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bigbrowndog 04-13-2006 10:37 PM

Couple of base coat/clear coat questions
 
A few quick questions for a PPG base/clear coat job:

1) Paint shop said since we are using the low end of PPG's product line, it may take 3 coats to cover. Said to wait 15 minutes between coats. Agree? Temp this weekend will be in the 70s.

2) Runs -Paint shop said to use 1200 grit and sand out any runs between coats. Agree?

3) Clear - How many coats of clear would folks recommend? Do you sand between these? And if not, how long do you wait to put on a second or third coat?


If there is anything else you would recommend we keep in mind, let us know. We are shooting on Saturday. We don't expect it to be perfect, but expect to learn a lot doing it..

Thanks

Ty

milo 04-14-2006 12:12 AM

.
Different base systems act different ...
.
.
thats why there different
,
,
what EXACTLY are ya gonna use ? :rolleyes:

302 Z28 04-14-2006 08:31 AM

The time between base coats depends on the reducer he is using and the current temp. Refer to the paint "P" sheet for guidelines. You can wait as much as 24 hours between DBC base coats before you must scuff the surface before re coating. The main thing to remember is give the base plenty of time to "off gas" the reducer. Three coats is considered minimum to get good coverage and is the norm. Three to four good coats of clear is also the norm. you cannot do any spot sanding on on the final coat of base before applying the clear especially if you are using metallics.

Vince

bigbrowndog 04-14-2006 10:00 AM

Follow up
 
We are using OMNI AU MBC base coat, their "fast" reducer and their clear. We have 22 percent humidity and I am painting in "thin" air at about 7500 feet above sea level. Sheet from PPG says 5 - 10 minutes between base coats at 70 degrees. Should I wait longer or do folks think it will flash quickly.



I bought a new Devilbiss FLG-653G-13 FinishLine 3 HVLP gun with 3 tips. Sheet calls for 1.3-1.5 mm tip. Is there any suggestion on which tip may work best for the base coat? Should I go smaller for the clear coat?

For the clear, it says 20 minutes minimum, 24 hours maxiumum under "air dry". I assume this means time between coats, but if it is more than 24 hours, would need to rescuff?

Says 7-10 psi at the air cap. This is the first time I have painted with an HVLP gun. Any pointers on air pressure?

Thanks for your help.

Ty

Dewcat 05-08-2006 01:23 PM

i have been painting for years but just got back into it. I have been old school to ac enamel and top coated clear. Now I have used base c,cc for a year still learning. Questions I have a door on a car that turned out like glass but right near the chrome piece of a 1957 olds super 88 is a 1/4 inch where i ran out of paint believe me i used a gallon of sprayable matierals on this car 2 tone red white and run out of paint on both colors and the door had a spot not covered didnt see it till i cleared the car with 3 coats. The car is now 2-1/2 days cured what can i do about the light painted door. thanks!

Dewcat 05-08-2006 01:26 PM

By the way this bc/cc is a painters dream but i may want to color sand and buff if someone can give me a post as to where to find it or short term it here if its ok thanks.

Bee4Me 05-08-2006 10:04 PM

The Omni MBC I've shot does dry fast but it may be too fast with that reducer.
I'd opt for Medium with those conditions and it will still dry quick
You'll probably need to tack the car after each coat drys as you'll have some overspray and painting over it will be bad news.
Waiting an hour between coats is no problem,makes for a long day but your assured it's dry before the next coat,not that you need to wait this long but FYI.
Sanding out runs or dust nibs is fine but you will need to dust some more base over those areas. 1200 is kinda light for a run IMO, I use some 600-800 wet and clean well after. Like Vince stated,you will have to repaint any metallic sanded. You can try dusting some base and blending it out but it usually ends up being another coat.

Omni used to be a 1:1 so you should end up with 2 gal sprayable out of 1 gal of paint. I don't know what or what all your painting but for just the outside,you'll have plenty, Jambs,trunk,hood,fenders,Nope not for 3 coats.

Clear,20 min recoat is just that, "Should" be ready for another coat in 20 but that is subject just like base to be longer.No scuffing required.
24 hr,is basic complete dry time to buff or sand for recoating. Again, subject to change.It may take longer for the clear to dry enough to sand or buff.
Try some 1500 dry and if it balls or gums up, it's still green.
I would not apply more than 3 coats of clear at one setting. That should be plenty. If it's looking rough after 2,stop and let it dry overnight or the 24 hr. and color sand it with 600-800 and reshoot it after you figure out "why" it looked so bad. You'll either o'peel the snot out of it or dry spray it.


As for tip size. I prefer a 1.4 for either base or clear. Choose between a 1.3 or 1.5. I'd go 1.3. You'll need to do a lot of test patterns to get the gun/air right.
You "generally" run about 10# more for clear.

