A rye species on strong water, preserved in the Natural History Museum Berlin. Strong water is an outdated term used to conserve organisms by storing them in a liquid (the strong water). Usually, one of two different liquids was meant to be:
Both methods have pros and cons. Ethanol is flammable and volatile and, if the pot is not hermetically closed, slowly evaporates.
Formaline (for example 5%) is colorless but toxic, carcinogenic and strongly irritating by inhalation. Formal preserved preparations are very hard due to the tanning effect of formalin. Formaline reacts with oxygen reactions which eventually lead to formation of formic acid; therefore, it is wise to add a small piece of marble to the formulation when formulating formalin to neutralize formed acids. Alternatively, buffered solutions can be used which is aimed at a pH of about 7.3.
The colors are irrevocably and often quite fast back in many preparations on strong water.
Nevertheless, almost all zoological and anatomical collections of non-microscopic species are composed of strong water samples. Most of the species with wet parts, such as fish, molluscs, spiders and some mammals, are stored in strong water. The main alternative, drying, leads to severe deformation; setting up only preserves the appearance and is very workable and depends on the expert's expertise. A relatively new but efficient technique is plastinization.
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