brown spots on a brass locomotive

[Schraddel]

Hello,

no effects known to me. When to model is painted the tarnish disappears completely.
What it is: <!-- m --><a class="postlink" href="https://en.wikipedia.org/wiki/Tarnish">https://en.wikipedia.org/wiki/Tarnish</a><!-- m -->
With our brass locos the tarnished spots are caused by imperfections in the coat of protective laquer. Note, even the "unpainted" loco were spayed over with a coat of clear or gold coloured laquer. This is to prevent the brass surface becoming dull within weeks.


Even in this very worst case, here foam decomposition which caused copper rust and real cavity spots into the brass surface...





... they disappear simply after painting. There is no necessity to polish the tarnished before.