The history of condensation nucleus counters

Condensation of supersaturated vapors has been used for more than a century to grow small aerosol particles to sizes that can be detected optically. T his paper discusses the history of instruments that use condensation to det ect particles. I divide this history into two main sections. The first of t hese focuses on the development of expansion-type instruments including the "dust counters" in which John Aitken played the decisive role and "photoel ectric nucleus counters" primarily by L. W. Pollak and coworkers. The secon d section deals with the development of steady-flow condensation nucleus co unters (CNCs) in which Jean Bricard and coworkers played the decisive role. The importance of calibration methodologies is also pointed out. Refinemen ts by instrumentation manufacturers and many aerosol scientists have led to the reliable, accurate instruments that are widely used today.