Salt-Mask Weathering (Part 1) - A New Experiment in Weathering

Although, a little late to celebrate the 200th blog post, I'm going to show a technique that I'm starting to experiment with.  This certainly's not a "Here's how it's done" post, but more documenting my experimenting with the first six or so cars using this technique on the roofs.

Salt-Mask Weathering

Salt-Masking with a light wash of acrylic dust/dirt paint over the top on SPMW 2257's roof.

For many years I've seen great modelers using this technique to very believable effect.  I'd never tried it, so this year I decided to dive in with some of my new boxcar projects and see what I could do.

Round 1 - Yardmaster Roofs

I painted the roofs with DRGW MW Gray

I purposely was a little spotty with the application with the airbrush of the MW Gray to make some variations in the finished undercoat later.

Adding some rust to the top of the gray galvanizing color.

On these roofs, I decided to try doing some variations in pre-weathering, which will be under the salt-masked application of the SP FCR paint.

Other two roofs with weathering before salt-mask applied.

Running Board Masked

Salt applied and masking applied

On the Branchline Yardmaster roofs, I masked off the running boards to prevent salt-masking on them.

Another roof.

Painting Roofs

Freight Car Red applied to one of the roofs.

It was painting these roofs that I realized that the over-coating paint really has to go on dry, so as not to stick the salt to the roof with the paint!

All three roofs with salt and painted.

Scrubbing Salt-Mask Off

Branchline YM Roof for P&LE 30423.

The black paint original paint "burned through" the FCR and MW Gray with hard scrubbing with the toothbrush.

One of the two SP B-50-21/23 Branchline YM roofs.

The second SP B-50-21/23 Branchline YM roof.

Round 2 - Red Caboose SP B-50-18/19

Pre-weathering to RC boxcar roof.

On the Red Caboose B-50-18/19 I didn't do a full roof gray paint, but only selected areas, which means the salt-mask with the FCR overcoat will be less noticable.

Salt and paint applied to Red Caboose cars.

Scrubbing Salt-Mask Off

One of the RC B-50-18/19 roofs after salt-mask is removed.

The other RC B-50-18/19 roofs after salt-mask is removed.

Accurail Boxcar

Wetted roof applying salt

I think this car got too much water on, and the salt partly dissolved, which caused issues with getting the salt off after painting.

Roof dried with salt-cake in place.

Quite a bit of salt has caked in several places.  I found that it is possible to knock some of the excess off after the salt has dried in place.

SP FCR paint applied and salt knocked off.

SP 26948 - B-50-12 Roof Weathering

Pre-weathering to SP 26948's roof

Tichy USRA/B-50-12 roof after salt-mask removed.

The SP 26948 salt-mask was painted a little too wet, which results in salt being stuck in the paint, which is actually adding 3d shape to the paint surface.  I'm not sure how well this will last in the long terms with the interaction of the paint, salt, and plastic roof.

3rd Round - Iso-Alcohol?

SPMW 2257 - B-50-2 - Outside Metal Roof

Pre-painted roof with a base gray used.

This time I tried spraying the roofs with a Testors gray enamel paint.  Left models out in the sun for about 15-20 minutes to bake the paint.

70% Isopropyl Alcohol wetted roof of SPMW 2257

This time I tried Iso Alcohol instead of water, which has better "wetting" characteristics and lower surface tension.  This should allow the salt to stick in smaller clumps and not have the large areas of masking happening, as happened some times before.

Dried salt in place on the roof.

Salt applied to Iso Alcohol wetted roof.  I think the salt still pulled the Iso together, making it act like surface tension.  I'm still working out how to wet the roofs without pooling the liquid, and having the salt clump up.

Finished salt-mask on SPMW 2257

This salt mask resulted in some interesting clumps of salt-mask and some areas that didn't get much mask at all, which is how it goes.

SP 32451 - B-50-15 Murphy Radial Roof

Salt mask on SP 32451

I thought this salt-mask was good on the SP 32451...

Finished salt-mask on SP 32451's roof.

...but there seems to be a bit more masked than I wanted... I'll probably go back with another round on the areas that were over-masked.

NC&StL 15337 - Fowler Out-Side Metal Roof

First try salt-masking NC&StL 15337.

Obviously I got a bit too much salt on some of the mid-car panels!  I may go back and remask some of these spots and then paint again.

In Closing

SP 84550, SP 38542, SP 96311 (top row), SPMW 2257, SP 32891 (mid row), PLE 30423, SP 26948, SP 32451 (bottom row)

So far the salt-masking has been fun, and I certainly can see how this can and will make some awesome roof weathering.  I think I need to do more examples and also experiment with other pre-weathering before applying the salt-mask and also possibly doing multiple salt masks to simulate paint failing and the galvanizing failing and rusting below the paint.

Jason Hill

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ATSF 129782 Bx-38 - Weathering with Pencils and Acrylics - IMRC WWII Emergency Boxcar

Weathering SP Steam Engines (Part 1) - Overview and Basic Techniques