how soon is too soon to color sand?

[1BADRS]

Quick question.
Wet sanding. I hear anywhere from a few hours to a couple of weeks to start clear sanding and buffing.
Opinions needed.
Pros and cons of sanding to quick, and waiting too long.
Thanks! :help:

[dhutton]

Some good advice in here:

http://www.southernpolyurethanes.com/perfect%20paint.htm

Don

[1BADRS]

Some good advice in here:

http://www.southernpolyurethanes.com/perfect%20paint.htm

Don
Thanks
From two days to two weeks after the job has been completed, wet sand the clear

[cheapthrillz]

Most that I've seen usually color sand after a day of curing. If you wait too long and the clear hardens too much, then it will be really hard to get out the imperfections in your clear....

I'm not a painter, but I've watched it done... and done a little wet sanding...

Hope this helps.

[63SW]

I myself usually wait till the following day ( DEPENDING ON HOW WARM OR COLD IT IS )
70-85 deg. - i usually start to wetsand the next day and work till im happy with it all..Usually a couple days of sanding easily .
I start with the finest grit i can ( NO NEED USING SOMETHING TO COARSE AND CAUSING SCRATCHES YOU HAVE TO TAKE OUT LATER )

start with 2500 ( if thats not getting it - move to 2000 , so on so on till you get what you need , then work back to 2500-3000.

Thats for urethane Base clear ( check for whatever materials you use to make sure )

Thats my thoughts , BUT WHAT DO I KNOW - Im just a local garage monkey doing it at home im my garage !

Heres one i did not long ago.

[70 Chevelle]

I've done a few paint jobs and find that the longer I wait the better they turn out. There just always seemed to be a little shrinkage somewhere and letting the paint sit as long as possible allowed me to cut it out . Are you guys who are cutting the day after baking your paint? I do not have access to any type of baking lamps. I even go as far as letting the car sit for a month after all body work and primer has been applied to avoid shrinkage at any costs and putting the car in the sun as much as possible if the weather allows. Time really isn't a priority as I only paint my own cars and they are not my daily drivers. I've always wanted to find an easier way to do this as it usually takes me a week or more to cut and buff when the paint has been allowed to harden that long. I do all of this to avoid those tiny lines that pop up 6 or 7 months after you've finished.I know these time lines are ridiculous but would love to know how those who don't have lamps avoid this.

[63SW]

I dont have any lamps or other curing devices.

I do let my body work and primers cure but using some of the new ureathanes its not as much of a problem as with the old laqure.
the materials that require a catalist dont seem to shrink as bad in my opinion.

Im sure if your waiting that long , its hard and you have to work your butt off to get a high gloss finish.

i think the tiny lines you mention are in the bodywork and primers.
thats where guide coating comes in and allowing the primers to cure before blocking the car out.

for me , a week is to long to wait to cut & buff - its just harder and more time consuming.

again , just my point of view.
RIGHT - WRONG -? everyone does it different !

[brigzee]

There are pros and cons to both. The sooner you do sand and buff the easier it is. The longer you wait the harder it is but will stay looking good. Paint takes up to 3 months to cure and get all the solvent out. So if you buff early on the paint is still curing and there is a chance you will have to go over it again after a few months. Even if you wait to long finish sanding with 3000 grit and it will buff easy with the right product.

[Alchemist]

If you'll pardon me please. I would like to clear up the terminology.

FYI - The term "Colorsanding" refers to sanding "color" (either dry or wet) whether it be basecoat of single stage color.

The term "Wetsanding" refers to sanding with a liqud medium - usually water (though in the "old days" gas was sometimes used in substitute of water) - whether it be color or clear coat.

I started learning to paint in 1971 and from my years of experience I still haven't come up with an "average" of how long it takes for paint to completely dry. I truly believed with the new catalyzed urethane paints it would be more conclusive to determine this. Only to discover it still isn't. I've spoken to many paint reps who claim it takes this long to dry - each one having their own opinion. I've spoken with chemists who have assisted me tremendously but even they have confessed to me that they're in a laboratory not in the real world applying the stuff! Painting a car from a restoration standpoint is quite different from collision repair paintwork. I'm speaking from my years of painting in automotive/airplane restoration - just for clarification.

So many variables come into play that affect paint dry time. If you paint the car in winter or the summer - each and every day the temps can/are different as well as the time of day. How soon you get back to sanding and reapply more product and how much DFT (dry film thickness) is left after sanding etc., You get my drift.

My general rule is to wait. I would suggest that you dry sand the clear coat with 1000/1200 grit using an orbital sander to break open the surface of the clear to help purge the remaining solvents then waiting another week or two. You needn't sand the surface to remove all the orange peel as though you're getting ready to polish.

There are isocyanates in clear; and what happens to clearcoat when you wetsand if the clearcoating is not fully cured; you "re-case harden" the clear. Meaning you relock in the solvents, which is not a good thing if you're wanting to polish. It will shrink or dieback. So, it is better to wait than to rush to cut and polish.

An alternative is to use the orbital/dry sand method of polishing. I find this to be good on large flat or slightly curved panels. You must use extreme caution if you have sharp lines on your body panels because you can cut right thru to metal in a blink of an eye. The drawback I've experienced with this method is that it will always dieback (dull and mini-orange peel) if cut and polished too soon. You will need to repolish like "brigzee" already mentioned.

As for clear coats being hard to polish if you wait too long is not necessarily true. Every clearcoat manufactured is designed with specific performance characteristics and has a specific polishing window. Here's an example: Dupont's IMRON system clearcoat was designed for industrial use; to be virtually impervious to the abuse placed upon it in the industrial industry like the cement trucks etc., IMRON clear was NOT designed to be cut and polished which alot of us custom painters discovered! It was meant to be sprayed and left as is. You could sand and bring it to a gloss but you could not remove the finer scratches - thus it was like polishing concrete!!

There are more user friendly clears developed today. Meaning you could polish it a week from today or 3 months from now and it would still polish easily. I would suggest before you paint anything, to pick up all the product sheets on the materials you are considering to use and read up on the technical data providing the performance characteristics and also the time constraints you have for topcoating/polishing etc., Some clearcoats are designed to be polished within 24 hours but I would recommend you stay away from this type of clearcoat unless you're painting a schoolbus or a garbage can. You can obtain specs by obtaining the product sheets for that particular clearcoat.

[grumpy44]

when u get ur desired paint make sure u get a product sheet with it, it will tell u everything u need to know about that paint, dry times, film thickness, thining rates, how to apply, tape time and whatever else u might want to know. I think its caled a safety data sheet, Been so long sense I got 1 I can't remember. Anyway, the clears they have out now r pretty good about color sanding it the next day. I myself, if I have the time, let it dry as long as I can. Most the time it just depends on what manufacturer made the paint.