Preparation of wood for microscopic analysis after decay testing

摘要

A new method of simultaneous staining to identify the prevailing type of decay in samples after biological testing. Field tests and laboratory experiments with a natural composition of different factors causing degradation are gaining more and more in importance, especially for the determination of the effectiveness of new treatments for wood protection. The European standards EN 252, ENV 807 and ENV 12037 take this into account. In test methods with close relation to reality, a large number of various stresses and organisms occur parallel to each other and in succession. By microscopic investigation the prevailing types of decay and the special weaknesses of the treatment tested can be identified. In the following a method for preparing wood for microscopic analysis after decay testing will be described, with special regard to a new simultaneous staining, which helps to identify types of decay. The method proved to be successful in microscopic examinations after biological testing of Pinus sylvestris L. and Fagus sylvatica L. untreated and modified with melamine resins (Rapp and Peek 1996, Rapp 1997). It is suitable for simple hand sections as well as for microtome sections of specimens, previously embedded in polyethylene glycol (PEG) and picked up during the cutting process by transparent adhesive tape.