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2k clearcoat

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Location: Newcastle, England
PostPosted: Sat Nov 20, 2004 3:56 pm
Hello to everyone. My very first post, I have browsed these forums constantly picking up tips before I sprayed for the first time.

Here in England we call 2k - 2 pack, and clearcoat is referred to as lacquer, thinners - reducer? (just in case I forget and state the English term for it).

My question is when I was mixing up the cc, it had 2:1 on the tin, I added the hardener (activator), and 10% 2k thinners, now I'm not sure if I should have added the thinners or not. Will this matter?

The panels I have painted so far have turned out amazing for a first attempt with the exception of two which one has a run and the other has dust trapped. But not bad out of all that makes up two motorbikes.

The panel that has the run (first one I did) I did not apply any clearcoat to it as I thought it was pointless if it needed sanding etc, I plan to follow advice on a post on here and trim it right down with a bent razor blade and wet and dry it with 1500 grit. Was I also right not to apply the clear to this pannel, or should I have applied it.

Any advice would be appreciated



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PostPosted: Sat Nov 20, 2004 9:39 pm
Thinner is only used to make the paints thin enough to spray from a gun so using it will not hurt anything, it will however make the layers of paint thinner and you will have to apply more coats to get the final paint thickness. You should clear the panel then fix any problems and repaint, when you sand base you bring the wax to the surface and you kill any chance of adheasion to clear.



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PostPosted: Sat Nov 20, 2004 11:07 pm
WAX?? INNA PAINT??? Frank...'Splian yoreself boy.......

Hi Frank. I have heard that some outfits are putting wax in the paints because of oxy-inhibition.....I just didn't know they were dumb enough to put it the paints that often. ...No wonder I keep hearing about paint peeling off cars.

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PostPosted: Sat Nov 20, 2004 11:41 pm
Yeah, Frank please tell us more about this. I had heard the guys down at my local supplier talking about "wax" in the base. I know we can still buy "waxing lacquer" in the furniture refinishing biz. It's used to give a "soft look" and "hand waxed" feel with a lot of the imported crap that comes from China, etc. I just thought the guys down at the paint store were nuts when I heard this referenced to automotive grade finishes. Please enlighten us as this may explain why paint films prematurely fail.
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!

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Location: Newcastle, England
PostPosted: Sun Nov 21, 2004 4:18 am
Thanks for the reply, the thought that sprung to my mind was it would be pointless clear-coating the pannel if I had to scrape back through it to remove the run.

Well I will live and learn
muchios gratias



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PostPosted: Sun Nov 21, 2004 9:26 am
Sorry to get everyone all worked up with no imediate resolution, I was the type of painter who liked to denib my base, I mentioned that to one of our training center instructors and was yelled at for it, apparently everyone uses Parafin wax in the base but I am not a chemist and was not told why, I will make some calls tomorrow and find out what the exact reason is.



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PostPosted: Sun Nov 21, 2004 10:04 am
Frank, The only reason I know of for adding wax is that some resins (polyester ) don't cure at the very surface, and remain a little gummy. The wax is supposed to float to the surface and block the air so that the resin will cure at that surface. This is why I started using only laminating resins a long time ago. (they don't have wax)
G

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PostPosted: Sun Nov 21, 2004 10:16 pm
Here is what a FEW Paint Manufacturers recommend for re-basing after sanding to repair an area:

"Sanding:
DuPont ChromaBase® base color dries to a smooth matte finish and should not be sanded. Nib sanding of small areas to remove dirt must be followed by the application of more color before clearcoating."
DuPont Website Link - PDF File

""Sanding:
DuPont ChromaPremier® Basecoat dries to a smooth matte finish and should not require sanding. Nib sanding of small areas to remove dirt must be followed by the application of more color before clearcoating."
Dupont Website Link PDF FILE

"SANDING OUT IMPERFECTIONS:
S&W DIMENSION Basecoat
To sand out imperfections after 15 minutes, wet sand 600 grit or finer to remove dust, dirt and to level surface. Must rebase with one or two coats of basecoat."
http://www.sherwin-automotive.com/media/pds/6035.pdf

"Special Notes:
Martin Senour Tec Base
• Do not scuff sand (wet or dry), or solvent clean basecoat before application of clearcoat. (Small areas may be wet sanded to remove dirt, and basecoat re-applied.)"
http://www.martinsenour-autopaint.com/p ... h/8500.pdf

