Spraying 2K Urethane Primer

Mando

Promoted Users
Hello everyone here at this forum.This is my first post so i hope I don't embarrass myself. I just retired from my job as a electronics technician and have started a project on my 94 chevy truck. It had a few dents and the old paint was fading out.I repaired the small dents with body filler,sanded the filler with 80.180,and 320. I used guide coat to make sure i did not have any high or low spots. After taking care of the dents,I than sanded the complete truck with 400 grit. I made sure that there are no shiny spots on the body at all. Looks pretty smooth now. Now,I am getting ready for primer so here is my question? I am using a 2K urethane primer along with its activator and reducer. Its a 4.1.1 mixture. I have a gun that has a 2.0 tip on it and I also have an extra tip that is 1.4. I am going to use the 2.0 for the primer and 1.4 for base. I hear about spraying medium and wet coats.How is this done? Are this coats accomplished by putting more or less reducer? Can someone please explain this to me. Also,is 2 coats good enough or should I go 3 coats. The primer is a high build primer. After I finish the primer,I want to let it set for a few days before wet sanding with 400. What do you folks think on how I should tackle on this primer job. Oh,the sheet on the primer says to apply 2 full wet coats at 40psi. My gun requires 5 to 6 CFM and my compressor is rated at 6HP at 11.5 CFM so i think I have enough air pressure to do the job. Need some advice and or opinions please. Thanks to all for your help.
Mando
 

texasking

Promoted Users
Sanding high build primer with 400 initially is working yourself harder than you need to. Using 220 to start would be the finest I would start with. It will cut the texture out much quicker and get it straighter, also. After 220, use guide coat and finish with your 400 before sealer. 2 coats of high build should be enough for normal filling, but 3 wouldn't hurt if there is waviness or extensive bodywork. Wet coats should look relatively flat, with no dryspray and just short of runs. Overreduction should not be needed with a 2.0. There will be orange peel, but that is OK.
 

Mando

Promoted Users
Thank you very much for your reply. If I do get orange peel on the primer,will the 400 grit get rid of that or should I use maybe 320 and than 400? Being that I will be using a 2.0 fluid tip,I can spray the primer without using any reducer at all? Won't that cause runs to come up being that its a high build primer. Just wondering.
 

Dave C 5

Member
I would plan on sanding twice- first with 220( will cut quicker) then sand with 400- you’ll work harder and get waves in the primer if you just use 400. If I understand the next question correctly- the answer is too much reducer will cause runs if you’re not careful
 

Mando

Promoted Users
Ok, thank you Dave. I will go ahead and use 220 first and than move on to 400. I have a shop but not a paint booth so what happens if something falls on the panel (like a little bug) while i am spraying the primer.Just leave it alone till after the 2 coats and than correct the problem when sanding.
Just wondering.I hope I don't see a problem but things can happen and thats why I am asking. Thanks again.
 

Dean Jenkins

Promoted Users
Ok, thank you Dave. I will go ahead and use 220 first and than move on to 400. I have a shop but not a paint booth so what happens if something falls on the panel (like a little bug) while i am spraying the primer.Just leave it alone till after the 2 coats and than correct the problem when sanding.
Just wondering.I hope I don't see a problem but things can happen and thats why I am asking. Thanks again.
Lots of us paint in our shops with good results, just need to control dust and have some ventilation to move the overspray out as much as possible.
I've had a bug land on the wet paint while I'm spraying. Really annoying .
My choice was to wick it out with a gloved finger. The crater can be easily fixed, but didn't want it entombed in the paint.
 

Mando

Promoted Users
I sprayed the high build 2K urethane primer yesterday.I shot 2 coats. In a couple of days I am going to start block sanding with 220 and than move on to 400.I will be using guide coat during each stage to make sure panels are straight. The primer looks pretty good but I did get a small imperfection (air hose rubbed on the fender due to rookie mistake)on the driver door that I need to fix. I also have some orange peel on the rear left fender. Question: When working on the driver door,after sanding that area,do I re-prime that area only or the complete door? Also,when sanding with both the 220 and the 400,is it better to wet sand or dry sand? I know wet sanding is a mess but if it gives better results with the base,I'll wet sand.
Thanks everyone.
 

