[anthonycn]

Hi i just painted my brother's car around 3 months ago. i had use ppg dbc and ppg 2042 clear. I had prepped the car by sanding the old clear down with 600 grit. After i was sone with the clear i waited a day before I sanding down the clear with 1000 grit. Then sand it again with 1500. I used a da sander with the 3m finishing paper for both the 1000 and 1500. I buffed it out woth the 3m rubbing compund and wool pad. then polish. It looked great. The problem is now after 3 months the clear started to get dull. I looked really close and see very small da sanding mark. I dont understand how this could happen. I made sure i buffed it all out with the compund. Any help would be greatly aprriciated. Im about to paint my own car very soon and dont want this to happen again. Do you think its because I used a da sander? I just started to paint 2 years ago and this forum helped me out alot. Thank you in advance.

[Jag Daddy]

How soon after painting did he wash it? And what or where is he washing it with?

Regards
Mark

[anthonycn]

I had washed it a week after the paint job with meguairs car soap.

[302 Z28]

Personally I would not have used a DA sander to do the final finish sanding. That should have been done by hand IMO. It is possible that you could wet sand it again, then buff it out if there is enough clear left.

Vince

[Dbodily]

LOSS OF GLOSS
Dieback, Matting, Hazing, Dulling
A dulling of the gloss as the film dries or cures.

CAUSE
Topcoat applied in heavy, wet coats.
Inadequate flash time between coats.
Insufficient film thickness of topcoat color or clearcoat.
Insufficient drying/curling of undercoats before applying topcoats.
Using a poor grade and/or too fast evaporating thinner/reducer for spray conditions.
Improper cleaning of the substrate.
Insufficient air movement during and after application.
Spraying over a deteriorated or solvent sensitive substrate finish without proper priming or sealing procedures.
Natural weathering of the finish.

REPAIR
Allow finish to cure thoroughly, compound or polish to restore gloss.
Or, sand and refinish.


PREVENTION


Apply the topcoat according to product label directions using the recommended gun set-up and air pressure.


Allow all coatings sufficient flash between coats.


Apply sufficient number of coats to achieve recommended proper film thickness. Check with film thickness gauge if possible.


Allow undercoats to thoroughly dry/cure before topcoating.


Select recommended thinner/reducer based on temperature, humidity, air movement, and size of repair.


Clean substrate thoroughly before and after sanding.


For air dry situations:


allow exhaust fan to run 40 minutes or longer after spraying;


open booth doors after finish is dust free; and


maintain a shop temperature of 60 degrees fahrenheit or above, especially when drying overnight.


For maximum holdout, use a premium two component undercoat system.


Properly wash and care for the finish on a regular basis.


Using premium topcoat color or clearcoat system will provide maximum gloss and durability.

[302 Z28]

All the above assumes that the DA marks are in the clearcote, are you sure they are in the clearcote?

Vince

[Dbodily]

P.S. the above post is from a tech board I visit. Just wanted to make sure no one thought I was plagerizing.

[anthonycn]

Thank you for the fast response. Yes I am sure that there is sand marks in the clear. I looked really close at it and can see very small sand marks swirls. I used a da sander because my body shop supply store said it was the same as wetsanding by hand but much faster. Why would it just show up after 3 months? I had try buffing it out but no luck, gonna try wetsanding by hand later. Thank you

[willys36@aol.com]

Clear coat is incredibly (for plastic) hard and a scratch in it is difficult to eliminate. The DA was definitely a mistake but, hey, if I told you about all my mistakes over the years, Jon would eliminate my post for being too big! IMHO color sanding should NEVER be done with power tools. It is a labor of love an only hand sanding can so it justice. If I were you, I would pick up at the 1000-grit block-sanding step and progress to the compound polishing step. Follow that with a coating of 3M glazing compound , then keep it waxed with Mothers paste wax and it will say shiny.

[troy-curt]

I`m with willy on his post, Can`t imagine anyone using a da to finish sand clear I hope it was because of lack of knowledge of supply store clerk, and not laziness on your part.

Sanding clear is like foreplay,done with finesse, it pays off.

I would finish with 2000 grit, and a rubber squeegee.
And use a foam buffing pad.

Willy likes 3M glazes, and it is a good product, myself I like mequiar`s. HTH

Good Luck
Troy