Experiment time!!!!! So I found a crappy old plastic atlas bridge and decided that I would try weathering it a few different ways to see which way I liked the best. The winningest technique will be what I use on a much more expensive metal bridge.
First, I sprayed the plastic with Krylon Colour Master Primer Red Oxide Ultraflat.
Christian Maheu suggested that I use my airbrush to add some different tints of rust on top of the primer with dark brown acrylic paints to give it some depth. You can see the result in the bottom of the two bridges in the image below.
Next up I will try weathering it with the following scenarios:
1. Hairspray technique
2. Salt technique
3. Rubber cement
Hairspray Weathering Technique
This was the technique that the majority of people liked the best. And I have to agree. Here is how it works… Paint the base colour, which in my case was the red oxide primer, and let it dry. Then spray cheap hair spray (I used Silkience Pump Hairspray) over the entire area. Once the hairspray dries completely, coat it again with hairspray and let that dry. Do not rush this. Then airbrush black acrylic paint on top of the hairspray and let that dry.
Next take a wet paintbrush and very gently rub the black paint off. I was amazed at how quickly and easily the black started to flake off and peel. Careful not to overdo this. LESS IS MORE. The result below still needs a spray of dullcote but you get the general idea.
Here is a great video tutorial on the Hairspray method.
Salt Weathering Technique
This was everyone’s second favourite method. It’s also super easy. Like the Hairspray technique I started with the same base coat of Krylon primer and airbrushed brown acrylic paint. This time, I sprayed the entire area with water containing a little 70% isopropyl alcohol. Then simply sprinkle coarsely ground sea salt (or in this case Himalayan Pink Salt that I stole from the kitchen) over top of the bridge. Let the salt dry completely. Once dried, airbrush black acrylic paint on top of the salt and let that dry as well. Then is it simple a matter of running the salt under some warm water to dissolve the crystals. NOTE: I did not have any luck rubbing the salt off, the water worked much better.
Here is a great video tutorial on the salt method.
Finally I tried using rubber cement on top of the base coat instead of salt to see if I could control the area to peel off and while it did give better control, the result wasn’t as satisfying.
A number of people have suggested that I combine methods and that may be my next experiment!