I found this in Wm. Duane's Hand Book for Riflemen (1812)
It is titled "To Preserve the Rifle from Rust" but the author expands on the importance of camouflage.
It is a camphor-based solution and like the Prof. pointed out, appears to be heavily "borrowed" from British manuals.
Here is the recipe. Start with:
1 oz. Camphor
1 gill. Oil of turpentine
1 gill. Florence oil (Florentine olive oil)
Simmer over an open flame in an earthen cup until the mix is incorporated in a uniform state, putting in the camphor last.
Next, add in an ounce of clean, white bees wax. Melt the whole adding in a little sweet oil (virgin olive oil) or turpentine.
For Color:
* Blacked - Add about an ounce of powdered black lead (graphite)
* Browned - Add about an ounce of red lead oxide (yes, it?s very toxic especially as a powder) or red ochre
* Greened - Add about an ounce of powdered verdigris
* Blued - Add about an ounce of Prussian Blue (made from oxidation of ferrous ferrocyanide salts & still available today)
The mixture is applied warm onto the bare metal and rubbed in evenly.
I am thinking about getting a Southern Rifle kit from Track of the Wolf and doing up the metal. I'll use a dark stain on the wood. I am really intrigued about something that exists in historical texts but is almost unheard of today. I have a feeling that as historically accurate it may be, it's also going to be ugly to our modern muzzloader's eyes.