The author has shown by experiments that particulate ammonium sulfate and other salts from the atmosphere can be deposited on paint fllms by thermal precipitation. The presence of water on the surface was not found to be essential for the deposition to take place. This shows that the formation of ammonium sulfate from sulfur dioxide, ammonia and atmospheric oxygen in condensed droplets of moisture is not the only mechanism which will give rise to ammonium sulfate bloom on paint films. -- AATA