Sanding ?

[TBK1]

in process of body repair and sanding, on the places (paint) that are not going to be taken down to bare metal do you just need to break the glaze or shinny coat of paint, using 120m and 220 grit. and what do I need for final grit before paint (400). plan on using a sealer, then base color then clear coat.

This is 411 sunburst yellow, am using light grey primer on the repair areas, do I have to use the same on ALL of the body to achieve a uniform color at the end or can I just leave the unrepaired areas yellow and just primer the repaired areas?

Also the hatch and fenders are a dark brown I assume I need to gray primer those entire items for uniform colr to match the rest of the body.

Car has been painted before and looks like it is still adheareing very well except around the body rubber/gaskets which are now removed and those areas will be taken down to bare metal and featherd in smooth.

[BD240Z]

Donald,

I've painted two cars in my life, both in my garage and both turned out pretty nice. Here's my feedback.

If you feel the existing paint is sticking well to the body, that paint can be wet sanded with the proper grit and then primered/painted over top of.

I don't think your primers need to be the same color provided you spray a uniform/thickness of paint. However, different colors of primer may trick your eyes into thinking you have thin areas and you'll paint more in those areas. I recommend that since you've gone through all the work and expense of prepping your car for paint that you primer the whole car with the same primer and primer color.

I'd be more concerned that ALL of your painting supplies would work together as a team. I believe that the sealer, primer, base and clear coats should all be from the same manufacturer. I've been told not to mix materials from different manufacturers.

Sanding grits should be called out on the Tech Sheet from the appropriate manufacturer. Use those to determine how to prep the surface as well as your mixing ratios and cure times. I got a lot of advice from the paint supply house where I bought my materials

Others here are much more experienced with painting cars, hopefully they'll post their thoughts. Good luck with your efforts, lets see some pictures of your car when finished.

Bruce

[jmark]

TBK1,

Is Shane painting the car?

[EScanlon]

Don;

There's been several threads started and discussed at length on this. Not trying to give you the "Do a search" routine answer, but there is a LOT of material that has been discussed.

If what you want a short, nitty gritty, "Earl Scheib" type of answer, i.e. the Cliff's notes version:

Taking the paint "down to the metal" is only necessary if the existing paint AND primer is bad OR if you have the time and money to do a paint job like they show you on "American Hot Rod".

Don't wet-sand to or around bare metal if you don't absolutely have to. You're asking for more problems on a number of levels.

Use a D/A sander with 220 over the complete car to SMOOTH the existing paint and reduce it's thickness. In the process you'll be leaving 220 size scratch marks which are sufficiently coarse enough to apply your fill primer on top of.

Filler primer is used to build up the panel to further SMOOTH the body panel via sanding. Fill primer is generally applied OVER etching primer.

ETCHING primer should be used wherever you have bare metal. A metal etching solution as a prior step to the etching primer is usually not necessary, but not necessarily a bad idea. However, note that SOME etching primers will NOT work well on top of previously etched metal. The key is to know that it will work with the materials you are using afterwards.

PPG sells a wonderful metal etcher, which will work very well with their epoxy primer, or their fill primer, or the various brands of polyester body filler. However, it will cause major problems with lead-free solder's tinning solution (required to make the solder adhere well), or with another brand of epoxy primer. So the bottom line there is to know what you're working with and what you will be putting on top to make sure everything will work together.

There are has been a ton of discussion regarding whether you should do body-work on bare metal, or on etch primered metal. I'm referring to plastic body filler. Both sides of the discussion make good points...YOU decide what you want to do.

Let worked plastic body filler cure for as long as possible before you primer / seal over it. This means you apply it, you shape it, and you smooth it, then you let it sit either under infra-red lamps to help de-gas it or you wait several hours / days (again, many different schools of thought). This is to ensure that you don't trap any solvents that should have evaporated AND to ensure that shrinkage AFTER you've applied paint is minimal and hopefully unnoticeable. Your final smoothing on bodywork will range between 220 to 280 or 320 sanding paper, which still leaves some "tooth" for the fill primer to bond to.

Most bodymen will advise doing a full fill primer coat or two on top of any body work to make sure you have a fully smooth surface without having to rely much on glazing putty. (Red Cap or "Icing" body filler) Your final sanding on the fill primer will be with 400 grit. Again, this still leaves enough tooth for the SEALER to adhere to.

Definitely allow glazing putty to cure before you sand it, and let it cure AGAIN afterwards. (See the shrinking problems above.)

