How can you tell if your eye glass lenses are plastic or glass?
You very seldom see any lenses made of glass these days, they are very heavy, and most places that make eye-glasses will do their best to try to talk you out of getting glass lenses due to any possible injuries that are more prone to occur with glass. Plastic is much lighter, and much safer.
Lens are made of plastic. Glass is heavy and you would notice the nose pieces digging into your nose if your lens were made from plastic. Of course if you really wanted to be sure take them into a optician' s office. They have them in the mall and else where.
Temperature -- Glass holds its temperature more. Compare the feel of anything in a glass jar the fridge to something in plastic. Glass feels cooler than plastic. Or hotter if just out of the dish washer. If you touch a piece of plastic to your cheek it will usually feel room temperature, whereas if you do the same with a piece of room temperature glass it will usually feel somewhat cold. Also these days they don't drill holes in glass lenses to attach frames anymore, so if they have a hole to hold the lenses in place then they are plastic. (Unless they were made before the 1980's) Another way to tell the difference between glass & plastic is to tap it with your teeth...
I disagree with Heaven4441. Glass lenses are better than plastic, especially for strong prescriptions. My ex-husband has very poor vision & needs strong lenses. We found that his glasses didn't need to be as thick if he had his lenses made of glass instead of plastic. Also, glasses made from glass don't scratch as easily, so they last longer. And a third reason to buy glass lenses instead of plastic lenses is if you like the type of lenses that turn dark in the sunshine & get lighter in the shade this treatment works much better & responds quicker on glass.
Don't let anyone tell you that glass lenses aren't safe. They are just as safe as plastic. In fact some safety glasses are made of glass. I especially like the way that glass lenses don't scratch as easily as plastic. This means they tend to last longer because they are more durable & will stay clear & scratch-free for years.
One problem with glass lenses is, if you like larger lenses they can be quite heavy. So if you like the "Nicole Richie" bug-eyed look you should buy plastic lenses because large glass lenses can be a bit heavy & take some getting used to. But if you like your lenses to be small or medium in size then it's no big deal, they won't be very heavy.
Because of the experience I had with my ex-husband buying glass lenses I had my partner try on some glass lenses. In the past he had always worn plastic lenses, but now that he's owned several pairs of glass lenses, he's hooked! You don't have to worry about how you set them down because the lenses rarely scratch (unlike with plastic), & believe me when I say that the type of lenses that turn into sunglasses work much quicker & better if they are made of glass.
We're just going to have to agree to disagree on this issue. I stand behind what I said about glass lenses as opposed to plastic. Each have their own advantages, but plastic IS safer. The place where I have my glasses prescriptions filled, make me sign a waver that they won't be held responsible for any damages if I should happen to order glass lenses as opposed to plastic.
They wouldn't insist that I do this if they weren't worried about being sued in the event of glass breakage. In your husband's case, maybe the best thing WAS for him to buy glass, but for the most part, plastic is encouraged and recommended by the people who actually make the eye-glasses.
The question from the man was , "how can I tell if my glasses are made of plastic or glass?", not a philosophical debate on which is better. I just know what the people who make MY eye-glasses say whenever I mention that I would like to order glass lenses so that they can change from sunglasses to regular glasses automatically, (glass is the only option for this feature). I inevitably wind up with regular glasses, as well as a pair of prescription sunglasses, due to the concern of the eye-glass company.