Why No Direct Sunlight?
You should never put something with a lot of clear glass in the direct sunlight. Why? Glass acts as a prism which acts like a magnifying glass and can start a fire. The sunlight will never harm or fade your glass piece. When glass is blown it's heated to 2500 degrees. You can put your pieces outside but not on anything that can reflect and create a prism. I put them around my pool on a plastic table or under an umbrella. You can also use them in a garden on a garden stake.