Dean Jenkins

Promoted Users
I sprayed the high build 2K urethane primer yesterday.I shot 2 coats. In a couple of days I am going to start block sanding with 220 and than move on to 400.I will be using guide coat during each stage to make sure panels are straight. The primer looks pretty good but I did get a small imperfection (air hose rubbed on the fender due to rookie mistake)on the driver door that I need to fix. I also have some orange peel on the rear left fender. Question: When working on the driver door,after sanding that area,do I re-prime that area only or the complete door? Also,when sanding with both the 220 and the 400,is it better to wet sand or dry sand? I know wet sanding is a mess but if it gives better results with the base,I'll wet sand.
Thanks everyone.
Some Orange peel is expected on 2K. I would block it out with 220, you may find enough low spots that you'll want to shoot the whole panel again anyway. If not, then just hit the bad spot.
Dry sanding 2K is what I do (wear a dust mask - the pink ones that go on 3M mask are awesome.)
Wet sanding for base/clear.
 

Mando

Promoted Users
Got my 2K primer all sanded down.I started with 220,than,320,400, and after 400 I wet sanded with 600.Looks and feels pretty smooth.
Now,before I spray the base and clear,I have some questions on doing that. I am using the same color that has been there since brand new,its Quasar Light Blue Metallic. Question? Should I wash the truck completely before I use the wax and grease romover or can I just use the wax and grease remover without having to wash the truck? I used a 2.0 tip for primer and I have a 1.4 for the base. I was able to read the data sheet for my color on a website and it says that the mixture ratio is a 2.1. ,no activator,just reducer. Do you guys use acticator on your base? I will be using a medium reducer cause of the nice weather here in AZ,about 75 degrees. Is there anything that I should be carefull with when spraying this metallic paint? Like I mentioned before,this is my first job so taking my time with it. Can I use the same 1.4 tip for my clear or do I have to change it to a different size? Oh, since its a truck, how do you guys reach over to paint the top of the truck. I'm not a tall man,just 5.5". I don't have all the special tools that most of you guys have since I just started doing this.
I guess I can remove the tires and put the truck on jack stands and see if that helps. Need some idea's please.
As always,thank you very much for all your help and support with my project.
 
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texasking

Promoted Users
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Mando

Promoted Users
Thank you both so much for this great help that you are giving me. Thanks texasking for the link on the step stool. Question, After shooting the base and while waiting for the base to flash,do I have to clean the gun or can I just wait the 30 minutes or so after the base and than shoot the clear without having to clean the gun. When spraying the base and clear, What is the recommended distance from the gun to the panels? is 5 to 7 inches a good distance? Can you give me some tips on how to prevent orange peel while spraying this 2. I know that my first paint job won't be great but I would like to do a decent job. I hope it does not happen but what if I have a run while shooting the base or even the clear,how do you guys take care of this problem? Sorry for all the dumb questions but this is the only way I am going to learn. Thank you guys.
 

Dean Jenkins

Promoted Users
Not dumb questions at all! We are all learning.

Here is a link to Barry's gun setting guidelines: https://www.southernpolyurethanes.com/gunadjusting
Great place to start.
Once the gun is setup correctly, then you need to fine tune the distance and speed.
The only way to do this is to practice. If you have an old fender or hood or something to practice on, that is ideal.
If you don't have any car panels to practice on, Home Depot and Lowes have 2'X2' or 2'X4' sheet metal that will work, not expensive.
Paper on the wall is fine to check spray pattern, but not for learning to spray.
Learning on the car you spent many hours prepping may not go well . . .

I would not plan on shooting the Base and Clear on the same day.
As a fellow newbie I have learned to absolutely expect that there will be at least some minor trash and/or runs in the Base.
Very easy to fix on dry Base with 600 wet sand, but next day is the earliest to try.
And, it is possible to sand through the Base when fixing, which is no big deal, it can be touched up.
Better to plan your timeline for these things, IMHO.

For the Clear, same thing, expect to have at least some minor trash and runs. Easily fixed with careful block sanding (opinions seem to range from 600-1200 grit wet sand for this, I've played with grits in that range, coarser works faster, but it is harder to get the scratches out.)
Clear needs to really dry and release solvents before attempting to repair trash/runs and begin cutting/buffing.
Getting it outside for some UV is critical according to Barry. I think he said "1 hour in the sun is like 10 days in the shop."
Some guys wait at least a week before doing anything with the clear.

Hope all that helps.
 

Mando

Promoted Users
I have a quick question on a imperfection on the hood after sanding primer. Yesterday I was going around the truck checking how all the sanding looked after a final sanding with 600 grit paper. I don't know the correct name for the area but its on the hood.Don't know if its called a body line or an edge or part of a contour or what but right on the top edge,its showing a very small area of metal. Its a tough area to sand so maybe I put to much pressure on that edge while sanding. What can I do about that problem? Will base coat cover it up or do I have to shoot more primer over it.Its only about 1.5 inches long that is showing metal. Thanks for your help and happy Sunday to all.
 
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