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Clear coat cracking

14K views 27 replies 8 participants last post by  69 widetrack 
#1 ·
I painted my truck in july of 2011. I was happy with the results and was excited about getting out the wax and the buffer for the first time this past summer but i noticed in the fall the clear coat on the hood began to crack. What would cause this the new paint held up great through its first fall and winter and shined up great this summer, why would the clear coat crack now? could the wax have something to do with it?
 
#5 ·
There could be many reasons why clear cracks...a few questions (like everyone else).
Is it the clear that cracked? or could it be anything underneath the clear, ie. bodywork, lacquer paint (as mentioned).
Are you finding clear cracking anywhere else especially a top panel like a roof?
What type of clear? Some clears are harder than others and if you have a combination of mil thickness of clear, body work (as clear, some fillers are harder than others and don't allow flex) and primers...If the primer is put on to thick or is a product that can go brittle after a while, cracks can develop.

The sad news is that you may need to take the paint down too and past the substrate to figure out what the problem is. It would be rare that if the clear was applied properly that it would crack without something happening underneath.

As far as waxing goes, I don't believe that would cause clear to crack....if anything it would cause clear to haze off. Some of the older high silicone content waxes seal the clear off to the point where over time would virtually suffocate the clear and cause it to die off.

Hope this helps...a bit anyway.

Ray
 
#6 ·
If there are any lacquer products, especially a spot putty like nitro stan, especially if it is a thick coat, this would cause problems. There's a lot of heat under the hood.
 
#7 ·
Is it covered in cracks, or just a certain area? What is under that area, body repair? Can you take some photos, are they lots of little cracks or longer ones?

Brian
 
#9 ·
Well there you go, your answer has been posted by others, uncured film and trapped solvents, you have both. That SS enamel can stay wet a long time, especially if applied heavy (read that a lot of overlap, slow gun movement, etc.) or too many coats too fast, too slow reducer, not hot enough surface temp, any or all of these things combined make for slower flashing and curing.

Now, under perfect conditions as I remember the window to apply clear over SS enamel is a much longer after the color is applied than say a regular Basecoat clearcoat. That is what I remember, but anyway you look at it applying clear over SS isn't the norm for a reason, it's a bit more temperamental.

Did you follow the tech sheet for recoat time and coats applied?

How many coats did you apply and how long did you wait before clear?

Brian
 
#10 ·
Not familiar with SS but that makes sense about longer flash times and a much longer than normal 45 min and clear, but I've never heard of solvents trapped leading to cracking...well, certain areas I've seen shrink up and sort of crack, but it's more or less like a rip or tear, but I could be wrong.

Was the car stripped? Was there originally cracks on the old paint that you thought you sanded out?
 
#11 ·
Henry, I have to agree with you about trapped solvents leading to cracking...especially the type described by the OP. Usually trapped solvents lead to the top coat, in this case the clear either delaminating after a period of time or popping (solvent pops) or hair checkered cracking ...ie wrinkling. This wrinkling (looking like cracks) would happen right after the clear was applied...not 6 months or a year later.

I also agree that what's under the single stage paint in all probability is the culprit, lacquer putty, filler to thick or to much hardner in it, wrong type of filler used like short strand fiberglass, mat fiberglass with to much resin and hardner...who knows until it's taken down to the source but, in my opinion there's something under the single stage paint that's causing the problems....to much time has expired for it to be top coating the singe stag.

Just my thoughts.

Ray
 
#13 ·
I agree with you Brian, if Coaner could post pictures, we all would have a better chance of helping him figure out what is going on with his paint. What might be cracking to one person might be wrinkling to another. We're all relying on Coaner's description and the cause of the problem is only our "bestest" guess...LOL.

Ray
 
#15 ·
I will try to post some pictures later im going to work on the truck. The cracking looks like somebody broke a hard boiled egg shell and is mainly on the hood all over it evenly. I didnt need to do any body work on the hood other than repair a few small dents. I painted the truck in July it was about 90+ plus that week using a slow reducer and waited longer to clear because i was told to when using the SS.
 
#16 ·
The reason for "cracking" in most any finish is the upper film gets hard faster than what's under it, plain and simple in my experience that is what could cause "cracking". The film under the clear has "moved" do to it being uncured and soft, just like the ground moving under concrete, the concrete cracks.
Die back of course as Ray mentioned is most common with this but "cracking" is VERY uncommon these days with Urethanes. So I am just going back to the old standard that when something is hard laying over something that is not, the hard cracks.

Brian
 
#17 ·
I can appreciate what your saying Brian but, that's why I asked if it was cracking anywhere else...like the roof. Sides, if what your suggesting is the cause, I can see them not cracking because you can't put paint material on as heavy on the sides as you can on a hood, roof or deck lid, (no deck lid in this case because it's a truck). So if the problem was a soft substrate underneath the clear the roof should be cracked as well. If it's only the hood...I'd like to know if the hood was painted off the truck. I've seen painters when they paint a hood off the vehicle just pound the material on...then I could accept the rational.
 
#18 ·
Often WAY more material is applied to the horizontal surfaces, so the question is, was it painted off the truck, or if it was on, does the cowl at the edge of the hood have the same cracking? If the cracking were to go to the edge of the hood yet the cowl isn't cracking and the hood was painted on, then it HAS TO BE something under the paint on the hood. Figuring out what happened is very hard with out getting all the information. Was the hood painted off the truck but hanging from hooks vertically? When you walk into a shop as a rep looking at a problem you literally are a cop looking at a crime scene and you ask many questions and look at what is in front of you. With just a few words on a forum is pretty tough.

