TwiceBarrel, not so sure about your comment that Case colors don't fade. I would think that oxidation and ultra violet rays must have some impact on them.
Maybe some experts in the Case Coloring arena can comment.
Yes, UV deteriorates Case Colors ........while discussing this same topic a few years back, Ken Hurst (ex Colt engraver) posted that Colt changed out certain SAA's annually in their showroom because of UV case color loss, caused by the UV in their flourescent lighting.
Clear lacquer over the surface of case colors
does nothing to stop the UV deterioration and usually yellows badly after a couple of years. It just made the case colors "shine" a little bit for the new buyer.....
Sunlight directly entering the old glass faced gun cabinets would deteriorate case colors......very common and very well understood in the industry.....
Obviously cleaning with anything abrasive will deteriorate the colors as well, as case colors are a thin colored skin with shallow penetration near the surface of the metal. Many customers want "distressed and weakened colors" so many smiths use various cocktails to rub on the surface of new CCH thereby dulling the colors. Mother's alloy wheel polish works well for this type application, used sparingly and by rubbing lightly of course.
For most metal surfaces, older guns that are used suffer most from "sweaty hands" over the years. Browning used to publish in their owners manuals about sweat and finger prints, recommending that owners clean them off immediately after use or handling and even included a special yellow treated rag with each new gun. Sweat is especially brutal on rust blueing......sweat contains salt and can make your guns look like a N.Y. taxi pronto.
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This particular LC was shipped from the factory in August 1914 and still shows about 50/60% factory case color coverage, although the colors have dimmed over the years from UV as mentioned above.


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Re-Cased and restored 1926 LC, I completed it in 2007......weekly shooter ever since......



Best,