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TOPIC: Paint hardness and gloss reduction

Paint hardness and gloss reduction 1 year 7 months ago #28782

  • Rel
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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.
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Paint hardness and gloss reduction 1 year 7 months ago #28783

  • rikka23
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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 clear

These 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
Last Edit: 1 year 7 months ago by rikka23.
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Paint hardness and gloss reduction 1 year 7 months ago #28787

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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.??
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Paint hardness and gloss reduction 1 year 7 months ago #28820

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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.
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Paint hardness and gloss reduction 1 year 7 months ago #28823

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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.
Don't eat yellow snow!

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Paint hardness and gloss reduction 1 year 7 months ago #28832

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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.
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Paint hardness and gloss reduction 1 year 7 months ago #28834

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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 Nexa

Another 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!
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Paint hardness and gloss reduction 1 year 7 months ago #28892

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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!
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Paint hardness and gloss reduction 1 year 7 months ago #28893

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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.
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Paint hardness and gloss reduction 1 year 7 months ago #28896

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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.
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