The application of flotation for the separation of plastic mixtures derived from post-consumer waste is relatively new, the earliest publications on this subject date back to the late seventies. Flotation was originally developed for ore separation about a century ago. Early research studies on plastics flotation were concerned with testing surfactants known from ore flotation. While searching for suitable wetting agents has been the principal research subject in this field, it became clear later that other surface treatments can also be utilised. This paper is the first part of a critical review on available literature data of plastic flotation research from the last three decades. It is felt that there is a need for such a review, because there is still considerable interest for this technique to separate plastics but literature data are often presented in the light of conflicting theories. Part I gives a brief overview of suitable methods to obtain selective flotation of different kinds of plastic and discusses the liquid-vapour surface tension control method in detail. (C) 2003 Elsevier Ltd. All rights reserved.