[ARC5] Why Wrinkle Paint?

[Robert Eleazer]

Why?  Well it was in the specification, and therein lies a great deal, sometimes including nonsense.

The USAF was building a space control center back in the early 1980's and specified leather upholstery for the chairs.  Leather is a nice durable covering that does not promote static charge buildup, so that was reasonable.  And naturally someone looked up the MILSPEC for leather and specified that.

And then they found out that MILSPEC required the leather curing process to include piling horse manure on the leather and letting it sit for a month.  No one knew why they needed to do that, but eventually it turned out that the leather MILSPEC originally was intended for saddles for the US Calvary.  And horses like saddles much better if they really, really smell like horses - hence the manure treatment.

Also, a standard military spec requirement for electronics is that a hipot test be done at not less than 550V or so.  This makes sense for tube gear but doing that with solid state gear is asking for trouble (there is an alternative test specified for aircraft instruments that allows you to use twice the operating voltage but not less than 125V, and I used to specify that).

I do think that wrinkle finish - used for many other things than military radios - is a durable finish that is lighter than the alternative of putting on multiple coats of primer followed by topcoats. 

It appears to me that in some cases after WWII the paint for military airborne electronics was switched to lacquer.  For example, my APR-4Y looks like it uses some black lacquer on the front, while the case cover is a fine black wrinkle finish.      


Wayne
WB5WSV