Pushing all the buttons

In trying to find suitable materials for my workshop with 7 year olds, I was dismayed to find out how much mosiac glass cost and how hard it turns out to be to find small square ceramic tiles. Although I have collected quite a bit of crockery, happenstance has not provided me a full range of color and I fretted over the sharp points of broken shards in young hands. I was almost ready to resort to beans, lentils and macaroni shapes when it dawned on me. Clothes buttons. Cheap, hardy and suitable for the north side....wait. Cheap (a two dollar bag will cover a lot of space!), easy to handle and they come in all colors. They have the added benefit of being much lighter than tile and should be fairly permanent, being made mostly of hard plastic. Some of them also have amusing details, such as a heart or flower shape or designer's name. They also range in diameter from tiny to huge but have just about the same depth. And while the color red was a rare exception in ceramic tile, the buttons' problem color turns out to be green. Huh. Send me your buttons....