Rough dusty finish with Tamiya paints

[Mark_1984]

I have a problem whereby when I spray mat Tamiya paints into a recessed area, like a wheel well or inside a cockpit, I get a rough finish. However, same paint sprayed onto a flat surface goes on fine. 

 

What at am I doing wrong ?

[Gorby]

The only time I have had this happen with Tamiya acrylic paint is when I have sprayed too far away from the surface. The paint is partly dry before it hits the surface and produces tiny lumps. I don't know if atmospheric conditions could be contributing to the problem. What pressure are you spraying at?   

[Mark_1984]

Not sure of the actual pressure, but it was quite high to get a good flow of paint. 15 -20 perhaps ?

[Gorby]

That doesn't sound too high. I tend to spray at a little lower at about 10-15, but I can't see the pressure you are using being the problem. 

Hopefully someone more knowledgeable than me will be able to give you some advice.

[John Laidlaw]

Yup, too high a pressure/not sufficiently thinned. I've had the same where at a wing joint or other constricted area (and spraying too close for the pressure I'd set), the atomised paint swirls and almost dries before hitting and sticking. Ends up like sandpaper.

 

What worked for me was thinning the paint more - a minimum of 50/50 - and using Mr. Color Leveling Thinner. This means there's a lot more thinner to evaporate before the paint can dry, and the thinner itself has a retarder, allowing the paint to level before drying. The only downside is the smell of the thinner, which requires a proper extractor and, really, a VOC facemask.

 

If you can't use MCLT, Tamiya X-20A will work, but evaporates more quickly. Start at 50/50 and lower the air pressure accordingly.

 

Another trick is to add 10-20% of Tamiya X-22 Gloss Clear to the paint before thinning. This slows down drying, giving it time to level out, and also gives it a nice, tough, satin finish.

 

Good luck!

 

 

[Mark_1984]

Thanks very much John. I'd only diluted about 40% thinners X20A, so more thinners and lower pressure.