Painting/Finishing 101 (1 Viewer)

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Joined
Feb 21, 2009
Threads
170
Messages
1,009
Location
Enumclaw, WA
I will pick up where this post left off. I was about to start describing a few primering systems when I chickened out, but am gonna 'splain starting there.

The first thing to remember about painting is that every thing you do will shape the final finish. No matter how unimportant a step might seem, I can guarantee you that not using proper blocks and techniques can leave bold scratches, flat spots, finger lines and other unprofessional imperfections in the finished product.

Before you start any work towards painting your car, you need to decide on a paint system to use, and a method. I prefer the collision method unless the car to be painted will be a show car that will be scrutinized by 1000's of people at shows. (You know the type of person... There is always that one moron who walks around a car show and tries to find flaws in all the cars at the show. People think they are some sort of almighty when they find that one dust nib or whatever.)
The preferred method for a show car is to strip the car to bare metal by whatever means you wish, then cover the car in a self etching, then an epoxy, then a build primer, and finally a sealer before paint.
The collision repair method of choice (with flat rate shops) is to do the nessesary repairs, cover the bare metal and filler with a direct to metal building primer, and then paint over top of the primer. (see the time difference potential between the 2 methods?)

First, I will outline how to use these direct-to-metal building primers.
I use mainly PPG paint systems, but have used others in the past, I just prefer the PPG. After all bodywork is done, and everything is feathered out, and all scratches made with <150 grit are feathered out with 150-220. You must scuff up the remaining part of the area to be primered using anything from 150-360 or a red scotch brite pad. I use red scotch brite pads and scuff everything that might get primered. This will ensure proper adhesion. on plastic parts, I use Bulldog adhesion promoter, and then primer...

If you were doing the whole car, all you would have to do is mask off any areas where you don't want the primer, and then prepsol the entire area to be primered. Wipe on-wipe off, or spray on-wipe off... thinner based or water based, but water based prepsol shouldn't be used directly on bare metal.
At this time, you are ready to mix your primer. Using PPG, you would select something like NCP-271 or NCP-270 depending on color red or gray. NCP is mixed 3:1:0.5 NCP:NCX:DT primer:catalyst:reducer I don't reduce my primer unless I am going to do 3 applications, I will use it on my 3rd application. After the primer is mixed, do not let it set for an induction period, as it will dry very rapidly. immediately into the gun, adn put down a very thin coat, almost a spattering, so that you will reduce the chance of fish-eye condition. The second coat should be started immediately after the light first coating. After the second coat(1st full coat) wait 15 mins before starting the 3rd coat. Then repeat for the 4th coat. That will give you 3 full coats of primer.

Once the primer has cured(refer to the TDS) leave the thing masked off and apply a guide coat. a guide coat (if you don't have guide coat paint, shoudl be done with a flat black lacquer paint. You can get that at a dollar store for $1 a can. Just hold the can 12 or 24 inches from the surface and mist it just enough so that the surface is black and speckled. This will enable you to see what you are sanding later. Once the guidecoat has dried, you can begin sanding. If the car will be somewhat of a show car or if the bodywork is questionable, you can start with 150 grit dry, leaving the car masked off. With long hard rubber blocks and 150 board paper, begin sanding with the longest blocks possible for the area being sanded. for example, if you are on a hood, you can use a 16" or 9" block, and sand in all directions, to ensure that you will not have any ripples, since the hood will be veiwed from all angles. on doors, fender sides, and 1/4 panels, you are best to sand only along the body front to back, or if there is a curve to the panel, hold the block facing the front of the vehicle, and sand down and away without twisting the block. You pattern shoudl resemble this "/////" if that makes sense. that way, you wont sand flat spots into the curve of the panel, but at the same time will knock out any ripples along the sides of the vehicle. You just have to sand until the guidecoat is completely gone. Fewer strokes should be nessessary along edges and corners. Try not to bite through. If you find you are biting through a lot, you might have high spots, or large dents still present. adding extra icing may be necessary, as might some hammer blows. let the block and the guide coat show you where you need more work. This will give you a good start to building your primer. Now the car (remember you left it masked off) is ready for a second application of primer. Primer it as you did the first time, prepsol and then apply 4 more coats, then a guide coat. at this point, if you are fairly sure you have gotten the thing straight, you can unmask and start wetsanding. If not, you can continue with 150 grit and block the car down dry again. Just remember, you have to reapply primer after blocking with 150 dry.

