It has been shown that the organic contaminants released during the carbonate and binder decomposition of conventional oxide cathodes can be eliminated if the cathode is preconverted in a separate envelope and is then transferred to the final tube as the alkaline‐earth hydroxide. The technique used in accomplishing this lends itself readily to many laboratory applications where tube cleanliness is important. Specific applications to thermionic and secondary emission studies are described. The results indicate a definite reduction in the contamination of tube components and show improved cathode characteristics.