Problem with clear getting hard

P

Porsche 356

Hello,

In September I painted two Porsche 356's with base/clear. On one I used Universal Clear 4.4 VOC and the other Universal Clear 2.1 VOC. The car that was painted with the 4.4 was done using SPI's Perfect Paint Job method (six coats of clear) and the 2.1 car had four coats applied the same day with 30 minutes between coats. The 2.1 car's clear is hard but the Perfect Paint Job car is still a little soft. By soft I mean I can press my finger nail into the paint and it leaves a small mark. My question is why is the six coat job still soft? I have rubbed the six coat job and it looks very good.

Any help or ideas would great.

Jim
 
You mention 6 coats. Did you do them all in one session? Or did you spray three, wait a week or so, color sand and spray three more?
 
lots of variables here. in general a 6 coat job will take longer for it to harden up than 3-4 coats. how a clear hardens is directly related to temp, flash time and most importantly humidity level when it was sprayed. how long each coat was allowed to flash and be exposed to that humidity plays a big factor and goes hand in hand with the humidity levels on that particular day. higher humidity and longer flashes will make a clear cure harder and faster.
 
Jim C said:
lots of variables here. in general a 6 coat job will take longer for it to harden up than 3-4 coats. how a clear hardens is directly related to temp, flash time and most importantly humidity level when it was sprayed. how long each coat was allowed to flash and be exposed to that humidity plays a big factor and goes hand in hand with the humidity levels on that particular day. higher humidity and longer flashes will make a clear cure harder and faster.
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The temperature was 80 to 90 degrees the two days the car was cleared. I used slow activator. I sprayed three coats of clear with 30 minute flash time between coats. Placed the car in the sun for three days then sanded it with 800 grit and applied three more coats of clear. Then three more days in the sun. I did not start rubbing until the clear was a week old. Humidity was about 15 to 20 percent. I live in Sacramento California.
 
you did everything correct so you really dont have an issue here. the humidity is basically non existent at those levels so it would not be uncommon for 6 coats of clear to take a year to really harden up. of course that depends on how much time the car gets to sit and bake in the sun. typically when i paint a bike that has 6 or more coats i will be able to leave a mark with my fingernail for about a year. bikes here will generally see the sun on the weekends for about 1/2 the year.
 
Rule of thumb for each coat of clear you can leave a thumb nail mark for just less than a month. (not true with production clears or low solids)
Six coats on a black driven a weekend a month I could finger nail about 5.5 months, the nine coat one was right at 9 months.
It means nothing as can still buff and drive. Speed and long term durability do not go hand and hand.
Now non of the cars I have done are in sun all day but just 7 full days will shorten the above statement.
The one vette I put on 4 coats and for next few weeks if not going to rain I would pull out in sun before I left for work, than wet-sanded and it was out another 7 or so days (don't remember) after i buffed it a few weeks later i could not make a nail mark.

Production clears tend to be nail free in 1 to 3 days, you don't want that +hit on a 356. SO nail mark testing is very important to me.
 
barry, in all the years i have been using your stuff i have never tried your production clear. does yours get alot harder than universal and euro, or are your referring to most other paint companies production type clears?
 
I have never used the production or 5000 except for testing when we make a batch, my test is one coat so don't know.
Usually these two clears in a production shops are never applied more than 2 coats so they are getting hard fast.

Only thing I can say is a shop did used production on a show winner he did and some parts had 4 and some had 5 all in one day and he did call me a week after saying " I may want to kill my painter if he did not mix this right" but a week later you can still thumb nail.
I said buy the painter lunch as he did good and it will cure up good after body is on and gets a few days sunlight.
Jim, that is my only experience.
 
I'm having a similar issue with my paint job. So I painted the car with dynacoat base and clear pro at the end of august last year. I put on 3-4 very heavy coats of clear. I let the paint dry for a few days then wet sanded and buffed, did not gum up the sand paper at all and buffed out nice. I parked the car out in the sun for maybe a couple weeks before winter, then it sat in my cold garage all winter, Wisconsin winter so very cold. this spring I've had it in the sun for about a week now. I can still leave a very small thumb nail mark in the paint if I push really hard, but not on every panel, paint on some of the panels seems harder. is it possible that it just needs more time to cure? or do some clears just not get as hard as others?
 
it may just need more cure time. its hard to say as every clear is different. i dont think many people here have any experience with the clear you used so we are just guessing. i would guess that it will harden over time and dont worry about it. could be weak activator, improper mix or just a naturally soft clear that isnt meant to be sprayed that many heavy coats.
 
Jim C said:
it may just need more cure time. its hard to say as every clear is different. i dont think many people here have any experience with the clear you used so we are just guessing. i would guess that it will harden over time and dont worry about it. could be weak activator, improper mix or just a naturally soft clear that isnt meant to be sprayed that many heavy coats.
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My paint supplier used to carry Dupont, now they switched over to dynacoat, this is the first time I've used this brand, I believe it's made by akzo nobel. thank you
 
Jim C said:
Yea the base is wanda. Not sure about the clear
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I'm actually planning on respraying it again, I hate to but I have to, it developed about an 8' crack where the quarter panel meets the roof, 73 camaro, not sure if the primer shrunk or the body filler cracked but I gotta fix that, I have a ton of paint left over and the car is not assembled yet so I'm just going to wet sand and respray the whole thing, this time I'll keep my coats a little lighter.
 
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