Ok, so I had a few ideas for improving the gunmetal look on the handgun prop for Joy the other day and decided to give them a go.
I’d been experimenting with graphite powder on another project and mixed some with my airbrush flow medium (which seems to be some sort of thin water based acrylic, similar to aquadhere from what I can tell). I made a 1 part graphite to about 4 parts flow medium and 1 part water mixture and mixed well until it forms a thin grey liquid. Put this in my airbrush and ran a light mist over a matt black acrylic painted test surface. Dried it with my heat gun then rubbed half the surface with a coarse cloth. Sure enough the graphite gets polished on the rubbed areas and looks like shiny grey metal while the untouched surface has a darker dull lustre.
Next I tried it on the gun. The spray is so light you can spray right over all surfaces including non-black areas and it wont affect them very much, in fact it adds a thin layer of surface aging/grime which can be a good thing if the prop looks “too new”. If you dont want it somewhere you can either mask out or just rub it off later with a moist cloth and/or bud.
I liked the effect but it was still a little bit to subtle in places, I wanted to get the inner surfaces looking even more dull and aged. To do this I made a similar mixture except with black powder paint instead of the graphite and sprayed this into the places I wanted dulled down, avoiding my freshly polished surfaces where possible. The black is dried (again, it is so light that the sprayed areas blend with unsprayed surfaces quite evenly) then any excess removed with a damp bud.
Later, I went over places I wanted heavy dulling with a brush loaded with the mixture, almost like a wash or ink. You can be quite imprecise as it dries quite evenly because it is thin.
All in all a much more realistic and durable effect than the simple graphite rub I was using before. Obviously, now that I know this works I’d reverse the process in future doing the dulling first then the highlights/polishing.