trying to distinguish that the bead wasn't something special like "lead crystal" - and not something like 'Pyrex'. The majority of glass today is 'soda lime glass'. Basically, he was saying it was just "common glass." However, the TYPE of glass is not necessarily what drives the value of the bead. Age, style, color, form - beauty.... those are the important things about beads. So - tell us more about your bead.... It must have been "special" for you to be so attracted to buy it before you knew anything about it.