urethane wave/lump whatever you want to call it ?

[440A-body]

OK so I have been painting and doing bodywork for over 25 years as a hobby, and one thing that just chaps my butt is that lumpy look to a high solids clear even after it has been cut and buffed. How does a guy get rid of it? I have tried various clears and found that they all have some to various degree of that tell tale urethane wave or lumpiness to them. I have tried smaller tips, higher air pressure, and even over reducing it. I have used high end and cheap stuff, same with the gun from an Astro to an Iwata. I have used high solids and mid's. What am I doing wrong? What can I do to fix it and does SPI have something in their line that will provide good UV protection, and NOT have the lump/wave to it.

I have used the Universal clear on a couple of VERY small projects, one being my wife's bumpercover on her car, but it is white and I didn't bother to cut and buff. The other was a silver lift gate for some sort of SUV that I touched up for my neighbor, a spot about the size of a soft ball when I finished.

 

[Barry]

Urethane wave is one thing and one thing only, SOLIDS.
As a painter using high solids all you can to is try to spray a more uniform coat BUT using a 1.3 over reducing will only solve the problem by reducing the thickness of the clear and that defeats the purpose of high solids.
NOW if you are just doing two coat insurance jobs, urethane wave should never be an issue unless there is an application issue.

Now to get ride of it, you wet sand with 400-800 as a 1000 will not remove.
so, if you sanded with 800, then you re-sand with 1500 and buff.
or what i did last was wet sand with 600, then either 1000 or 1200 and then 1500 and buffed.
I stop at 1500, and some people carry out further but at this point just do your normal way.

 

[440A-body]

Urethane wave is one thing and one thing only, SOLIDS.
As a painter using high solids all you can to is try to spray a more uniform coat BUT using a 1.3 over reducing will only solve the problem by reducing the thickness of the clear and that defeats the purpose of high solids.
NOW if you are just doing two coat insurance jobs, urethane wave should never be an issue unless there is an application issue.

Now to get ride of it, you wet sand with 400-800 as a 1000 will not remove.
so, if you sanded with 800, then you re-sand with 1500 and buff.
or what i did last was wet sand with 600, then either 1000 or 1200 and then 1500 and buffed.
I stop at 1500, and some people carry out further but at this point just do your normal way.

Thanks Barry I always know you will give me the straight answer. I will try that on my next project that is nearing the paint stage soon. Also is the intercoat avaliable in quarts? For what I am doing I do not need a gallon.