effective weathering for radiator grilles?



i have a question for you weathering folks out there. how do you make the "sooty/darkened" appearnce not so new engines have. painting the radiator grilles all black and erasing with a pencil eraser to show the ridges is unrealistic and frankly tacky ( i know as i have 7 year old engines i did basic so called "weathering" on the radiator grilles and it sucks but i was 14 so :p ).

i am doing light weather jobs for some SF c40-8w's as if they were running right prior to the bnsf merger, ie, kept mostly clean. i have tried dry brushing the grilles black, it is semi effective, but does not reach the grooves properly as intended in most places. how would you get the effect drybrushing has (semi darkened but not too tackily dark) into the grooves of the grilles? (see attachment)

any advice on how to make weathering in the grilles like this would be greatly appreaciated as it will help me hone my so far weak weathing skills
There are many techniques and I've found that different approaches work better on different colors. On Santa Fe Super Fleet models, I like to use ground chalk for grilles. A 50/50 mixture of black and rusty brown will give you a dirty shadow color, which is basically what you're looking at when you see these grilles. Use clear tape to mask around the frames of the grilles and apply the chalk with a boar's hair brush.

Sometimes, depending on how smooth the finish is, the chalk simply won't stick. In that case, you might want to apply the chalk as a liquid by dissolving the ground chalk mixture in water, alcohol (70% IPA) or mineral spirits, but if you go with the liquid, do not mask the area off. The liquid will migrate outside of the grille area and creep under the edges of the tape by capillary action.

Paint is certainly an option as well, and if you're comfortable working with them, artists oils are a great way to go. The pigments are ground really fine and it's easy to thin them into a wash. The key with oil paints is layers, layers, and more layers. Oil paints lend themselves well to the blue and yellow Santa Fe diesels, especially the faded ones. Still, the pure flat of chalk on top of oil in the grilles can be very effective.

Masking the model to weather the grilles is a must if you're going to weather with an airbrush. A thinned mixture (not quite a wash) of the black-brown mix sprayed with a low paint to air ratio will yield a very flat finish that dries practically on contact. Complete coverage isn't necessary on the first pass. Just hit it enough that you've discolored the grilles. Once you remove the masking the too subtle effect you got with the airbrush is often very effective against the unweathered body.

There's really no best way. I have my favorite techniques for Super Fleet locomotives, but they may not work for everyone. So, just give any of these techniques a try and see what works for you.
wow! that was a wealth of information thanks a bunch, one last question, where can you buy these chalks? can you get them at most art supply stores like hobby lobby, or are they more at model railroad stores? i have also had some success with oil pastels with weathering and may use that as a possible alternate to chalks, but nontheless would like to know where i can buy they chalks at :)
I think you hit the nail on the head, there Bill. I got mine at Hobby Lobby. They are artist's chalks, maybe a 12 color set. I chose the earth tone color band, so I have several shades of iron oxide, yellows and black. I recently used up a gray set that went from white to black. That set was very useful for toning down the colors I mix up from the earth tone set.

You can get special "weathering chalks" and many people love them. There are also weathering powders, which are apparently ground pigments that have the ability to "grab" the surface better than chalks. The upside is they don't rub off. The downside is they don't come off! I make too many mistakes to commit to the weathering powders, so I stick with oils (they take hours to dry and can be easily wiped off when I make a mistake) and chalks. I was an art student in college, so I've been around these media for several years. In fact, I have used the same set of chalks for five years (and it was a replacement of the same set from before). I figured I already had the supplies, and I'm plenty comfortable with them, so I've never bothered changing.
My technique was to use very, very thin washes of latex thined with isopropyl alcohol. the alcohol gets it to "wet" in the tiny grooves. As it evaporates, the paint is left heavier in deeper areas and not at all on the raised areas such as grill mesh. It can take several applications but since it is built-up and not all at once, you can sneak up on the right amount.
Hi Ken what ratio of latex paint to alcohol do you use? It sounds like an easy way for me to do it. :D
Cheers Willis
I never measured it, Willis, but I would estimate it was perhaps 1 part paint to 5 or more parts of alcohol. It needs to act more like alcohol than paint as far as how thin/thick it is, if that helps.

more dilute is better as it works best when done a little at a time.
Thank's Ken, I'll put that in my notes. The next one to be painted will be a BN green GP9 so I'll try it on that one. Most of my units are black but a few will be lighter colors.
Cheers Willis