Answer from Radleys FAQ : It is recommended that Findenser is cleaned after use using the following protocol: • Flush the internal glass surfaces with a suitable cleaning solvent such as acetone or IMS. This is best achieved with a wash bottle. External exposed glass surfaces may also be cleaned with a suitable solvent. • Allow washing solvent to drain into a suitable receptacle. • Wash the whole Findenser assembly in warm soapy water, using a soft brush to clean fins. • Rinse with warm water both internally and externally. • Allow to air dry. • If necessary, Findenser may be cleaned in a dishwasher. However care must be taken to limit the temperature of the wash cycle to 50˚C.