11 mm Gras ---- wax in the case

I pulled a 11 mm Gras cartridge (lead bullet, SFM * GG *) and found some wax between the bullet and the cardboard before the powder.

What wasits purpose? I think that it could lubricate the barrel. Was it used on every Gras cartridge?

When loading any of the black powder cartridges, back in the days of the Gras, Comblain, 11mm Mauser, Martini-Henry, the American Springfield cartridges, etc., or now, duplicating those loads, it was (and is) necessary to fill the case completely and to slightly compress the black powder. Air spaces could lead to accidents upon firing. Better accuracy was achieved if a wad was placed between the powder and the base of the bullet. This prevented the burning powder from deforming the bullet base. It was also common practice to place a lubricating wad between the over-powder wad and the bullet base. This kept the black powder fouling soft and lubricated the barrel for the following shot.

There were many scores of recipes for making lubricating wads. With a little persistence, you can find them posted on the net. Sometimes the wads were lubricated felt, sometimes simply a waxy or grease concoction. Waxes of many types were used as a principal component. Even today, such wads are sold commercially