Brian
 
#19 ·
Your absolutely right Brian...it's so hard to tell and that's why I was wondering if the cracking was anywhere else. In many cases like this, if the person who painted it saw what was happening and he was honest, the paint problem would be solved immediately. If it's only the hood that's cracking (not the sides, not the cowl not the tops of the fenders or any adjacent panel) the painter screwed up. How about this...the truck got painted, everything looked good except the hood, maybe to much dirt, a big bug right in the middle of the hood, whatever. The truck had to go and they had to put everything back together so take the hood off, re-shoot it while the other guys reassemble the truck....the painter pounds the paint on, throws the hood on the truck and see ya later. I've seen that happen more than once in a body shop (not the cracking paint part so much but taking a hood off to repaint it while the rest of the truck is getting the bumpers headlights grill etc. put back on it so it can leave a 5 o'clock)
 
#22 ·
Oh heck yes I have a ton of examples. But lately I had a pretty funny one. Our old head painter at work (he stepped down and rightly so) would match a color and then paint the car and the color wouldn't match, even though it did on his spray out card. :rolleyes: I showed him, I explained to him that this was PROOF that he was spraying it different, the application was some how different and he just never got it, just never could understand that the color isn't going to change unless YOU spray it different, being drier, wetter, less coats, SOMETHING is different about how you are spraying it if the spray out car is different than the fender you paint with the same paint in the gun for crying out loud! But he just never could grasp it. It was easier for him to blame the paint. :nono:

Brian
 
#20 ·
I painted the truck, first time painting a vehicle it wasn't perfect but i was pleased with the outcome and was glad with what i learned. The hood was painted on the truck, i took a closer look and it does appear to be on the horizontal surfaces more than the vertical portions of the hood so it makes sense that maybe those shifted causing the clear to crack. My other question is why a year after did it do it? Sorry for the questions but the more I learn the better I will get at it.
 
#21 ·
Realistically it simply took that long because it wasn't out much in the sun? Because the clear simply lasted that long before it "gave up". :( This is one of the reasons why I love it when a guy says "I do it and it works", that is fine but do you see it years after you have done it? That is often a whole different story.

Brian
 
#23 ·
for painting it's always better to know all the dos and don'ts before you even spray a gun. With bodywork it's get a fender, put a dent it, and heck, you could even somewhat fix the dent with two nice sized rocks if you had to saying unga bunga. For painting you have to read up on lots of details before even picking up a gun or you will be throwing away money. So I'm surprised you guys even had a painter that can't recognize that you spray a spray out card the same as you would the vehicle. This is all mentioned in I-Car and common sense. If he's I CAR platinum as I am at refinishing then he should know this. Is he I car platinum? The new role certified?
 
#24 ·
Henry, common sense can't be taught. And you can go thru an ICAR class and be handed the answers at the end, I don't know about you but the classes I have been to do basically that, tell you the answers to the test. Not only that, but if you have no passion in the subject you are simply not going to absorb the information. God knows I have been to a few ICAR classes that I couldn't tell you a darn thing I learned, it was a subject that bored me.

This guy, I don't know what to think about him, he has no passion what so ever in the science of paint. If you have no passion you can go to a hundred classes, you are going to walk away with nothing. Where you and I would test things and see where the boundaries are and so forth, he could care less, it's just a job.

Brian
 
#27 ·
Old Fool...You nailed it...As I have mentioned many times on this forum there are true painters and there are applicators....anybody can apply paint, it's how it looks and lasts that makes the difference between the two. For the OP and I'm not trying to offend you, Single Stage paint was not designed to be clear coated...I don't care what is said about this, the fact is when it's sprayed and sprayed properly it's designed to be shiny. If it wasn't, it wouldn't be called single stage...I think they might give it a name like "base coat, clear coat". If it was designed to be clear coated why would it have a shine after you put it on your vehicle before you put the clear on.

The top surfaces are cracking in my opinion because the Single Stage was applied to heavy on the top surfaces and the more product you put on the longer it takes for the catalyst (hardner) to completely react with the paint (You can catalyze a gallon of paint and it may have a pot life of an hour or more, yet you spray the paint and it's sets up in minutes, not cures but sets up). I don't feel that it's a problem of trapped solvents as much as trapped catalyst. You have a catalyst for Single Stage...it may have a part number like LSH80 and your reduction is 4 to 1 for example, your clear coat has a hardner with a part number like DQ7500 with a reduction of 2 to 1...2 part numbers that don't resemble each other, 2 reduction ratios that in no way shape or form appear to be compatible. When the catalyst in the Single Stage hasn't had the time to react with the Single Stage paint and is top coated with a product with an entirely different catalyst who knows how long the product will last? I'm not a chemist and unless a person applying the paint is a chemist it's good advice to stick the tech sheets.

As I mentioned, I don't want to offend the OP, in the future if you paint a vehicle and you want to clear it use base coat clear coat. Your chances of having a problem like this occur will be minimized. If you did it this way because base coat cost to much....well, it took over a year to find your answer why base coat costs more.

By the way...I do seriously appreciate that you want to learn and I'm sorry that you had to learn the hard way...We all have had things happen like this....sometimes I think this trade is more of an art than a trade.

Ray
 
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