Re: Are the lens of eyeglasses made of powder?

The most common lens material manufactured for eyeglasses is a form of plastic polymer called CR-39. Chemically the polymer is called allyl diglycol carbonate. It is used for lenses because it has almost the same physical properties as optical glass but is a much lighter material. This makes is ideal for glasses since the most common complaint about eyeglasses made from glass lenses is the heavy weight of the glasses.

Now, on to the answer to your question. All polymeric plastics are typically made from either liquid or solid polymer material heated and then molded into the final form of the plastic product. In the case of eyeglass ware, and in particular, CR-39, the block lens material before it is made into the final lenses is made from small plastic pellets called resin pellets. These pellets are melted to form a liquid and then poured or injected into a mold to form a block roughly the shape of the lens. This block is then ground down and polished into the finished lens that then goes into the glasses frame. The process of melting the resin into the block plastic forms a solid block of material with no physical gaps in block. The ability of a plastic to absorb liquid or gas is a property of the polymeric material called permeability. All plastic materials have known, measurable permeability to gases primarily and liquids secondarily. In the case of eyeglass lenses this is more often associated with the coating on the lens rather than the lens material itself.

Therefore, the ability of eyeglass lenses to absorb water or other material is a property of the chemical polymeric material the lens is made from and the chemical material the lens-coating is made from. Any absorption of liquid by the material is a propery of the plastic and not the way the lens was made.