Here you get all information about the care and maintenance of your Böhm Stirling engines.

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Sureface oxidation and aging

The brass will tarnish which is intended. Your model will get a patina and this will darken with time. Fingerprints can be seen but will also darken. Oxidation is no reason to make a complaint. Brass is subject to natural oxidation processes. 

Avoid contact with sweaty palms, water and moisture. The brass can be polished with standard polishes! Allow the models to age normally. After a few years, they have the desired brass patina.