Unused resin and hardener (unmixed) are not waste and may be saved for future projects as they have a long shelf life. Cured epoxy resin (completely solidified) may be disposed of as non-hazardous waste in most municipalities. (Check with your local waste management requirements.)
Containers and tools may be reused if cleaned with lacquer thinner, acetone, or rubbing alcohol (in a well-ventilated area). Disposable containers, brushes, etc. may also be thrown away safely once the polymer has cured completely.
