Rough/dusty finish when Testors Clear Lacquers airbrushed

True enough Ross.

All varnish coats will darken, though flat coats darken less as it scatters the light more. I have paper swatches that show unvarnished, gloss varnished and dull varnished sample that show this quite clearly, but they just don't work on the internet! And they can't fix a problem with the actual printing or paint job, no matter how much we wish they would! 

You're welcome!

Lacquer thinners are blends of various solvents, generally of fast evaporating types. Toluene and xylene are slower movers. You can also try adding a small amount of mineral spirits as a cosolvent, probably on the order of 1/8 of your total reducer (thinner) volume (a few drops in your paint cup or bottle.) Too much and your coat will run.

As for the retarder, you might find it at a craft or artist's supply store, but your best bet is a store that caters to professional painters. Make sure you don't get an acrylic retarder!

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Bill's description of gloss vs. flat and the effect on color is essentially correct. However, the darkening effect also occurs with a properly applied flat, it's just less noticeable. Also, applying a flat over the gloss will not completely lighten the color to its original apparent shade, especially if the paint's surface texture was exceptionally rough from being applied too dry.

 

Clear coats or varnishes tend to darken dark colors. I'm sure there's a scientific word for it. It's the same result you get when you wet unvarnished wood, it's why it highlights the grain. The dark colors get even darker, while the light colors stay the same. I see the same thing on the printing press when using varnish as an overprint. It's also why your car looks better wet.

I think it's because the varnish (or water) smooths out the surface which scatters the light reflected off the paint. When we view color with are actually seeing the light reflecting off the surface. Gloss reflects MORE light, therefore MORE color (I'm probably explaining it wrong). The matte coat should bring it back to "normal" but it all depends on how much flat base is added to the varnish.  Less gives you satin, more gives you dead flat, too much gives you chalky white! Note that ALL matte coats are nothing more than clear gloss with flattening agents added to the mix, even pre-made ones. Improper mixing will give you varying results. It's why you sometimes see posts from people saying they applied such and such matte coat and it's still shiny. 

Triarius wrote:

Your dusty finish is because the paint is drying slightly before it gets to the model surface. Lacquers are particularly susceptible to this, especially in dry conditions. Try increasing your dilution ratio to 4 to 1, drop your air pressure, and stay within 3 inches of the surface. Or you could try adding a retarder. What are you using for thinning? A slower evaporating solvent might help, too. I've never heard of a problem like that with Future. I'd need more information to diagnose it. Be aware that any gloss coat applied over a flat will make the flat appear darker, especially if the flat was applied a little dry, as I suspect might have been the case.

 All great tips and I thank you for them. I use a hardware store "Lacquer Thinner High Strength" as I can't imagine using anything else with this type of lacquer. There are other types of thinners at the store (Acetone, Toluene) but I understand they are even more violatile and faster evaporating. What type of retarder are you refering to?

Your dusty finish is because the paint is drying slightly before it gets to the model surface. Lacquers are particularly susceptible to this, especially in dry conditions. Try increasing your dilution ratio to 4 to 1, drop your air pressure, and stay within 3 inches of the surface. Or you could try adding a retarder.

What are you using for thinning? A slower evaporating solvent might help, too.

I've never heard of a problem like that with Future. I'd need more information to diagnose it.

Be aware that any gloss coat applied over a flat will make the flat appear darker, especially if the flat was applied a little dry, as I suspect might have been the case. 

Another way to get rid of that dust is to LIGHTLY scour it with a worn out Scotchbrite pad.  Also helps polish the surface a bit!

Here's a new twist...I took a toothbrush and scrubbed the spot where the "dust" had collected. It came off and disappeared...Strange.

I have had similar experiences with lacquers and Future.  I have had the rough textures spraying Gunze Mr. Surfacer, and problems with cracking and runs with the Future.  Sorry I have no answers for you, but I'll be watching this thread hoping someone can give you some insight!