--Originally posted September 8, 2008--

"SALT TRICK" Paint-Flaking: Bench Tests

Searching for a method to depict chipped paint on my Type 96 Nell build - though, in the end I did not use this on that build - I was able finally to test out this long-pondered technique:


Learned right here on this Board (Thanks, Dave!), this technique employs ordinary table salt (NaCl):


Click on Image to EnlargeThe idea being to paint a desired undercoat - for aircraft, usually a simulation of a bare metal (aluminum finish) - in oil-based paint and then stick the (water-soluble) salt crystals to it, in the desired pattern of paint chipping. After the salt is dry, subsequent overpainting should then be detachable by breaking loose the salt.

My first test of the above used truly "generic" table salt, as shown; the kind with tiny, uniform (if you were to look at them closely) rhomboid crystals, and differed from the original example in that: 1) I did not use a brush to arrange/clump the grains (see below), and 2) I did not use a blow-dryer to dry the salt, but simply allowed it to dry overnight:

I tested out three types of undercoat (top); from left-to-right, respectively: Testors® 1290 Chrome, Pactra® RC262 Indy Silver and Tamiya® TS-17 Gloss Aluminum - all from rattle-spray cans:


Click on Image to EnlargeNote Testors Chrome (leftmost) goes on more "silvery" than the other two, but what the camera does not show - though very prominent to the human eye - is the Pactra Indy Silver (center) goes on by far the brightest - the most like "white metal" - of these three. After drying overnight, all three were uniformly sprayed with water and sprinkled with salt crystals, induced to clump into larger, more irregular masses by repeated spritzing and re-sprinkling; this was likewise allowed to dry overnight.

The lineup was then sprayed uniformly with Testors® 1910 Dark Green (FS 34079) - again, allowed to dry overnight - after which as much of the salt as possible was broken free. I say "as much as possible" because the first (unexpected) observation was that the salt did not want to come free; even after using the stiffest toothbrush available, vigorous buffing using a paper towel was resorted to - already inducing the Pactra Indy Silver undercoat (center) to separate - and in all three tests leaving pitted/bumpy textures embedded in the paint finish; creating an impression more of corrosion than of paint flaking. Of the three, the least "corroded" appearance was retained by the Testors Chrome example (leftmost), and by far the most exhibited by the Tamiya Gloss Aluminum (rightmost).

Suspecting my repeated wetting-and-sprinkling to get larger salt clumps as the cause of the above (undesired) results, I tried again, this time starting off with larger/irregular salt chunks:


Click on Image to EnlargeThis test limited to the Pactra Indy Silver (left at top, and bottom at left) versus the Tamiya Gloss Aluminum - again I've (unsuccessfully) tried to get the camera to show how much brighter is the Pactra - but how much glossier is the Tamiya. In any case, using a sea salt grinder (bottom right), I was able to get nice, irregular coating of salt in just one application - once again allowed to dry overnight.

After spraying a uniform overcoat of Testors Dark Green, I then extended the test to include addition of a second topcoat color; a brown consisting of a mixture of Testors® 1955 Afrika Mustard (FS 30266) and 1954 Light Earth (FS 30140):


Click on Image to EnlargeUpon which (top) I discovered the obvious - that masking tape of course will not permit masking a hard line over the jagged salt crystals - and it occurred to me that use of latex masking fluid (2nd from top) might work. Indeed it did - and to show this new demarcation, I sprayed yet a third coat: Tamiya® TS-15 Blue.

The result (bottom and 2nd from bottom): the latex masking (of the blue stripe) was 100% successful - notwithstanding the very same "corroded" textures from the chipping - again, the salt bonded into the paints - as well as some separation of the Pactra Indy Silver base coat. At bottom, closeups of both the Pactra (left) and Tamiya (right) examples show the appearances as clearly as possible.

I concluded that neither of the above variations on the "salt-chipping" technique is acceptable for my current application - nor, indeed for 99% of all aircraft "weathering" - however it appears very promising for depicting substantial corrosion such as along waterlines (along with barnacles, etc.) on ships, or especially for depictions of wrecks.

If anyone(s) knows any other variations on this technique(s) involving salt - or what I may have done "wrong", in producing the above results - please don't hesitate to sing out!

Cheers,

-Matty