I've been searching for some answers to an odd phnomenon I noticed a week or so ago!! I did very thin wash with thinner and black, matt Humbrol enamel. When the thinner evaporated I found black specs in the lines and other things I highlighted with the wash??

Any ideas??? This was an enamel wash over a throughly dried and cured Tamiya Red Gloss...

My Humbrol paints are 6+ years old from when I bought them. Maybe 1 yr on shelf before I bought them...

I have 10+ years humbrols on shelf ,some of them have no problems but some have the same problem as yours.i think every opening of the box takes a while from the life of paint.as more you open to use,life goes shorter.

I had some Humbrols that lasted nearly twenty years. Opening and closing pplays into the life span as the thinning agent evaporates when it's exposed to the air, even in minute amounts, leaving a greater concentraton of the pigment in the container.

and i forgot to say paint bottles must be stored upside down after the first use

Interesting concept Graywolf, but might I ask why?? Do you mean like Model Master's bottles or the tins that Humbrol comes in - or all of the above??

all above..when upside down them,paint goes down and thinner goes up...less thinner evaporation=longer life of paint