Paint hardness and gloss reduction
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Ladies and Gentleman,
First of all, i apologize for my english :blush:
I have a problem. At the shop were i work my colleague ( this guy unpacks the cars, polish dust nibs and that kind of stuff)told me that the painted objects after baking are not hard, or hard enough. And in some cases the gloss regreases a bit. My foreman and i are the painters at the shop, the problem seems to happen to both of us. We both have different styles in painting and use different guns. I work exactly like the TDS and im using all the products in the right way.
The colleague told me that on the blended panels were only a new coat of clear comes, the hardness is a bit better.
I doubt this, but i need to test it first ofcourse.
So yesterday i painted an old hood to run some tests. You can see on the pictures below.
I divided the hood in 3 parts. The first part i applied a coat of wet-on-wet primer, a waterborne basecoat, and 2 coats of clear. 2nd part i applied a basecoat and 2 coats of clear, 3rd part i only applied 2 coats of clear.I did everything like the TDS, and baked the hood. After 15 minutes of cooling down i put on a glove and pushed my thumb finger pretty hard on the 3 parts. It seems there was no difference in hardness between the 3 parts. But slowly the print dissapears almost completely. if i rubbed it with a towel it was completely gone. After an hour i did this test again. IT Was harder then before, but still a bit of a print.
About the gloss reduction, there wasn’t anything to see. It was the same after i apllied it. The last time i checked was about 2,5 hour after cooling down. My foreman told me that sometimes after a day you can see the gloss reduction. So i have to wait till monday if anything happened.
The thing is, i work at a high pressure shop, so after baking and cooling down the cars will be prepared for mount and leaving the shop. There is no time for some jobs to wait a day.
So any of you with some ideas, or awnsers? Is it normal with other clearcoats after cooling down you can left prints?
PS: on the last picture you can see the fingerprint.
Hey mate I understand where your coming from as I’ve had this problem with different products,
First with the clear coat, which kind is it as for example you cans get medium solid which is great for your everyday car, then there high solid for great gloss, scratch resistance, slow solids for smart repairs.Fit the polishing I never polish the same day as I find its to fresh and the next day you can see where you’ve polish. I’ve learnt from the past the clear can stay soft due to…
To much material and not fully coured
Not baked for long enough or at the right temp
Try and out the clear tins in the corner of the booth to warm up and help get a better flow
Also having the right speed harder for the clearThese thing help me to get the clear just rite to match the style of job your trying to get, hope it helps
I have noticed that when I’ve used a wet on wet or sealer then based and cleared it does leave a dryer finish, so when I do use it I do an extra half drop coat of clear
Also thinking bout it is the guy using the right, compound, the right speeds and coupons heads, as there’s so many different kinds. If your using the a compound try to use the same make for the machine heads, some of them are to harder for some makes of clear
when i switched to the wb paints, i had dye backs pretty bad, and found out i wasn’t giveing enough flash time before clearing, even when i used slow clears. so a little more dry time helped, as well as improving my paint technique of the base.
as for the clears, i have 4 i like to use, all are high solids, 1 poly, the other acrylic. two of the acrylics, i can buff with in an hr after bakeing, the other i can not, as if will be fine to start but the sand scratches will come back thru a while later. the poly, i can sand it at the end of the day, and have to wait a full day before buffing it, to keep the scratches from comeing back.
as for your detail guy, you need to find out what he useing to finish the job. i use a med. heavy cut cream with white foam pad, and finish with a blue swirl remover. we use 1000, 1500 depending on the situation, and finsh with trizact 3000 to make the whole buffing experince better. also how long is your guy waiting before doing any buffing. the p-sheets give an x amount of time after cool down before polishing.
the nice thing is, that you and your boss are haveing the same problem. or maybe it’s the detail guy that is having the problem.??
YOur clear may just not be suited for that speed. When I used PPGs envirobase, the ehp clears were relatively dry after bake/cool down but would finger print easy. There, we let the clear dry over night before handling/polishing. A little accelerator did help, but wasn’t a real solution.
As for the die back (lack of gloss later on), you may need to increase flash times with the base and in between coats of clear. Have you ever run a mil-gauge to see how thick your clear is being applied?
I imagine the PPG clear is very similar to the Nexa clear you are using.
A couple things,
How fast of a clear are you spraying? Is it a slow clear or a fast clear?
How long does the TDS say to bake and how long are you baking for? Remember almost all TDS states a drying time at metal temp.
The Enviro clears are Nexa clears watered down (reduced). I use Nexa clear but in an air dry enviroment and let set overnight before de-nibbing/polishing with no issue.
Thanks for your replys guys!
This morning is was checking the test panel i painted saturday.
At all 3 parts i did the fingerprint test again. It seemed the panel was hard.
However, when i put my nail in it, it leaves a mark.
This was only on the first 2 parts were i applied the basecoat.
The die back ( i guess i should call it like that) or the lack of gloss only happened on the first 2 parts of the hood, and not at the the 3 part were i only applied an new layer of clear.
The first part was the worst, 2nd part also but less.So my technical guy from PPG came over to take a look.
He agreeded with the dye back and stuff. He also checked the booths but everything seems ok.
He changed the flash off time of the booth, so it is about 2 minutes longer and the temp. will go up bit higher.
So we cant tell yet what it is, but it seems its in the base.About the clear that im using. Its the HS+ express clearcoat. P190-6659.
