after reading (3) pages of search results, I still couldn't find an answer to my question.

when i'm caught without the correct color in the MA line, and have to jump into MC paints, I understand how to get it thinner in order to airbrush it.

Q: how long does thinned paint maintain its covering & drying properties?

I have some 5 year old paints, and I would be happy to thin the whole bottle if it wouldn't compromise the qualities or reduce its shelf life to 10 days.

thanks

Thinning the paint will shorten its shelf life. Best to thin what you will use in a reasonable time. How much shorter the shelf life depends on the type of paint and the thinner to paint ratio.

Here is my 2c/Tuppence H'apenny worth...

Vallejo ModelAir, needs thorough shaking/mixing, I put a few 3mm stainless steel nuts/BB's in it.

I also use a little of their Airbrush 71.161 THINNER, AND 71.262 Airbrush Flow Improver & sometimes 597 Retardante/slow dry.

With ModelColor (MC) the above thinner/flow improver/slow dry are essential, for air or brush painting, but their original 061 diluyente/thinner is intended only for brush painting.

Please be aware that MC will colour shift lighter when thinned well enough for spraying and both MC and MA are prone to tip dry.
Good luck.

thanks for the guidance (both replies). "it's a process".

That it is...
although I've gone back to using Tamiya acrylic with X20a thinner, and MIG's for ease of use as they are a lot more forgiving of my kack-handed efforts.

I've recently discovered and used Model Color. It's all via the AB.

I'm in Arizona... Things are often DRY here. Any paint thru an AB is going to challenge the tip-dry deities.

I thin the MC generously (around 2:1 or even 3:1 or a bit more) with generic blue galss-cleaner (generic "Windex") which contains ammonia plus a wetting agent. In general, I shoot the mix around 15 psi over a 0.35 to 0.5 needle for almost every use from broad coverage to under 1/8 lines. Back off the psi some for the finer work - down to maybe 10 psi.

Some suggest adding a flow-enhancer and / or a retarder. The blue glass cleaner stuff serves as a sort of combo. I am going to try adding some "Liquitex" to my usual thinned mixtures to explore the flow-enhancer effects.

Tip-dry happens. Unless you really "up" the local humidity, you will eventually suffer the drying while you work. I've taken to keeping tiny bristle-brushes ("micro-brushes") on hand to brush clumps off the needle. Shooting with lower psi helps hold this back. I have also used a wet "scrubber pad sponge" as a de-clumper dry needle treatment. Just stab the needle into the wet spomge and twist it around a bit to clean off the needle.

Cheers! Bob

interesting video and brings about (of course!) another question:

I've seen ump-teen video & other references where a hair drier is used.

Q: does speeding the drying artificially reduce the paint's bond to the material being painted or previous coat?

thanks

None that I'm aware of

Definitely learned a lot from that video. Thanks!