I'm still new to using filters and have been trying to apply filter techniques on a Tamiya T34/85 I've been working on for the past week, but things haven't been going so well... please bear with the long post:

My base color was a nice shade of Tamiya Dark Green. After applying decals, I opted to use the dot filtering method, using W&N Yellow Ochre oil paint and AK Odorless Turpentine thinner - I was going for brighter color variation on certain parts of the tank. I began to stump/mix the dots, and things were looking pretty good... until the thinner dried. What resulted was a dusty/milky looking mess. You could see some of the yellow ochre, but a lot of dusty white stuff appeared too, which totally ruined the rich dark green base coat. I know tanks don't usually have vivid colors, but the green was just lifeless. Why did this happen? Was too much or too litte paint or thinner used? I tried to make the brush as damp as possible.

Shortly after that disaster and still feeling adventurous (how could things look worse...?), I tried applying a Sin Industries "Gray for Light Green" filter (it says "gray", but the filter itself is a tan color) for the first time and ended up with a similar result. It wasn't as bad looking as the ochre dot filter, but still a very washed out/dusty looking mess. The filter didn't enrich any color, it just kinda... dried and left dusty, yellow/white residue over the base coat.

Anyone have any ideas as to why this is happening? I should mention that I before this project, I've once before applied dark umber filters on a light khaki-colored Japanese Kurogane scout car, and was actually pretty pleased with the result. The khaki was darkened and the color was enriched well enough... this T34, though... yeah, no luck. Any help or input would be appreciated, thanks very much.

Interesting that you used turpentine. I used it once, it turned to a thick milky mess in the plastic palette. I concluded at the time that it had melted the white plastic palette. I've been using white spirit since with no problems.

Andy

I concur with Andy.

I use ordinary mineral spirits (common hardware store odorless paint thinner) with no problems either with oil-dot modulation or pin / general washes.

The only artist oil paint color that I've ever noticed leaving a "whitish" residue is "Payne's Gray." Because it's a gray mixture, it does have some white pigment in it that can separate from the darker pigments when made into a wash or used for color modulation. It's especially noticeable on dark base colors - like OD or dark green. Payne's Gray can make nice effects when used as a wash on metallic silvers and grays (small arms and other mechanical components).

At any rate, I've never noticed any such effects with other oil paint colors, so I agree and suggest trying mineral spirits next time.

The yellow ocher oil paint dots should have made the underlying green quite a bit "paler" and somewhat brighter in the areas where you used it.

Did you use any general washes or other weathering before you did the oil dot modulation (or other oil color dots before the yellow ocher)? If so, it's possible that the AK thinners picked up some of those colors which created the whitish stains.

Thanks guys. The AK turpentine is supposedly a milder thinner than white mineral spirits, so I wanted to try it out here. The oil ochre modulation was done on top of a satin clear varnish with no filters done before it.

I do have some Klean Strip odorless mineral spirits on hand, so I think I'll retry the ochre modulation with it later today on areas of the tank I haven't attempted to filter yet. Will report back.

I'm no expert however I am in the process of adding filters to a model and the advice on Mig or Ak (I've got confused which one as I bought filters and washes from both) website recommended a Matt surface for the filters and a gloss/ satin for the washes.... Maybe this may be causing your problem?

It may have to do with the thinner you uesd reacting with the varnish you sealed the model with. you should check to make sure you are not affecting the clear coat.

from a post on the finescale modeler site:
"Almost certainly [OK to] use mineral spirits to make the wash [over lacquer clear coat]. I'd avoid turpentine or turpenoid, as these may contain alcohol. If the lacquer is alcohol soluble either of those will attack it."

by varnish, I am assuming you mean a lacquer finish, but if not, it still could be some product in the turpentine affecting the varnish.

the up-shot is, you *might* be able to fix the problem with another layer of lacquer clear coat if the base layer is not TOO badly damaged.