WETSANDING YAY!

before wetsanding, you need your water buckets, a few sponges or rags, and preferably a garden hose if possible. You will need 400 and 600 grit wet0dry paper. Begin by soaking your paper in the water bucket so that the back of the paper gets soft. The paper acts kind of like a chamois, in that after it gets wet it will absorb water. Start sanding with 400 grit paper to knock out the heavy orange peel. For 400 grit sanding, I use everything including the kitchen counter for a block. I use my 3M hard rubber sanding blocks, dura-blocks(careful as the older they get, they more warped they get) 3M wetodry squeegees, Formica counter top cut and planed, and pieces of machined aluminum. I have seen some people use No. 20 foam sponges, but, they seem kinda soft to me. Sand in the same way you did with the 150 dry. just keep the surface wet, and the paper wet, dipping it in the water bucket every couple of strokes. This will keep the paper clean, and the primer clean. Every once in a while, I will hose down the spot I am working on, and then dry it up with a rubber squeegee to see if any more guide coat can still be seen. It's easiest to work from the top down, change yoru paper often, and go slow. There might be some spots where it seems the guide coat just doesn't want to sand off easily. Well, don't be alarmed, it's probably not clogged paper, but rather a low spot. You can always add that 3rd or 4th or 5th application of primer
crazy.gif

After everything is done with 400, this is the time to assess the finish. You may find that another application of primer is necessary for lows spots or spots where you cut through the primer. stop here adn mask off the car again. This time, do 4 more coats, but add that DT urethane reducer to your primer. That way, it will go on a little thinner, and with less orange peel. guidecoat again... then wet sand again with 400 grit. IF everything looks perfect, and smooth adn flat, and most importantly FEELS SMOOTH AND FLAT. you can dry it out reguidecoat it, and wet sand in the same manner with 600 grit paper. This will give you the final sanded finish for paint.

You can look down the side of the car and seea reflection in the primer at this point. This will give away any ripples or imperfections, and depending on how picky you want to get, you can fix them by applying more primer or filler and continue to sand. At this point, you will realize why paint jobs cost so much money.
grin.gif
...so will your hands and back and knees...

you can continue from here with final masking, and then finally, after everything is masked off, prepsol everything once again, and then blow off the surface with hi pressure air, and wipe at the same time. this will free dust and remove it form teh surface. just remember to let the air settle in teh shop before you begin sprayin paint (unless you are in a booth. If you don't have a booth, you can make one out of any normal garage. all you need is a bunch of furnace filters (enough to put in a few windows of the shop) and a few old box fans. open the garage door enough so you can slide the fans under and pull the door closed on top of the fans. fill the extra space aroudn the fans with cardboard or dead raccoons or whatever you have laying around, and put the filters in the windows, then crank the heat up in the garage. I see a lot of people putting their fans up high, well, that defeats the downdraft effect. You want yoru air to enter high and exit low. if it is cold outside, this will counter the way you want your air to flow so more fans will be needed.

tada! ...homemade paint booth.

That takes us to final paint.

Which will be covered next time.


Here is the alternative way (older way) to do a show car finish.

Many people have different opinions on the best way to primer a car and what, so I will elaborate a little more on the longer route to paint. (here's why you won't see a collision shop doing this to all wrecks)

First step: covering bare metal.

Bare metal needs to be etched properly for adhesion and corrosion resistance. THe best way to get metal ready is first to prep it with prepsol and then apply a self etching type primer. The best one I have seen to date is made by Martin-Senior. "Vinyl Wash" primer is a special type primer which will etch the metal and make it ready for just about any type of epoxy primer. VW is extremely resistant to corrosion and is very water resistant. I have heard, but not directly from, the ARMY, NAVY and AIR FORCE uses this type of primer underneath all OD green paint and we all know how those vehicles sit outside 24-7 or in the water all the time. They never look rusty...
All you need is 2 light coats of VW primer over top of prepped metal. The nice thin about it is, you can leave bare metal for years in this primer and not have to worry about it. when you get around to top-coating it, all that is necessary is a quick coat over top of it, with no scuffing to re-wet it, and then it is ready. It's also transparent so you can cover everything with it, and be able to see the steel underneath, in case you need to do some metal work, or rust removal. This is not recommended to be put over top of any kind of paint or body filler. A little over-spray won't hurt anything, but gobbing it on isn't' advised.

You need not apply this type of primer to any painted areas. if you didn't strip yrou car to bare metal all over, you can just spot it in with this stuff. This primer is just for spots of bare metal.

now you are ready for your epoxy primer.

