Between Coats Question

[silentdub]

I'll be spraying a car this weekend, 2 stage. I'll probably do the base Sat and the clear on Sun.

Other than a tack cloth, should I do anything between the two? Wipe or color sand?

Obviously if I see any flaws in the base, I'll sand and respray that area.

[Bob K]

My preference is to put the clear on as soon as I get the gun clean. Why push the recoat window? That window doesn’t slam shut. Paint is slowly degrading its ability to accept clear. The product sheet will tell you how soon you can recoat the base and the longer you wait after that time the worse the bond between paint and clear gets until you get to an unacceptable point when the recoat window expires. Sooner is better. When you are all done and find a flaw it is easy to fix later after everything cures.

I would hate to sand on fresh paint and then need to get the whole car squeaky clean again before I was able to put more base and clear on. If you anticipate doing a repair, save it for another time. Just my opinion.

Don’t sand base coat before clear coat. You will see every scratch the paper makes. If you wait too long between base and clear you will need to scuff and apply more base on the entire car before you can clear coat it.


Bob K

[Len]

I'm with Bob, spray your color then spray your clear. Do it all in one spraying session because there's a better chance of success. Waiting too long increases the chance of dirt in the job as well as a decrease in adhesion between the two stages.

[silentdub]

Thanks for the advice from both of you. I will make this my practice.

I read somewhere that is was better to wait a while, but guess I read wrong.


Thanks again!

[SamG]

I'm with the other guys...If circumstances won't allow me to clearcoat the same day, the next day I'll usually spray one more coat of base then wait 30 min before clear. If doing all in one day, I generally wait double the minimum stated time. Gives the basecoat reducers plenty of time to escape.

This is with ChromaBase or Montana basecoats, I cant speak for PPG or other brands.

SG

[MARTINSR]

Ok, let's look at a middle ground here. The recoat window is the outside end of recoat, but the flash time is WAY more critical than waiting out the recoat to end. The manufacturer gives that recoat time because it is safe to paint up until they say it is the recoat limit, period. And what they say is a VERY safe limit. 24 hours means more like 36 but the 24 is PLENTY safe. It's like the old joke about how a Twinkie has an experation date 10 years after production. Guy eating a 10 year and one day old twinkie...."Does this taste ok to you"?

25 hours on a 24 hour window the paint isn't going to fall on the floor.

But shoot your paint before the base has fully flashed say 30 minutes after shooting the paint when the manufacturer says wait an hour and you damn tootin it COULD fall off onto the floor! (ok I'm exaggerating but not by much!)

Leaving it a good long time into that recoat window is always recommended by me. There is NOTHING that creates more failures in painting, NOTHING even close, than trapped solvents!

Letting it flash off a little isn't going to hurt a thing it can only help.

Now, this doesn't mean I would let it set until the next day, I just can't do that, I would be nervous wreck and wouldn't be able to sleep a wink! But leaving it for many hours, I will do it when I can.

Brian

[JCCLARK]

x2!! Brian is right.
Most problems are from not waiting long enough.
Some resto shops wait till the next day to clear basecoat
and will tell you it gives a better job because all the solvents
are out of the base so the clear stays more clear
and has less shrinkage in the future.
24 hrs is fine, done all the time.

[Mooch]

To me it would depend on where you are doing the job . If in a pros paint booth i would give it more time . If in a make shift booth i would tend to not wait too long .

Mooch

[silentdub]

To me it would depend on where you are doing the job . If in a pros paint booth i would give it more time . If in a make shift booth i would tend to not wait too long .

Mooch

That makes perfect sense to me. For those of you that wait a few hours, do you wipe down the base with like a tack cloth prior to spraying clear or so you just spray?

[Len]

That makes perfect sense to me. For those of you that wait a few hours, do you wipe down the base with like a tack cloth prior to spraying clear or so you just spray?

When we spray a car here we usually only have about an hour (at 70 degrees F) between color and clear and we don't touch the color before clearing.