Solvent based washes over Acrylics?


G

GMTrainNut

Member
Hey all! Another question on my journey to custom painting nirvana..

I've switched over to water based paints, Pollyscale for the most part. I had some initial issues (see recent thread about surface prep) but am past that and have come across my next obstacle.

I like to add depth to grills on locos by using a dilute wash. In the past that wash was usually Floquil solvent based, and was used over a shell that was painted in a solvent paint.

I did some experiments with a water based wash, and the results were less than stellar. I first tried a wash using distilled water with a few drops of dish soap. The soap failed to break up the surface tension of the water enough and the results were splotchy looking.

I then tried another mix using an acrylic flow enhancer, sold in art supply stores (I believe the brand was Liquitex). The results were okay but still did not behave as well as the solvent based washes.

So I've thought about the next move and here's what I've come up with:

1) A wash using strictly 91 percent alcohol and paint. My fear with this is that the alcohol will cause fading like it does with Testors Dullcote. I'm not sure that the same "whitening" effect would happen with water based clear coats from Pollyscale or Model Master, and maybe I have to do yet another experiment to determine this.

2) Go back to a solvent based wash, but give the water based undercoating enough time to dry so that the solvent doesn't attack the paint.
I've read about folks using solvent based paint or clear coats over water based paints, but that seems dicey. How long would you have to let the undercoat dry before safely applying a solvent based wash?

3) Mask and paint the grill areas with the gray/brown mix, then dry brush the body color on the raised grills.
I've done this, but it's never been my favorite method, no matter how careful I've been it tends to come out uneven looking.

As always many thanks in advance for any advice, input, etc!
 
If you dullcoat the model first, you should be able to use solvent based washes, which you'd then seal with another coat of dullcoat. Another option for general weathering is india ink heavily thinned with isopropyl alcohol. My preferred method is using weathering chalks since you have no worries about causing problems with the paint and it's easy to clean off if you go a little too wild. :)
 
Don't use Isopropyl ANYWHERE on top of Dullcote, you'll receive major fogging... Most of it is correctable with more dullcote, but not always.
 
Thanks for the responses! Since I have a couple of spare body shells on hand I'll do some experimenting.

How long would you wait after painting a shell with water based paints to apply dullcote (Testors)?

Josh,

I am familiar with the effects of alcohol on dullcote, learned that lesson the hard way years ago! But have you seen the same thing happen with the water based finishes like Pollyscale or Model Master?

Again, thanks for the responses!
 
Use the smell test. If you can still smell any paint odor when you put your nose on the model, it needs to dry some more. Drying time is really variable depending on the brand of paint, how thick it was applied, temperature, humidity and, I think, sometimes, the current sun spot cycle. :)

I've used alcohol/india ink washes on models painted with waterbased paint without a problem. As Josh said, don't use it if you've already applied dullcote. I was only advising dullcote if you are going to be using solvent based paint washes exclusively.
 
Jim,

Thanks for the response. I did one experiment today, I dullcoated a test shell that was painted with Pollyscale about 10 days ago. So far it looks good, no sign of any weird reaction.
 
I've never had any problems really with paint reactions, other then the occasional pealing paint when it dies not stick to the underlying paint.
 
This past weekend, I was doing the exact same thing - applying a wash over grills to achieve depth. The first try was Poly Scale with isopropyl as the thinner. The alcohol caused the paint to congeal and instead of a solution, I had flakes of paint floating in the isopropyl. Tried several bottles and the result was still the same.

Finally reverted to water as the agent and all was well.
 
Sorry to dredge up an old topic...

But I'm still having issues. I've been trying to stick with Pollyscale for everything, so for now I've shelved the idea of using solvent based paints for grille washes.

But everything I've tried still results in a whitening effect when the wash dries. The shells are painted in Pollyscale, then, after decaling, are sprayed with Model Master flat finish. After letting that dry about a week, I started experimenting with washes of Grimy Black using the following:

Testors Universal Acrylic thinner
Isopropyl alcohol
Denatured alcohol
Windex
Distilled water
Distilled water with a couple of drops of dishwashing detergent
Distilled water with Liquitex acrylic flow enhancer

All of them, when dried completely, display a whitening effect.

This test was fortunately done on spare shells. But in order to complete a couple of projects I resorted to masking and painting the grilles grimy black, then drybrushing the body color over the grilles. That works okay but I would really prefer to use a wash.

Any thoughts?

I'll post a pic or two later of the results I am seeing...

Thanks in advance.
 
When you use Isopropyl for a thinning agent or wash, use 70%, not the 90%. We use 90% for fading and stripping.

You already know this.....never use Isopropyl after Dull-Cote... If you do, no biggie, just hit it with Dull-Cote again.

I always mask off intake grills and spray them with whatever color/colors I'm using for that particular engine. Intake grills are more solid in color than I can get with a wash. I have also brushed the intake grills as well, although I work with 1/48 scale. Several years ago I did HO but always just mask and spray for grills.

After spraying Dull-Cote at a 50/50 mixture with Laquer Thinner, I can handle the shell within 10 minutes. My weathering projects usually have 3-4 different layers of dull-cote at different phases of the project.

Although I have tried Poly Scale and other water based paints, I always say I will NEVER do that again. I stick with Floquil, sometimes Scalecoat II. Water based paints just have too many problems when thinning is required.

I do use artist acrylics for weathering, thinned down with 70% isopropyl.
 
You could try a different barrier between the acrylics and solvent-based paints: Future floor polish. It's impervious to solvents and it airbrushes nicely without any thinning. Yes, you'll have a glossy model after applying the Future, but once your weathering is complete, you can always spray a final coat of dullcote.
 
You can't apply chalks or weathering powders to a glossy surface, it has no grip. The powder will just fall out without sticking. If you do your weathering with an airbrush, not a problem.... but the powders/chalks need a flat finish to adhere to.
 
Thanks for the responses! Yes, I have been very tempted to go back to good old Floquil, Scalecoat, etc.

I agree that sometimes it is best to just paint the entire grille, radiator, etc the desired color and be done with it. But there are some cases where the body color really does stand out in front of the "grime" color behind it.

Here is an example of the chalky white effect I keep getting:

uboatgrilles.png


I will probably go ahead and mask and paint the grilles, not too much fun on a U-boat with 14 per unit!

BTW nice SF unit there Laidoffsick!
 
Laidoffsick said:
You can't apply chalks or weathering powders to a glossy surface, it has no grip. The powder will just fall out without sticking. If you do your weathering with an airbrush, not a problem.... but the powders/chalks need a flat finish to adhere to.
Click to expand...
That may be true (I don't use powders), but there's nothing preventing you from putting dullcote over the top of the Future. The Future simply acts as an impervious barrier to solvents. Once the paint underneath is sealed with future, you can apply solvent washes over the top without damaging the paint underneath.
 
Ryan,

I've been curious about the Future Floor Polish, having read about it in numerous places...sounds like enough reason to try one more experiment.

Thanks!
 
GM, try getting some extra fine point paint pens in black and brown. Sometimes the vents/grilles look better with just black or with black first and then another coat of the brown over it to make it less dark. It's much easier than masking and you can paint just the grill area, leaving the body color intact on a newer unit. The grilles on these two units were done with paint pens:

CSCU30CatFirstAveMedium.jpg
 
GM Train - I had similar results to those in your photo. I simply applied a second coat and made sure the solution was not minimized by spreading it too thin. Worked well. And depending on the solution percentage, a little dirty film on the framing is normal. If it were too heavy, I dry brushed some frame color.
 
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