How to avoid runs?
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Recently I did a job on my car.. It was scratched, nicks and dents on the doors etc..
Got the paint to be butt match and has little blending to do.. The base went in 3.5 coats LS7N Arctic Silver on my Seat Leon.
The base was smooth as silk.. Did all the necessary preparations, dusted the car etc etc..Got my new AirGunsa 1.3 AZ3HTE2 and went to clear the car in a hired booth.
I had added 10% reducer to my clear 2:1 MS Colomix Helios clear, a cheap clear, but buffs to diamond shine..And the problems that I had are major runs/sags on the door panels..
Not that I mind them much, I will sand them down with putty and buff the whole car.. But I really like the finish from my AZ3HTE2.. I got factory finish like NFT5 had said.. The gun performs excellent and It is just what I need for the jobs I have
I was spraying at 29psi wide open, 50%/60% overlap, ~5-7 inches, tried not to lay the clear too much but at the end.. ahh not satisfied for me..
So spray gun buffs there, care to help?
First off, anyone who is trying to do good work will get (some) runs now and then. If you don’t, then you probably aren’t trying hard enough…
Having a gun that is suitable for your product is crucial. Correct tip size, adjustment etc. You need to adapt to the environment. Temperature is a big factor, as is proper reducer selection, and following the proper mix ratio. While some products may respond well to being over reduced a little bit, it is best not to. At least not until you are very familiar with the product. Flash time is a big one, putting your second coat of clear on too soon can be disastrous with most clears. Limit the number if coats to what is recommended (ie: 2 coats of clear).
Follow the tech sheets, make “minor” adjustments as needed to suit you. There is no need to re-invent/ experiment excessively.
Did the runs come in the first coat or the last?
If the former then you were probably trying too hard. I always hold back a little on my first coat. Still flat, wet and shiny but I try not to get it on too heavy. I find I can put subsequent coats on much heavier and they’ll be fine, whereas if I did the same with the first one it’ll just end up dripping on the floor. Maybe it’s the first coat absorbing some of the solvents in later coats helping it to stay put. Who knows? :unsure:
If they appeared in the last coat then I’d suggest you didn’t let the first flash enough. Some areas always take longer to flash than others, particularly if you don’t have a good turbulent airflow around the car. You can see this more easily with base. Some places around body lines or angle changes will take longer to flash than the middle of a flat panel for instance. Watch for these areas as you base and bear them in mind when you move on to clear.
I got the runs on the first coat.. Maybe I hammered it..
First coat runs are as Ben & Andy say. Needs to be wet, but only just. Also note what Ben says about temperature – paint & panel need to be matched. Cold panel = runs, cold paint = runs. The other thing is that it takes a moment for the first coat to flow across the base. You can think that it isn’t wet enough and go for another pass which will then be too much.
Yeah.. that is the thing I did.. on few places on the panels.. it looked a bit thin and I went for a second thinner pass and it was too much then..
I have in total: 8 runs/sags 🙂
So should I sand them down and buff or sand everything and re clear?
[quote=”Ben” post=33236]First off, anyone who is trying to do good work will get (some) runs now and then. If you don’t, then you probably aren’t trying hard enough…[/quote]
:agree Never a truer sentence written! lol
Sanding and polishing isn’t always an option. When I’ve gotten runs, I usually try to salvage first in hopes of polishing, knowing that I might not quite get it or may burn through and need to repaint. Fixing runs can be tricky.
I have fixed some pretty nasty ones and they’ve come out great…some, however, you just have to repaint.
My method is to take a razor blade and place a little masking tape on the ends (so the corners don’t dig in) and use it as a file. I will file the run and surrounding area until visually it is flat, and I can not feel the run anymore. Then I’ll start blocking. Typically 800 dry seems to be a good start to get it going, then move to 1200-1500 wet, then 2000 (blocking each step). The 800 scratches can be tricky to get out, but they will come out. It is important to be careful as you will be removing a lot of material. The step with razoring it flat and then the 800 is cruicual for getting it straight.
There are other methods (Jimmo has a video of the putty method, I think), but none have worked as well for me.
Like Ben says , and when you first go over 2000 grid sandpaper with your razorblade by rubbing it just [b]one [/b]way square to the sand paper , creating a 2000 grid burr on one side of the blade , then slightly bend it to keep the edges out of the paint and carefully rub over the run while holding the blade nice and level and let the 2000grid burr slowely take away the run.
You are done when you see no low spots anymore.
This is how i do it and it is a very effective way.Rob
I have decided to redo the job.. It is much easier for me to kill everything for me with DA and repaint in 1hrs. I have the materials at hand so why not go use them..
Nothing wrong with that. I would still consider flattening the run with a razor and blocking it (starting with a coarser paper and working up to 600-800). Nothing worse than re spraying it and having a little “ghost” of a run.
Good luck, I’m sure it’ll turn out great this time for you!
Jimmo’s putty trick is where it’s at when it comes to removing runs. :weights
I use almost exactly the same method as Ben, usually with great success. I’ve used the putty method in the past too, also works well.
Anyone tried the devilbiss shim mask? It looks like a gimmick to me but I’ve got one coming anyway to see how well it works.
Pumice stones work excellent on runs as well. They take a little longer but they don’t “give” like sandpaper. I’ve got many a run out that way.
What kind of pumice stones? Normal health care / skin care stones ????
I can’t find any specific car pumice stone.. care to explain your technique?
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