How the hell do you stop brushed paint running?!

[3xpendable]

I am in the process of painting the fuel tank in my MGB after scraping it down, and today a problem reared its head that I've had in the past and is really beginning to p*ss me off!

Basically, whenever I brush paint something, no matter how careful I am, the paint always leaves runs. Its gotten to the point where I'm only painting upward facing surfaces and for example, when I left one part of my tank laid at a very shallow angle (15 degrees tops), I came into the garage today to find some wavy runs on it and its getting me down. I'm using a hammerite style paint and bearing in mind its cold its quite viscous. I put it on as thinly as I can to cover the area and continually check it and brush out any niggles I find while its wet. I don't see how I can use any less paint so do people have a trick? Let me know if so, as the mood I'm in today I feel like not bothering trying to make anything on it look nice anymore.

[tractorman]

I suspect part of the problem is lack of heat. If it is too cold, the paint takes a lot longer to dry, giving it plenty of time to form sags and runs. I would never paint in winter unless I had some serious heating to decrease the humidity and make the room and panel warm enough for the paint to go off quickly.

Thinning the paint helps a little - not too thin, but enough to stop it being like treacle. Then paint VERY thin coats.

Others may have better suggestions, but that's what I do! The last time I sprayed in winter time (it was Christmas Eve about ten years ago), I had a terrible finish: no gloss and sags with enamel paint. I had used a heater to warm the garage, but I should have used two or three heaters, set them going the night before painting and left them on for a day afterwards. I had to repaint the stuff the summer before last (the wet summer!) and made a much better job of it.

[jimmyybob]

Perhaps your doing it too thin.
Also a cheap brush will ruin any good paint.

[3xpendable]

Thats interesting, thanks guys. Fyi I have been using a cheap brush so o might invest in a decent one and a heater!

[mach1rob]

A bit of heat should help. I spent a while sorting a couple of areas under the bonnet today that needed a touch more paint, so far so good, but it's not been that cold down here.