> We most certainly >know the temperature when yeasts are killed. Any wine maker is familiar with >the temperature 100F. We also know the temperature many other contents of >honey are ruined (Honey - E. Crane). The processes in question are chemical reactions. The extent to which they proceed - how much of the reactants get converted to how much products - depends on not only the T but also the t. Even the crudest rule of thumb for how much a chemical reaction is promoted by heating must include an indication of both temp AND time. In order to begin thinking about such matters one must form some concept of a T-t combination. Taking the matter even further away from simple rules-of-thumb is the fact that in nearly all actual cases these two influences are not simply reciprocal so you can't use anything like "double the temp and that'll let me halve the time". Few of the responses are linear, so that doubled time may give, say, quadrupled extent of reaction; dependences on temp are exponential, but the steepness of the graph differs from one reaction to another; etc. This is an area of physical chemistry & biochemistry in which rules of thumb are very hard to come by. What you end up with, where possible, is empirical rules based on a lot of actual measurements and a margin for safety e.g. 'all microbes are killed by steam at 121 C for 20min.' (a common rule of thumb for autoclaving). More delicate matters, which are the main interest in processing honey, are more tricky. R - Robt Mann consultant ecologist P O Box 28878 Remuera, Auckland 1005, New Zealand (9) 524 2949