The wide mouthed bottle allows for simple hand washing. For best performance, we recommend washing the bottle and lid by hand. You can remove all normal contamination from the material using a non metal bottle brush, similar to the OXO Tot Bottle Brush. Do not use carbon steel brushes, or brushes with a metal rod or tip that can scratch your bottle. The oxide barrier can be breached and will then need to be treated correctly, otherwise you'll think you just cleaned your bottle, only to have it rust on you. If your bottle shows signs of rust, you can re-treat the surface with a citric acid bath. Citric acid is 100% environmentally friendly and doesn't require special equipment to handle.