"Sikkens
SECOND REPAIR: If, during the application of Autobase Plus (OE) Solid or Metallic color, some damage occurs such as dust impregnation or perspiration spots, allow the Autobase Plus (OE) to flash off for 40 minutes at 70°F (20°C). Lightly sand the damaged area with #P600 to #P800 grit paper wet. As there is no clearcoat to protect the base coat at this stage, care must be taken to clean up all sanding residue. Proceed by making a spot repair as described in the TDS, "Spot Repairs with Autobase Plus (OE)."" IN OTHER WORDS REBASE
Sikkens Website PDF File

"SANDING AKZO Nobel U-Tech Polybase: If sanding is necessary on the basecoat, wet sand with #P600 to #P800 grit. Then recoat."
UTech Website PDF File

"Repair of R-M Diamont Basecoat
1. Allow Diamont Basecoat Color to dry for 30 minutes or longer at 20°C/68°F before sanding.
2. Wet sand using 1200 grit or finer sandpaper to remove small imperfections.
3. After sanding and repairing Diamont Basecoat Color, additional Diamont Basecoat Color must be applied over the repaired area. No special reducers or spray techniques are required.
4. If hardener has been added to a basecoat color, hardener must be added to the repair basecoat also. "
http://www.superiorpaints.com/rmtech/DIAMONT-1-41.htm


A lot of Paint Companies recommend RECOATING after sanding the Base Coat.

PPG doesn't really address re-basing after sanding out dirt nibs and such in their product sheets. I've always re-based after sanding before the clear coat. I highly doubt PPG has a secret formula that allows them to not rebase after sanding - repairs. Again doubt PPG will advise anything other then to recoat with their base after sanding.

The biggest reason you recoat after sanding the base coat is to prevent adhesion problems when the clear is applied over it. There are resins that rise to the top of the base coat and provide chemical bonding with the clear coat. It is removed during the repair -sanding process and that is why it must be re-applied ie: recoated for the base coat before clear coating.
Base coats are usually kind of thin on application too.
Most if not all Base Coats dry to a soft velvet like sheen - they are not glamour shiny - the shine comes from the clear application.

If you used a kicked base coat ie: activator then you can sand it down and apply more. If you kicked the base with an activator then you must also kick the base used for the repair. If you did not kick the base coat then might run into wrinkling and such for problems if it is out of the recoat window. Most repairs to just the base coat must be done within the time window ie: check the product sheets for your paints. Sometimes you can seal it with the Clear Coat and come back with more base and that is probably why FrankS gave that advice.

To knock on some doors:
These Paint Companies are not trying to screw anyone and make them use more of their bc products with this information for re-basing after repairs. They are trying to give you SOLID advise that will keep you from screwing up AGAIN. Remember you have already screwed up if you need to make a repair in the first place. Right? Don't screw up twice. Take the Paint Manufactuers advise as provided on the Product Sheets and move on to the next stage.

Again If you don't re-apply base after sanding then WILL have an adhesion problem down the road between the base and the clear. The next coat of base will bond with the old base if it is applied correctly. Do not dry spray the bc DRY or there will also be an adhesion problem.

For the life of me can not understand why people do not want to read and or understand this information? Some people are just bound and determined to learn the hard way. I DID and it is called: "The School of Hard Knocks." :)

I believe: Most paint failures with modern urethanes are the FAULT of the Individual Applicator/Painter. Will admit there is probably a small percentage of product failures. With new people there are several factors in the element for a potential screw up and one is inexperience. We have all been there and done that. It is hard to admit and say "I" screwed something up. That is part of learning sometimes too. :)
Last edited by D71 on Sun Nov 21, 2004 10:42 pm, edited 1 time in total.



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PostPosted: Sun Nov 21, 2004 10:41 pm
Sorry, D71...We are referring to the failures of the factory paint jobs...which still happen on a regular basis. The in depth explanation that you offered is interesting reading, but doesn't mention anything about wax content or the reasoning behind it...Do you have any info on that to add to what I have posted? I'd be interested in learning what new reasons they have for adding release agent to paint.

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PostPosted: Mon Nov 22, 2004 9:12 am
Yeah, I really wasn't talking about the human factor either gst. I too, was just wondering about that in reference to factory applied coatings. Sorry to open a can of worms here, just trying to understand more about what makes up quality coatings.
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!
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