universal clear die back

danp76

danp76

Oldtimer
Hi guys, when spraying I have been getting die back on the Universal, not sure why. It's totally acceptable for customers, but I can notice a loss of gloss. Initially it's like glass, but the next day, I can see it's just not the same. I have tried several different hardener speeds and even waited the next day to apply the clear. In addition I have applied only 2 coats, with a 30 minute window between. I'm in a down draft booth and shop and spray temperature are in the 70's during and after all painting, including overnight, the heat is left on. I've used multiple guns, Iwata, Tekna, Sata and all create the same results. Not a problem for resto work as it's all cut and buffed, but some collision projects, I'd rather not. Ideas? thanks.
 
Either spraying on the heavy side, not turning the fan off after overspray clears?

Try a small amount of 925-4 on the last coat?

I'm at a loss of ideas, and probably wrong on all accounts.....
 
assuming your waiting overnight for all solvents to come out of the base then keep in mind that how smooth the basecoat is sprayed will play a big factor in this. all paint shrinks as it cures and solvents come out of the film. if the base has a texture to it then the clear will shrink into that and you will lose some gloss. generally its not much but enough to notice for sure. just look at the difference between jobs where clear is sprayed over sanded clear vs over basecoat.
 
Jim what you are saying makes sense. So in theory, all clear loses a bit of gloss as it dries.
 
not really. all paint will shrink as it dries. solvents come out, paint film shrinks down. now your clear wont lose gloss assuming its a really good quality clear and its sprayed on a smooth surface. spray the same clear on a surface thats a bit textured then the clear will shrink down into that and you'll lose some gloss. your base for instance. if your using too fast a reducer and your spraying it on the dry side then that will kill some of the gloss in the clear. another way to put it and this is extreme......spray a coat of clear on a piece of glass, let it dry 100% and you'll have a nice clear with no loss of gloss. now spray the same clear on a piece of 220-320 sandpaper, let it dry. do you think you will end up with a clear just as glossy? of course not. the clear dried and shrank down into the grit of the sandpaper. im not saying this is your issue either. just a possibility
 
Alot is going to depend on how many coats of base like Jim said. Say you did a color that covered in 3 coats and waited overnight to clear then it really won't but if you sprayed something that required 6,7 even 8 coats to get coverage then waiting overnite and clearing might show some dye back, all conditions being equal. In time the one with the most base coats will be more prone to dye back then the other. Sometimes it might take a few days to dye back, I've seen them buffed back to a good gloss and still dye back later.

There are alot of "depends" when it comes to painting.
 
Dan,
You said the other day it does not happen at home only in class, so have to ask are you spraying the base or students? And who is praying the clear?
With that said and seeing many jobs you have done over the last 10 or so years, this has me just dumbfounded.
 
You said the other day it does not happen at home only in class, so have to ask are you spraying the base or students? And who is praying the clear?

Maybe praying over the clear would help me....but I'm not gonna spray any students..:)
 
Barry, I think you nailed it, the kids are spraying the base, and often the first coat of clear, and I'll go back in and wet in a final coat.
 
I sprayed some 2020 at school today, on a bumper that I personally based and it came out like glass....It must be the way the kids are spraying.
 
Here is something over the years I have learned and at first made no sense to me but seen it enough now to know its true.

IF the base is piled on or to a fast reducer or not flashed good, even if you let set overnight before clearing, it will not get rid of the solvents.
Took me years to agree with the above statement, and finally figured a way to do a test to prove it.
 
Barry, So I understand. Heavy multiple coats trapping the solvents in the previous coat(s)? Or fast reducer drying too fast on the top of the base and trapping solvents underneath?
I found out the fast reducer issue years ago, when I was starting out, why I always tell guys use the absolute slowest you can get away with. Buffed a car 3 times before the solvents finally escaped.
 
I'd venture to say its the way they are laying the base on, like Barry has said in the past and with using spi for a couple years now, for the most part it rings ever so true.. Slower is Faster. They're probably laying the base on way too heavy or hammering on the first coat of clear with possible incorrect activator or reducers for temps.
 
I having the same problem with the universal clear I sprayed my car all in same day let it sit a few days wet sanded n buff looked good but after couple months dyed back.then after 2yrs finally wet sanded and buffed again and couple months later I see it dying back a little not bad but when you are picky it's noticable
 
It's not the clear, it's everything under the clear gassing out remaining solvent, little by little. The Universal clear is among the highest solids material you can spray on a vehicle, so it's not a significant cause of the shrinking, especially because it's the last thing to go on and closest to the air where solvent can evaporate. But just like it is very resistant, once cured, to solvent attack from above, it will also resist solvent penetration from below as well, leading to a very slow final substrate cure if solvents are trapped beneath it.
 
Hmart- How about compound residue, fillers, lube makes it look more shiney then it is.
Someone here uses Windex after final buff to reveal truth.
 
EddieF said:
Hmart- How about compound residue, fillers, lube makes it look more shiney then it is.
Someone here uses Windex after final buff to reveal truth.
Click to expand...
Hmart said:
Hmm not following what u mean
Click to expand...

Eddie is talking about after buffing some compounds that contain a lot of fillers, the fillers wash away and you see the true surface...whether or not you have gotten out all your color sanding scratches. If you still have some sanding scratches it can look like die back.
 
I apologize I made a mistake it wasn't spi clear it was a different brand sorry I got mixed up I always buy old cars and fix them then sell when I get tired so I go through quit a few vehicles .the vehicle I sprayed the spin clear I sold it so I don't know how it looks after a few months
 
You must log in or register to reply here.
Back
Top