As far as I know, "made of" is used when the material doesn't change but when it is transformed "made from" should be used. However, I came across the following sentence while reading an article on "eating out in restaurants" in an FCE book:
"... fortunately, all (wine) glasses are made from unbreakable glass."
I don't understand why "made from" is used here while glass is still glass. Can you offer a logical explanation?
NOTE: I've already studied previous similar questions but couldn't find an answer.