Clear Coat boiling

serjik911

serjik911

Promoted Users
Hello everyone,
got a problem, and looks like i cant solve it without help.
after spraying have a good surface with no runs no dust or anything.
But in 4-5 hours, or if i bake it in 1 hour, i have the clear on my hood with a light boiling. Nothing on other parts. Only hoods.
my first thought was im doing small flash time between coats. waited for 30 mins between coats - same thing.
tried different pressure and different guns - didnt solve it.
tried different clears - same.
tried to do not use bake- same thing next morning.
Between base and clear -15-20 mins and im going with my tack rag thru all panels, and the paint feels completely dry.
another my thought that i put clear too heavy, but i dont have any runs, and on utube isee people smashing clear much heavier than me.... so i really dont know what is going on and i ask you for advice. got this thing for a 2 months already.
got a downdraft booth with a very good air flow.
here are photo of right after sparying and after baking.
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on this photo i have a mipa base PXR color, reduced with some medium reducer, our supplier sells it in 5 galllons. for clear has euro 2020 medium hardener, medium spi reducer. mixed 4:1:1.5
the only thing in my head right now- could it be because of shitty reducer in the base? its around 90 buck for 5 gallon. gonna try monday spi reducer for base
 
Not exactly sure what you mean by "boiling". From your pics it looks like dieback to me. What are you using for sealer and how long between sealer and your base? How long between coats (flash time) when you are spraying base? What you are seeing is trapped solvents evaporating out which kills the gloss to some degree. Yes the crappy reducer could play part in it. I would only use the SPI with SPI clears. It does make a difference, but I suspect that you are either not giving the sealer enough time and/or you are not giving the base enough time between coats. Combine that with crap reducer and it'll do what you are seeing. Clear looks a little heavy, you could probably turn your fluid in a little but the clear isn't the problem. It's the trapped solvents underneath. Pretty common when you are doing collision repair and gotta rush through stuff.

Go back read the TDS's on the sealer you use and the base. Follow the recommended wait time for the sealer before shooting the base, when shooting the base follow the manufacturer's recommended flash times, if in doubt always err on the longer side, i.e. if the manufacturer says 10-15 minutes between coats give it 15. Use a better reducer throughout. Follow what the basecoat TDS says for wait time before clearing. If you can't do that cause they are trying to make you spray a certain number of cars each day then stuff is going to have to be buffed cause there is no getting around flash times.
 
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Before I had my own shop, I worked for a high volume dealer and had to paint 8 cars a day to keep up. Never really had dieback or solvent pop problems, but what will happen sooner or later is delamination issues because of trapped solvent. As Chris said, it starts with the sealer, and any solvent trapped there or your first coat of base will cause lots of issues. That cheap medium reducer probably flashes quicker than a quality medium reducer, compounding the problem. I always use slow reducer, and always have, especially in a downdraft. It keeps the top open a little longer allowing the solvent to escape. You just have to give it time to flash.
 
on this work i didnt use sealer. had bondo done here and there, light gray, almost white primer. mixed from leftovers dark paint, did first tack coat and full wet coat right away to cover the primer. cleaned the gun , mixed the right color with medium reducer, wiped overspray with tack cloth- took about 15 mins. sprayed 1st medium wet coat, 10 mins wait, tack cloth, last coat to get perfect blend and to do not have striping or mottling- can be dry or medium or wet, depends on the color. clean gun, mixing clear, going to pee, drink some water come back, take the gun, trying to do not screw up pps cup, tack cloth- about 20 minutes. thats my usuall routine
 
in some way you are sealing in solvents. the cheap reducer here is key. many cheap reducers have a high moisture content. moisture screws with the curing of anything with an iso catalyst like you would use in clear or 2k primer. i would say the reducer is your #1 culprit. #2 is flash time. how long did you let the base sit before you cleared it? the longer you wait the better. even of base feels dry to the touch, it isnt. it takes a long time for the tail solvents to flash off. for base to fully dry takes 12-24hrs. 24hrs would be the best flash time you can give BUT i know that isnt always possible. just give it as long as you can afford.
 
if i will respray the hood today, just a clear, will it give me the answer if the problem is in my base coat?
 
The problem is in your undercoat and the reducer. To answer your question IMO no. It's not a clear issue, it's a reducer and flash time issue and it will continue as long as you use that reducer and push the limit on re-coat time. Use a quality reducer not that recycled garbage. Only thing that stuff is good for is cleaning your gun. Being that you have a heated downdraft booth use a step slower reducer. Slow (or extra slow) is what I use all year round. Works great with a crossdraft unheated booth. (collision repair).
You can have quality or you can have quantity, but you really can't have both. Want it nice, you got to give it the time it needs.
 
so, i asked for coworker to spray clear on hood on his car.for free. took a photo of it. a lot of fish eyes and crap but not important. sanded with 600 and shot the euro 2020. mixed 4:1:3, 2 bar, 4 out fluid with ws400 1.4hd. sprayed 3 coats thin as possible but wet coats. 15 mins between each. looks like that before baking.
 

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Spi or cheap reducer you didn't mention or activator.
My pinhole problem vanished when i dumped cheap local reducer & went slowest possible activator.
Also how dry is air coming out gun? All these cause problems.
 
ok so after 4 hours drying. no die back, just a light solvent pop
 

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That first tack coat followed immediately by a wet coat could be part of the problem, also. That first tack coat still has solvent and wetting it too quick to get coverage will trap it. The most important flash times are after the first coat of base, after sealer when you use it, and before clear. Sherwin Williams advertised a prime to shine system in 40 minutes or less. Guaranteed delam problems to sell product, IMO.
 
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Euro tech sheet says if doing 3 coats, wait 30 min between coats. That means all of the coats. Also, I didn't see what the booth/ panel temp was and what your speed of chosen activator/reducer was. Maybe, I missed it.
 
ok so the problem was that i put too heavy the clear. the dropplet was too big. my gun adjustement were wrong( low pressure and closed fan too much) , so the gun didnt atomize well. sprayed 2 parts today, one with a high pressure, full fan and 2.5 open fluid and had no problem, and second part i sprayed with my old style, around 20 psi, fluid full open and fan closed like 2/3 from open- got same die back as on first photo
 
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