[ARC5] Satin finishing aluminum

[Mike Hanz]

> Does anyone know how aluminum was processed to achieve the satin finish typical
> of ARC-5s and similar WW II gear?

An aluminum etching solution - prior to attachment of any subassemblies 
like rivet posts.  This was done in the plating department, from what 
I've been able to determine.

> How about restoring such a finish?

The difficulty I've run into is incompatibility with anything else 
mounted on whatever you are trying to restore.  IF (big if) the part is 
*all* aluminum, the most benign etchant I've discovered is Scrubbing 
Bubbles, believe it or not.  The caution is that if the solution can get 
into any interfaces between, for example, riveted parts, it will keep 
working as an etching solution for years to come.  There are more 
aggressive solutions available if the part has no extraneous pieces 
added onto it - I use a fair amount of the automotive enchants (Sherwin 
Williams W4K 263 Dual Etch is one example) but they do require some 
experimentation, and if you try 'painting' the solution on the part, you 
need to keep the part wet until you've achieved the desired 'softness' 
in appearance.  In my experience with fighting this battle, the best 
results were obtained by polishing the aluminum to a mirror finish and 
then applying the etchant.  YMMV

Best wishes,
Mike