Use a SEALER on top of all this. This is the final coat over the WHOLE car to ensure compatibility between the base coat of paint and the surfacing compounds already on the car. This also provides a uniform color base to enhance the paint from the first coat out. Generally, most sealers are NON-SANDING..as long as you stay within the time guidelines provided by the manufacturer. Wait too long and you WILL have to sand, don't wait long enough and you'll have problems. READ the sealer material's tech sheet.

As pointed out by Bruce, you won't be over-painting to achieve the same color. The money you save by not sealing the whole car is very poor economy when you consider you could run / sag / orange-peel / craze / blush / crack a paint job by uneven paint spray. Again, READ the paint material's tech sheet.

2¢

E

[Maddos]

I would say absolutely have the same colour undercoat all over especially with a yellow top colour. One of the yellow submarines I work on had a respray with only the damaged paint getting a hit with primer. End result was a sub that looked like a spotted cow.

[TBK1]

Thanks for all the info, think I got what I needed.

Jmark, not this one, think I,m gonna try this one myself, dont wanna get alot of labor dollars tied up in it and hell I cant do worse than the first JA that painted the blue one (not shane).

[CANDYBLUE2+2]

I wanted to make sure that I was reading this thread correctly. The whole car will be yellow? If so, don't do what so many before you have done and ended up regretting. Ever seen a yellow paint job that had what I call "Green Spots"? Thats what you get with yellow over either the unprimed areas, or the primed areas, depending upon the sealer coat or lack of a sealer coat. Confused? You should be...Do what I do, and I guarantee you will love the results.Yellow is a pisser of a color to spray evenly without the help of a white ground color.That's right...spray a coat or two of white base, just like you would if you were painting the car white, let that dry a good bit, enough to be able to run a basecoat tac rag over it, then follow up with your yellow and watch how much easier it will be for you to achieve the best yellow finish in town! Good Luck and happy spraying!!!

[EScanlon]

Excellent point!

Too often inexperienced painters forget that the BASE paint's color is Primer/Sealer color.....then followed by the COLOR paint of your favorite hue and effect; and then the CLEAR paint.

The Base paint's color will definitely affect how THICK the next coat has to be before it evens out in color.

As John pointed out, yellow paint is very much translucent to a degree and it will pick up the differences in the base it is applied onto. Paint red oxide primer and see how many coats of paint you have to apply before it LOOKS yellow.

So use White Sealer over your primer and you'll not need to get more paint, just make sure the sealer you use is white.

Good point John!

E

[TBK1]

ok lets see if I understand this right, do my sanding and bodywork, prime where needed, then sand to 400 grit, seal with a white color sealer, tack rag it, spray my yellow base coat, tak rag it, then spray clear and do the wet sanding then buff/polish!!!!

[CANDYBLUE2+2]

Just a second. The type of sealer you use may not be wipeable with a tac rag. Some tinted sealers will dry quick and can be wiped accordingly, while others will remain a wee bit tacky and should not be touched. Find out from your paint jobber what youv'e got and wether tacing it off is adviseable. Everything else you said sounds like your ready to give it hell,,,Go For It...John

[EScanlon]

...snip...Some tinted sealers will dry quick and can be wiped accordingly, while others will remain a wee bit tacky and should not be touched. Find out from your paint jobber what youv'e got and whether tacking it off is adviseable....snip...

...snip...I'd be more concerned that ALL of your painting supplies would work together as a team. I believe that the sealer, primer, base and clear coats should all be from the same manufacturer. I've been told not to mix materials from different manufacturers.

The bold highlights the important points here.

John's point is dead on...Want to find out the hard way? Go ahead and tack and see if you don't end up with fish-eye's , crazing, the lint that the tack rag had picked up before sticking to your fresh sealer...Get the picture?

But Bruce's point earlier is also right on the money, Spot On as our Aussie friends would say. "Find out from the paint jobber" is more than "Should I use sealer?", it's more along the lines of "Do you have the technical sheets on these products?". While it may seem pedantic, or even "snobbish", what you're trying to find out is process times, methods, and most importantly....compatibility.

The majority of products you are working with have certain windows of time within which you can do certain processes, and outside of those windows (and depending whether before or after the window elapses) whether you can do the process at all.

As an explanation, most primer/sealers I've worked with recently are of the NON-Sanding variety. That is, you don't NEED to sand it before you apply the next coat of paint. However, there is a distinct time window of opportunity. You can't do it before the window opens, and if you wait till the window closes, now you MUST sand in order to get the next coat of paint to adhere properly. There are certain Do's and Don't Do's within that time period. No sanding can also mean no tack-rag, or don't cover or lay anything on the surface or even handle at all. While some sealers are very forgiving, others are very touchy....to find out what you have, you read the tech sheet.

Good points John and Bruce!

E

[TBK1]

thanks guys, I've learned a bunch here!