Second Step: Epoxy primer for sealing.
Some epoxy primers are both self etching and epoxy primers, which would eliminate the first step. Epoxy primer is necessary to have on top of bare metal and bodywork to seal everything from water (wetsanding). I prefer to use Matrix epoxy primers because they are self etching. Specifically MP-480. You might have heard of DP-50, which you can't buy anymore. It is now only sold as DP-50LF which is lead free(crap, absolute garbage, not worth buying) THe worse it is for your body and the environment, the better it will protect your car. remember that. MAtrix is a copycat company that takes all of PPG's patented formulas and recreates them as the patents expire. So when you buy MP-480, you are actually buying DP-50. so, you mix it 4:1:2 primer:activator:reducer and then after stirring let it sit in the mixing cup for 30 minutes. This is called an induction period and will let the activator do its' thing and let everything start to work before applying. This stuff is extremely toxic and deadly, so don't drink it, no matter how much you like the taste or smell. Don't feed it to raccoons either (unless you run out of cardboard to block off the bottom of the door near your fan).
after letting it sit, dump it in the gun (oh and always strain everything. you never know when you might end up with a piece of stir stick or a lump in it to plug your gun.) Apply a first light coat to avoid the fish eyes, and then put 2 full coats on. I can't remember off hand but I think you must wait about 6 hours before top-coating this stuff, but no more than 1 week. After the week, you need to scuff it up before applying anything over top of it.

this brings us to...

Third Step: Build Coat Primer

This is the primer you will do all your sanding on. You can get either K36 or 2K or whatever else you want to get, as long as it is approved as a topcoat for the epoxy primer you put on before it. check the TDS. Mix it up (can't remember the ratios) and strain and then apply over-top of your epoxy primer within the time window in the same manner as the epoxy. There is no induction period though. apply a light coat, followed by a heavy coat, and then after 15 mins of flash time, apply a 3rd coat, wait 15 and then a 4th coat.

then guide-coat and follow the directions above for sanding.

...


(I'll assume you've gone back up to the top and read through until the final paint part, and have everything ready to go for final paint)

Fourth Step: Sealer Coat


Now, you should be completely ready to dump your paint in the gun and start shooting, but wait, you need to seal everything since that build primer likes to take on water. All you need to do is mix up some sealer. I used the same MP-480 in step 2. If you mix it 4:1:2(I think the can says 4:1:0.5 but I could be wrong), you can use it as a sealer overtop of the build primer. mix up the primer and strain and then apply a very light mist over top of everything. then apply one medium coat over top of build primer. The sealer should be even and as perfect as your final coat of clear or SS paint. sometimes you have to go back over thin spots wiht a quick fast shot and even things out. if you mess up there is redemption, but it is in the form of sanding with 600 grit after waiting 24-48 hours for it to dry. as long as you don't break through the surface, you can conitue to put your final paint over-top of the sanded sealer, but applying another sealer coat might be the only way to go to keep everything even.

Check the TDS to see if you need to scuff everything or if you can put sealer overtop of the sealer with in this time window without scuffing.

and that's the long way...
 
Last edited:
Your hands must hurt from typing. Lots of good info, but you must have worked at some shops that didn't mind spending thousands and thousands on materials. You add alot of steps that I would consider unnecesary if you've been doing autobody long enough. I am a firm believer of blocking/using guide coats etc. the ever living sh#t out of a panel/vehicle etc. before being remotely ready for paint, but I would never wet sand primer until I'm ready to paint. You recommend wet sanding and then respraying primer which seems a little confusing to me. As for etching primers, they seem to be becoming a thing of the past. Epoxy is a much more superior type product not only because of its adhesion qualities, but it is way more compatable with other 2k primers and urethane topcoats. It will also accept body fillers and high build primers without sanding as long as its done in it's pot life. Much more user friendly to me. It is suited, along with recommended, to be used over bare metal. Sealer is another step which receives alot of debate in the autobody field. I personally don't use it because I use tintable 2k primers which act just like a sealer. The less paint cans I have on my shelves the better. Paint companies are in the business to make money, so the more products they can stock your shelves with the better off they are.

Not trying to bash your thread at all. You're obviously no stranger to autobody. Just letting people know some of the short cuts when trying it on there own. Besides my fingers are starting to hurt from typing.
 
Danno:

Great write up, quit making us wait and post up the final chapter!

I personally don't use it because I use tintable 2k primers which act just like a sealer.

I'm glad you posted that; someone had told me that you didn't need a separate sealer between a 2k high-build primer and an enamel (AE) topcoat, and I've been wondering if that was true. So much of this is a mystery to us beginners!

Brian
 
i agree w/toomanytoyz. i think u do a good service here but u need to let the newbs know that this is not the only method available. first off, alot of epoxies i have used can't be applied over etchers. it can actually cut down on adhesion. second is the fact, that if u're having to lay down 4 or 5 coats of primer, u're bodyman sucks. primer is not made to repair dents, it's made to fill LIGHT scratches & smooth the transition between the filler & featheredge. at work, we finish filler w/120 followed by a light brushing w/180. featheredge w/180 & have the painter lay down 2 coats of k36. if he blocks thru before the guide coat is gone, u get wrote up, bottom line. this method increass production time & saves a buttload in material costs which i'm pretty sure would be appreciated by most everyone here.
 
