The best treatment is leaving a holster alone.
That said, when I get a particularly dry of slightly flaking example, I find that using a very small amount of Kiwi shoepolish (we are talking 'very small amounts' here, and only Kiwi) on the exposed parts, together with a good old dry brush helps to revive the leather without doing too much harm to it. It helps to camoflage part where the original dye has faded with little or no long term effects.
The stuff comes in black and brown, and the brown will conform itself to the original holster color.
I usually clean out the inside with an alcohol patch. When a holster is really messed up (like many former Norwegian ones are), I use an alcohol moistened piece of soft cloth to remove the many years of Norwegian army shoepolish that usually covers the holster. Followed by the treatment described above.
When it comes to treating leather, less is more and subtleness is the key.
The 1916 holster shown was a complete shoepolish encrusted Norwegian wreck when I got it.
The 1918 holster was starting to flake, with some scattered parts of exposed leather where the top layer had disappeared.
These holsters are dry, not mushy in any way and even retain their old smell, which returns after a couple of days afte treatment.
|