GRN69CHV 05-11-2006 06:45 PM

I just shot OMNI MBC and 161 clear today. Used MR186 reducer. Base flashed real fast. Had a couple of spot repairs in the first coat of base to take care of, it was dry in about 30 mnutes to sand 600 wet. I did not tack in between coats, but did tack after base. In order to get the clear "wet" had t really lay on a 3rd coat - it ran in spots. P-sheet recommends 2 coats. If had to do it again, I would shoot 2 coats clear, let cure, sand with 600-800, then 2 more coats clear, then 1000, 1500 and buff. A it stands, sanding is inevitable, but I doubt you will be able to snad in between clear coats if it is done in one day - just not enough time for the clear to harden sufficient.

Dewcat 05-12-2006 03:58 PM

I dont know much about ppg, but i use medium to slow reducer for the clear and the last coat use SLOW reducer so it dont flash so quickly if it does you chase your dry spots and its a race you dont have to run_ no pun on run.

GRN69CHV 05-13-2006 05:04 PM

A little added info. I shot 3 coats of MBC base - color is '69 Frost Green Metallic (code 59). Shot over grey primer. It really covered in 2 coats, I shot the 3rd for safety. Gave it 3 coats of clear and have now sanded out the runs in the clearcoat - wasn't happy with the clear. Have a couple spots to touch up and will give it 1 color coat overall, then re-clear. So far I ahev only used 2 quarts - bought total of 5 to start.

Dewcat 05-13-2006 05:17 PM

So many factors figure in, the temp and humidity, the length of time between base coats if you apply to soon you trap your solvents and especially metallic its tough but doesnt sound like any zebra stripes so thats good. Hang in there it gets better with practice becomes expensive on matierals but that happens in almost anything we do. goodluck. :)

MetalDrgn 10-14-2007 11:48 PM

You can see when the base coat flashes because it goes from semi-glossy to flat once it has flashed. Omni MBC calls for 2-4 coats. Some colors like bright red might require more coats because it is more transparent than something like black. Also unless you are in a cold place, I wouldn't recommend a fast reducer. a slow is what you need in 70+ weather. My flash times in 80F, high humidity weather are about 8-12 mins. sometimes faster.

I see some of you spraying 3 coats of clear. Omni AU clear calls for 2. no more no less. Too heavy of a coat will sag and too little will make it bumpy because there's not enough material on the surface to join the droplets. I usually wait about 15 mins or so before applying the second coat seeing how you can't really tell by looking. you can touch it if you want to see if it's tacky, but your fingerprint will be in that clear permanently.

I use a satajet 1.3 for the base and 1.5 for the clear. I also seem to be able to get away with spraying primer with the 1.5 tip as well, but I would recommend 1.6-1.8.

Unless you get runs, I wouldn't sand after the primer (320-600grit). If you do get runs, depending on how transparent the color, you might have to go all the way back to the primer and start over. I've tried color sanding with 1000grit and after clearing, you really can't tell the difference plus like others mentioned, if you are using a metalic or pearl coat, you can't sand it prior to clearing it.

If you are not familiar with spray painting try it out on a test hood or panel if you have any spares or get one at a junk yard and section it off for more than 1 attempt. btw, be careful when applying clear with tape above the area you are clearing because the clear runs off the tape easy. Try and just mask it off with paper stretched at the ends with tape. that's if you are painting vertically though. I'm not sure what would happen if you had the part flat on the ground. (wow I did a google search and found this thread and didn't realize how old it was. but I hope it still helps someone out there)

ldclark1 11-04-2010 11:35 AM

Omni painting
 
follow the the tech sheet as closely as possible. Waiting time between coats of any paint is the secret. Don't be in a hurry. Don't color sand the basecoat unless you want streaks and unless you wait a day between clearcoats you should not sand the clear. If you've messed up, your option is to let the clear dry, sand and recoat with clear after it has dried. Don't sand into the basecoat unless you want to start over from the start.
This comes from years and years of painting from enamels to b/c.

Hotbo 11-04-2010 12:31 PM

i didn't catch what Omni clear you were using?

if it was me i would use a slower reducer.

i would use the MR187 it says slow but is faster than what you think

wait 15-20 minutes in between coats

why would you get runs in the BC????

if so wait a hour and sand them out with 1000 grit.

clear if you are using the mc161 HS it mixes 2-1 and doesn't lay real good imo

put at least 3 coats and wait 15-20 minutes in between coats.

use the clear coat MH168 Hardener it says slow but its not,perfect for the temp and a all over.




hope this helps,Travis


PS take your time in between coats of base and clear you will a ton of better results :thumbup:

Irelands child 11-04-2010 04:14 PM

Guys - this thread is 4-1/2 years old. I hope he got his vehicle painted successfully by now :sweat:

(and you aren't the only ones to dig up ancient history :embarrass )


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