But we checked it and everything seems fine, from start(mixing) to finish(aplly)
I know the bake time is at metal temp, so we are sure that isnt the problem.
So this clear is made for speed, and the fastest from NexaAnother thing i forgot to tell you guys, i painted another testpanel on saturday.
This was a 2k uni solid color. the P471 line.
This one doesnt die back and is still shiny and hardness is good.
i did the fingerprint test, and it was much harder then the other waterborne panel.So today i painted a volvo, and it seems i did a pretty good job, but we’ll see tomorrow morning 😉
Im going to paint some more testpanels to figure out whats best.So, any suggestions or comments, please let me know!
Thanks guys!I had clear die back 2years ago.i was working in a part time shop and they r using Wanda waterbase. I can not remember what clear was that. The clear has low shine at the area where I put base,but the blend panel is good.tried so many way to solve this problem .then everything is ok after changed clear coat! So In my understanding is some clear can not work with some waterbase paint!
I have never used that clear and I don’t know what thinners your using in it either so here are some general notes.
It appears to be a faster clearcoat. With faster clears you want to minimize flash time between coats and also before bake. The longer they sit the more they die back.
Also faster clears tend to fingernail mark for a bit longer than slow clears. They are fast on the front end but cure slow where a slow clear will take a longer time to bake but will get harder quicker. The next day faster clears will mark easier.
Usually when you use a faster product you will give up some appearance also.
Again these are general guidelines as I am unfamiliar with the product your using. It may behave completely different.
U need to make sure that the wb is dry enough before clearing, 15 mins. I know i had the same issue, with the base on
He dye backs.
I use dc3000 & dc 4000 clears, 3000 being the fastes, but if i use a slow hardner iy does take longer to harden. Generally i stick with the fater hardners, i also dc2000 fast air dry clear, wich works very well wiith the enviro.When i need to do a big job, i’ll use dc4000 woth dch3070 hardner, keeps the glss & get the 10 min. Bake time as well.
Also with dc3000 the flash times r important, any longer then 5 mins i be better off leti g it air dry. I don’t know what % your reduceing your base, but i have bumped it up to 30, works well with dry times.
as general rule of thumb i have found the slower the cure the higher the gloss retention also in my experiance after bakeing the panel normaly requires a period of cold to harden up ,left in a warm still envoiroment clear often stays soft ,also i like to get vehicles out the oven and not left inside them overnight ,preferably outside in the open air and let the cool night air do its job
Basecoats and primers tend to act like blotting paper and soak uo the gloss ,when it comes to custom work i often double laker the job ,the first coat of clear acts like a sealer and the second will have superior gloss retention ,however this is not realy practical for the avergae bodyshop repair
most clears actualy have a full cure period of some 90 days
Paul
He guys! Thanks for your replys, again!
Well it seems the problem i have has something to do with the air velocity in the spraybooth. (don’t know if im using the correct english words)
Another technical guy from PPG came by to take a look at the problem. This guy knows really much about paint and also about spray booths. He did some measurements and came up with this problem.So im gonna try to explain it to you guys.
If i spray for example clearcoat (or basecoat, it doesn’t really matter) i apply one or more coats. So when i lay down my first coat, and wait to put on my next coat, this is what happens:Because there is a to high air velocity in my booth, the top of the coat will close or dry to fast. what happens next is there are still some solvents and other chemicals under it, that cant get out anymore. So then i apply my next coat and let it bake. the thing is, i can let it bake till christmas, it will never get completly hard.
So imagine what happens if i put a few coats of base, wich got the same problem and the 2 coats of clear, it will stay soft and the solvents cant get out, so it never gets hard.
To test this i painted an old hood outside my booth. i let it dry for a while and after some hours i wanted to give it some heat, so i put an infrared dryer on it. And….. it was hard :exci
Ofcourse there need to be done some more tests, but next week some technical guys come over to fix the booth and we will see what happens next!
Anyway thanks for all your input and help!
And lets hope i can paint like glass again! :whistle:I’m not in your shop, nor do I know what is actually going on. One thing I do know is that a lot of these paint reps – and i’m not saying all of them, but alot of them – will come up with some outrageous explanation of why you are having problems, just because they won’t want to put the blame on the product. 1. because their pride, 2. because they don’t want to risk having to pay you money to redo anything under warranty.
I can’t talk for anyone else here, but I know over the years of doing these repairs, there has been instances where i’ve had to rush small spot repairs, etc. I’ve put wet on wet on wet coats of base, not even let it flash off properly, and then dump clear on top of it. When it hardened, it was hard, and that was it. To top it off, thats with no bake cycle or anything else because I currently do not have a spray booth. It’s a bad example, and bad practice to do that, I’m just using it as an example to say that I personally Do Not think air flow in your booth is causing your clear to stay soft.
If I were you, I would personally try a different clear all together and see if you have similar problems. Usually if clear dies back due to solvent trying to evaporate and not being able to come through the surface, it was die back within 24 hours, and cause solvent pop on top of it. Clear dying back 3-4 days later seems like defective, or shit clear to me.
i have to say i tend to be in agreament regarding paint reps ,they have a list of excuses longer than the tech sheets all ready to hand out
however before we tar everyone with the same brush i would be very interested in the final outcome of this little saga as the info could be very usefull
Paul
X2 on trying another clear.
Sounds to me it is more of a problem with the surface flashing off to fast, either to much air movement or humidy issue…..
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