TheSamba.com :: View topic - How long to wait before sanding runs and putting on more?

Mon Oct 19, 2009 1:32 pm

If I have some runs (painted yesterday) How long do I wait before sanding them off and spraying the panel again? I think I can just sand them down and then do a coat or two on teh door and all will be good.

I am just wondering about that first layer drying /shrinkage type issues.

thanks!

Acrylic Urethane single stage paint

Mon Oct 19, 2009 2:39 pm

the can says 16 hours and the spec sheet says 6 hours, i am just wondering what best practices are.

Mon Oct 19, 2009 4:17 pm

usually I will cut the tops of runs/sags the next day with a razor and then 5 to 7 days before I will start to sand. No more than 30 days . It can be done
after 30 but the clear will be harder to work with.
I cut with 800 or 1000 dry with a DA then scuff with ultrafine scotts brite pad
before the next coat

Mon Oct 19, 2009 7:50 pm

wow
let me tell you the truth
within ten minutes
Hit it with 1500 just on the top and keep striking until it is almost flat
then recoat immediately

I just cannot believe this place sometimes

Mon Oct 19, 2009 8:01 pm

JerryMCarter1 wrote: wow
let me tell you the truth
within ten minutes
Hit it with 1500 just on the top and keep striking until it is almost flat
then recoat immediately

I just cannot believe this place sometimes this was very comical...heck i dont need to watch tv for a laugh..i can read stuff like this..

Mon Oct 19, 2009 9:38 pm

BigPaddle, if you look any where in the Body/Paint section, you will see Spook's posts are usually the primer that we use. He's the professional; use his advice.

Tue Oct 20, 2009 4:01 am

spook wrote:
after 30 but the clear will be harder to work with.

BigPaddle
Quote: Acrylic Urethane single stage paint

Spook, are you referring to 2-stage. I believe the op was referring to single stage. Would it be the same?

Tue Oct 20, 2009 4:37 am

my bad, missed that,
If it is a single stage, the enamel-based paints are softer and less durable than urethane.
with that been said
Drying times vary among paints, check the Mgf data sheets of your paint for specific recommendations. Chances are good your paint needs to dry for 12 to 24 hours before sanding begins. most of the time I will cut the surface will 800 or 1000 24 hrs after and let it sit for a week like that. You have to allow for shrink back as it out gasses.If you don't allow for that you will see more roughness.The other danger of not letting it out gas is that the bottom layers of paint will remain softer than the final coat.

Tue Oct 20, 2009 5:44 am

I cheat- i use a heat lamp on the areas to cure out then sand,has worked for about 20+ yrs.

Tue Oct 20, 2009 7:31 am

66 buggie
I have been doing this work for over fifty years , probably painted 600 cars

My guess is that you have never tired it

Let me go through it again
A small run or sag
In ten minutes or so roll the 1500 in your fingers and strike the top of the sag; it will not strike well because it moves
Keep striking all directions until near flat- sometimes a hair dryer not hot !
Repaint
This is single stage - color –Arizona heat

Never ever had a problem

If you want to do everything the manufacturers way, you have to remember they take the safest route It would be dry then probably da sand and then wet block then paint - doesn't have to happen dude

the only thing funny on the thread is your idea of excluding experience, Now that is funny !

Tue Oct 20, 2009 7:33 am

Are you useing PPG spook

Tue Oct 20, 2009 7:34 am

Big paddle
what kind of paint are you useing
what manufacturer
what temp thinner
what is the temp in the garage

Tue Oct 20, 2009 7:35 am

Wed Oct 21, 2009 5:17 pm

JerryMCarter1 wrote: 66 buggie
I have been doing this work for over fifty years , probably painted 600 cars

My guess is that you have never tired it

Let me go through it again
A small run or sag
In ten minutes or so roll the 1500 in your fingers and strike the top of the sag; it will not strike well because it moves
Keep striking all directions until near flat- sometimes a hair dryer not hot !
Repaint
This is single stage - color –Arizona heat yea

Never ever had a problem

If you want to do everything the manufacturers way, you have to remember they take the safest route It would be dry then probably da sand and then wet block then paint - doesn't have to happen dude

the only thing funny on the thread is your idea of excluding experience, Now that is funny ! yea go figure old timer...u need to update ur techniques...laquer days are over my man ...600 cars ..i got ya beat on that my friend..nowadays we use spray guns not the ones u pump.Almost forgot having 6 cars in magazines that i did.I dont strike a run i sand it .Never seen the hammer technique (strike the run)..post a vid so we can see plz.

Sun Aug 22, 2010 1:47 pm

All posturing aside, I did a fender today with single stage enamel. It's been sitting in direct South Texas sun for about 3 hours, after having sat in the shade for about 2 hours prior to that.

How long before I can sand it?

Should I wet sand it?

What grit?

I'm not trying to get it super shiny, as the rest of the car's paint is old and tired and I don't want it to stick out like a sore thumb.

Thank you for your time, consideration, and advice.

Sun Aug 22, 2010 3:21 pm

i work at a custom paint shop as lead painter, and with single stage, if i need to re-spray, i wait 8 hours to cure, sand with 400 to 600 then reshoot 1-2 coats. if you use the same paint you should see no difference. if its a small enough run and a solid color, you can use a nib file to cut it down, sand it with 1000 grit then 1500 and use your standard buffing process to finish.
finally when you are sanding out the run, sand it out and then some more!
you will see shadows of the run if you dont take it down enough.

and as for shrinking, if you just shot the fender, and you sand out and re-shoot in 8-24 hours it will just be like your adding coats and it will all shrink together..no worrys!
hope this helps

Sun Aug 22, 2010 3:24 pm

oh yeah....you can sand it dry after 8 hours.....
(sometimes wet sanding works well when paint is still green...so it wont ball up and always used on color sanding....but you dont need to do that in this case.)

Mon Aug 23, 2010 10:16 am

Thank you