Wow..awesome write up..no steps skipped..I'm going to print that and hang it in the shop in plastic!!!

Just a side note on the Bulldog..have you found it to have a bit more texture than say a single stage enamel? I do most of my spraying with an HVLP unit, and maybe I should have downsized the tip to something smaller to assist atomazation. I dont think it could have been thinned anymore..hell..it's like water already!!

Good job and thanking you for sharing your vast knowledge and talents :clap::beer::clap:

Pat
 
I did this so others here that have so many questions about it can get a quick reference to use. I agree that there are many ways to cut corners but the vehicle's paint is only as good as the prep prior to shooting color. ;)
 
like i said. i think u are providing a great service to the new guys but they need to know that cutting material costs doesn't necessarily mean cutting corners.
 
I'll be doing a final posting in the coming weeks on wet sanding my rig now that it is painted with pics. My only hesitation is that I don't think you will be able to see the sheen on the panels that you need to understand when the time is right to stop wet sanding the area.
 
I'll be doing a final posting in the coming weeks on wet sanding my rig now that it is painted with pics. My only hesitation is that I don't think you will be able to see the sheen on the panels that you need to understand when the time is right to stop wet sanding the area.

Looking forward to it!
 
Wow..awesome write up..no steps skipped..I'm going to print that and hang it in the shop in plastic!!!

Just a side note on the Bulldog..have you found it to have a bit more texture than say a single stage enamel? I do most of my spraying with an HVLP unit, and maybe I should have downsized the tip to something smaller to assist atomazation. I dont think it could have been thinned anymore..hell..it's like water already!!

Good job and thanking you for sharing your vast knowledge and talents :clap::beer::clap:

Pat

Assuming you've properly reduced the paint, texture is a feature of application, not product. Many things can cause texture in a paint job, but it's commonly either the wrong air pressure, under reduced color, or dry application. Practice makes perfect, and practice is expensive these days. You definitely want to practice on a spare panel or two before undertaking an entire vehicle. Personally, I'm old school and have not learned to love hvlp. Lots of painters use it everyday, and it can work fine, just not for me.
 
was that a book or a post! it took me lot of time to cover it up1 anyways great writting
 
About The Writer

This writer is a professional person in painting job.
If it is possible, will you come to Indonesia? to help me to do the painting.

Hahahahhahaaa......

Congrats...
 
A couple things I learned the hard way when I decided without any previous painting experience, to paint my FJ40 a few years ago:

Practice moving around the vehicle with the hose and gun. You'd be surprised how quickly your back and forearms get tired carrying the gun around, moving it smoothly and all the while managing the hose.

Get a real rubber air hose. The PVC bright colored cheapo hoses at home depot are nearly guaranteed to hit your freshly laid down paint as you are moving around the vehicle. They just dont seem to relax and lay on the floor as well...

Spent alot of time dialing in the air pressure and spray pattern, and the paint consistency!!! This is what makes or breaks the top coat!!!!! Pattern needs to be the stretched oval, and I found with almost all topcoats, that you need a warmer reducer(yes, there are different temp reducers) and more air pressure than the P sheet recommends to get the paint to flow out well, and not solvent pop. They intentionally underrate the needed specs to squeeze into the max VOC's requirements...

Get a piece of sheetmetal, an old door for example. prime and sand, so you can lay a few practice coats down. Testing out on cardboard, while tempting, doesnt indicate how the paint will flow out on your sanded primer on the truck. Look carefully for solvent pop as its drying, and deal accordingly. Orangepeel? Two things: more air pressure and thinner paint(more reducer). experiment.

Some sort of filter/dryer unit is absolutely mandatory. If you dont want to spend the $100 or so on something as simple as this, just go buy spray cans. Seriously. you will have fisheyes. I used a motorguard m-30 which is not ideal by any means but did a good job. Open it up after each paint session and let dry. you'll be surprised at how much moisture will be in there.
 
Orangepeel? Two things: more air pressure and thinner paint(more reducer). experiment.

Orangepeel is a necessary evil when you don't have a booth with an oven to bake the paint on. Reducing/upping the air pressure will usually land you with runs which are much more of a PITA to remove during wet sanding than orangepeel. This is especially true if you are just learning to paint. Besides, a "normal" amount of orangepeel acts almost like a guide coat when wetsanding.
 
Last edited:

Users who are viewing this thread

Back
Top Bottom