rebells_McLaren

First of all. Please excuse my poor English. Since I was so lucky to be born in Norway, my Norwegian is exellent, but my English is not as good as it should be .

I have just finished putting on Latex paint on the lower wing of my DR1. I put on a clear top coat on the underside using a brush. The first coat went very well, but on the second I noticed some small areas starting to look a bit yellow/darker. I suppose it is because the paint was added to thick on these areas. So I decided to use my spraygun for the topcoat on the other side of the wing. The same gun as I used for the latex paint.
With a very bad result. It seems that it is covered with tiny white dots on top of the coat. No as the coat is starting to dry I can remove some of them with just brushing light over it with my hand. I am starting to suspect that I have put the water/oil filter on the airhose the wrong way ??
Have anyone else experienced this ? The top coat I`m using is a water based poryuthan paint. I know it can be used on the Latex paint so it shouldn`t be clearcoat itself that causes this.

I guess I will have to wait until it is fully cured before snading it down a bit before trying again. Should I use wet or dry sanding ?

Trond.

TomCrump

Let me start out by saying that your English is better than my Norwegian. It sounds to me that you do have a water and oil mixture problem. It could be the the latex wasn't completly dry,or like you said oil from your air system. Try a test panel. Use an air hose that hasn'thad an oiler hooked to it. Of course,disconnect your oiler. Sprayit out and see if this helps. Good luck.

Steve Collins

My Feedback: (8)

Sounds more to me like the clearcoat went on the surface already partially dry. I expereinced something very similar to this while spraying a polyurethane clear. Because the clearcoat/air mixture wasn't right, the clearcoat had already partially dried by the time it hit the surface. To be more exact, it appeared that the usual overspray was too dry and left little geitty feeling deposits on the clearcoat. Some of it could be wiped off but not all. Made a pretty bad mess.

I think either your air pressure was too high or the gun wasn't "pulling" enough of the clearcoat for the amount of air passing through the gun.

rebells_McLaren

I will try to check out how the water/oilfilter should sit on the hose. I tried to open up the needle so more paint would come out, without getting any big differences in the amount coming out.
I noticed the tip of the gun had some small particles around the needle hole. It could be the paint starting to drie out. I noticed that the top coat was almost dry after i sprayed it on. I also used more paint than I did when brushing it on, without making a smooth finish. The coat looks like skin that should have been shaved 2 days ago . Maybe I should try to use more airpressure. I`m using about 28 psi.
I have to ask again. Should I wet or dry sand the clearcoat ?

Trond.

TomCrump

My limited experience says to wet sand with 400 grit or higher sandpaper. Somebody with more experience might have more ideas. Just try a small area and see what happens.

ProfLooney

You Might want to look on nelson Hobby site http://www.nelsonhobby.com/ or email him he has if I remember correctly a retarder you can mix with your latex paint to slow down the drying time which helps a lot when spraying. Maybe he can give you some ideas and you could then find something similar locally. it sounds to me like it is drying too fast as observed from your dry splatter around the tip and needle.

Joe

TomCrump

I was wondering if you can thin the clearcoat a little? Maybe that would help. Try it on a test piece and see if it works.