When I use polyurethane satin varnish on my aircraft models it seems to make the base coat color darker. I am working on a 1/16 A20 Havoc in USAAF Olive Drab and the varnish looks as though it darkens the OD, is this true or am I mistaken ? If it is true how do I retain the original color shade and use the varnish ? Thank you for any advice. Rob
You are not seeing things. Gloss tends to deepen / darken colours versus the same shade with flat. I can’t remember what the phenomenon is called, but it does happen.
As to keeping the same shade you want, the first thing to know is why you are putting the gloss on in the first place. If you are doing it to seal and protect, then just go over the gloss again with a flat coat and the shade will lighten up again. If your goal is to have a semi or gloss finish, then you have more work ahead by trial and error to find a lighter initial shade that when it darkens due to the gloss, it is the colour you want. I don’t know of any way to tell how much a colour changes when gloss is applied, so testing is your way forward.
Hope this helps a bit.
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Yes, it’s an optic phenomenon indeed.
Gloss makes colors richer, deeper, more saturated, more contrasted, kind of “wet”. Matte has the opposite effect : colors looks more muted, more dull, less contrasted.
I’m not sure of why but high roughness scatters lights more, adding virtually a new layer over the paintjob. Gloss meanwhile focuses the light instead of spreading it on the surface. I’d hazard the guess that gloss actually reveal the “true” color underneath… But you have all those reflections that look out of place. It’s more or less the same difference between wet, fresh paint vs dried paint 24h later, I suppose.
here you can already see with a simple CG setup how the green and brown colors look different when matte ( left, high roughness ) vs glossy ( right, low roughness )
Unless you’re a genius or have a lot of experience ( and even then… ) it’s hard to predict exactly how a color will look like under gloss, satin, or matte. The only sure way is the plastic spoon test. Spray your primer on a few plastic spoon, spray your test colors, spray your clear. Takes time though : you have to wait for each layer to cure.
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Great responses thank you. I wish to apply local oil washes along panel lines and rivets, and as far as I know one needs to apply a varnish beneath it. Now must you a satin,or gloss varnish to help achieve this technique or can you use simply a matt varnish to apply oil washes ? Thank you
The varnish type greatly impact how enamels and oils will flow !
The glossier ( smoother ) the coat, the more it will flow. As you go toward matte, the roughness of the surface will prevent the liquid from flowing and it will start staining in place instead.
For pinwash, where you apply some oil or enamel to the relief, you want capillary action to work without obstructions, so you want gloss. Matte will immediately stop the flow. Not to mention, a rough surface will be harder to clean so you end up staining your plane. You can get results with Satin, but gloss will be better. There is the Sludge technique where you happily cover your model with a lot of wash and rub afterwards, but I’ve never tried it and I’m not sure what kind of coat it calls for.
AFAIK, a common workflow is like this :
- You assemble, paint, gloss coat, decal, re-gloss ( locally ) over the decal to protect them.
- You do your panel wash relying on capillary action to fill the seams or run around the relief. you wait a bit, you clean the excess with a super mega uber thinner-damp cotton bud or kitchen paper.
- You put on satin and you do the actual weathering. Filter, dots, highlights, modulations, dirt, exhaust soot, etc. Satin is a bit more forgiving than matte, hence why it’s commonly used at this step.
- If you want, you can, in the end, do your actual final coat, satin, matte, or even gloss to protect your work and unify the sheen.
- ( I’m not sure, yet, where you can slide the pigment step for mud, earth, soil etc on wheels, tracks, undercarriage… )
I’ve seen some very nice videos describing the pros and cons of all clear type, I’ll see if I can find it again when I’m back home in a few hours.
disclaimer : I’m still learning, so I hope I’m not making wrong claims 
Thank you so much this helps, I am new to this as well. In regards to ensuring correct color match, I will lighten the original color first. This way I can try to ensure the color does not darken too much after the varnish applications. Would anyone know off hand what colors one can use to lighten Olive Drab ? Thank you
Ah! Found it ! Timecode 5:50, he goes over the effect the clear types have on wash.
The video is actually quite informative, I’d recommend watching it entirely. Covers the base!
As for your latest questions, I’m not sure, I must confess. Maybe Khaki ? Or just a bit of white. It also helps with scale.
What is the actual product you’re using? That sounds more like a product for woodworking than for stain- or matte-coating a model.
Apologies for the delay in replying. I am using Vallejo products. Satin poly varnish. Thank you
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Thanks, George! When I saw “satin polyurethane varnish”, I thought of a Minwax product for woodworking.