I recently collaborated with Andy George and his fascinating How to Make Everything youtube channel on a project. I helped Andy to make glass from scratch, using only the raw ingredients you can gather yourself from the natural environment. You can collect silica from sand, potash from wood ashes, and lime from chalk or limestone. Andy then ground his glass into lenses for a pair of spectacles. Have a watch of the video below here! There’s also a follow-on video with cartoon animations on why glass was so critical in the history of us developing science.