Excessive use of passive constructions seems artificial and uncomfortable to readers. On top of this, ambiguity and confusion are often added because passive constructions often do not specify clearly who was the actor or agent in an event. I misunderstood all the following extracts on first reading:

1 Smith and Robinson have determined the extent of thermal degradation by heating for standard times at 220°C and then calculating the weight loss during this time, together with the changes occurring in the infra-red spectrum of the polymers. The colour of the polymers has also been reported, as it gives some guide to the extent of the reaction. This stage of the investigation is nearing completion, and it is planned to examine the products of pyrolysis in the region of the exotherm using gas chromatography.