Realistic Truss Bridge Weathering

I do all my weathering after assembly of a kit.  In the case of your truss bridge, you should be able to reach all the visible areas with a long stiff brush to apply weathering chalk.  I would concentrate your efforts on the visible areas (top and outside edges).  If a structure is only visible from one side, I only weather that side.  

You already did the most important step:  Painting.  The chalk will not stick to bare plastic or the glossy paints that manufacturers use.  You can use plain artist's chalks (I think that is what Joey uses), but weathering chalks from Bragdon's and Doc Brown add powdered glue which greatly helps with adhesion.  There is no need to add a clear coating (which ends up toning down the weathering way too much).

I apply 2 shades of rust, most heavily at gusset plates, rivets, anywhere metal attaches to metal, and anywhere water might collect.  Leave some areas untouched for variety.

Here is a Steel Trestle I built and weathered.

Bob

You could try a liquid rusting solution such as that made by Model Tech Studios. I've used a small brush, toothpick and Q-tip to apply it, depending on the situation. It will definitely get down into tight areas.

Sometimes it comes out a little too bright orangey-colored, but you can then reduce the gloss by applying their aging solution and/or a dark colored (black or charcoal) chalk or flat black paint over it.

Consider salt weathering. Eric Siegel does a tutorial in his video series - Episode 37.

Bob

Dip the brush in paint, then in chalk and dab it on.

@RRDOC posted:

I do all my weathering after assembly of a kit.  In the case of your truss bridge, you should be able to reach all the visible areas with a long stiff brush to apply weathering chalk.  I would concentrate your efforts on the visible areas (top and outside edges).  If a structure is only visible from one side, I only weather that side.  

You already did the most important step:  Painting.  The chalk will not stick to bare plastic or the glossy paints that manufacturers use.  You can use plain artist's chalks (I think that is what Joey uses), but weathering chalks from Bragdon's and Doc Brown add powdered glue which greatly helps with adhesion.  There is no need to add a clear coating (which ends up toning down the weathering way too much).

I apply 2 shades of rust, most heavily at gusset plates, rivets, anywhere metal attaches to metal, and anywhere water might collect.  Leave some areas untouched for variety.

Here is a Steel Trestle I built and weathered.

Bob

Not to derail the thread, but where/how did you get those awesome bridge towers?  Kit? Scratch built?  

The towers were built from Central Valley HO lattice girder components and sheet styrene, the plate girders are from Scenic Express, footers are cast in plaster, and the deck is plywood. Construction details are in a 2-part article in O Scale Trains March/April 2023 and July/August 2023.

Bob

@RRDOC posted:

The towers were built from Central Valley HO lattice girder components and sheet styrene, the plate girders are from Scenic Express, footers are cast in plaster, and the deck is plywood. Construction details are in a 2-part article in O Scale Trains March/April 2023 and July/August 2023.

Bob

Thanks, Bob. They are very well done. I’ll go find your article.