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Old 02-18-2008, 07:11 PM   #1
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Default Step by step instruction post about painting.

What we need is a comprehensive step by step instruction post about painting.

Writen and posted for complete paint novices like myself ( and it seems a few others on here).

What'* the advantage of the HVLP paint gun over the regular kind?
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Old 02-26-2008, 09:30 PM   #2
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Some caveats up front. What I'm going to try to do is describe the basics for shooting automotive paint using an HVLP style gun... I'm not going to stray into the realm of rollers and airless sprayers, I'll let someone else tackle that, I'll try to describe how to put the paint on in the same way GM did it the first time around. I'm also going to assume that the reader will take the proper precautions: Suit up, have a good source of fresh air, and good ventilation...whether you set up a home-made booth in your garage with sheets of plastic or rent some time in somebody elses booth.

Equipment needed:

1. HVLP gun (any manufacturer) A small, gravity fed, touch-up gun is a good starter tool to learn on. I recommend this over a full-size siphon feed gun for a beginner because they aren't ready to try to paint the entire car in one try...so they don't need that much paint in the pot at any one time....nor is their wrists ready to go slinging that heavy gun around for a couple of hours...that takes time.

2. Compressor. Not much is needed, but they are handy. Buy as much compressor as you can afford.

3. Regulator with water trap. Don't skimp on this, get a good one.

Ok, the first thing to do is to learn how the gun patterns. This is done with cardboard and whole milk as a substitute for "paint". When you mix paint and reduce it to the correct viscosity to shoot through the gun, it will be about the same consistancy as the milk, so you'll get the hang of how much air pressure is needed to move it through the gun.

Set the regulator so it is putting out 10 psi with the trigger of the gun pulled back. You should never need more than that (if 10 psi will not flow paint, then clean the gun out and reduce the paint more)

There is often an extra regulator **** on the handle of the gun...you open that till you hear a little hiss of air and the regulator on the compressor doesn't jump up and down every time the gun'* trigger is pulled. It'* an air bleed screw..it allows the pressure to bleed off and will also take accumulated water out of the air line. The end result is that you don't get a "SPLAT" of paint comming out the gun'* tip when the trigger is pulled.

If you look at the gun, there'* only one other adjustment on a single action, that is the position of the needle in relation to the opening in the tip..this is like the mixture screw on a carb..it regulates the maximum amount of paint that can be sucked through the tip for any given pressure...you'll be playing with that adjustment a lot while painting. Moving the needle back will put out more paint, moving it forward towards the tip will thin the mixture out with less paint in the air.

So, with 10psi of line pressure, correctly reduced (thinned) paint in the gun, and the needle set to the correct mixture, the paint will spray an even fan of wet paint. You want a light spray that will stay liquid for the 6 to 12 inches it has to fly from the tip of the gun to the surface of the car you are trying to paint.

If you get the mixture too thin, the paint can start to dry in mid-air...so it hits the surface and creates a sandy, pebble covered film.

The other end of the spectrum is too much paint for a given pressure...the paint goes on too heavy and creates runs and sags in the finish (paint is going on so thick that gravity can distort the surface before it starts to harden.)

That'* how the equipment works...now, how do you use it right?

The first thing to learn is how to apply an even "stroke" of paint from the gun. Just like painting with a brush, painting with a gun requires training your hand to do a repetative motion. You want to move the spray gun in a nice even line across the part, at a constant speed, and about 6 to 12 inches away from the surface of the part.

First, you always turn the spray on before the gun crosses onto the part being painted..You never point the gun at a part being painted and pull the trigger (unless, of course, you really like sanding out runs, sags, and other blemishes in the finished product )

Next, you always wait until the gun leaves the area being painted before releasing the trigger to turn off paint flow...same reason as turning the gun on, turning it off usually causes a little spatter of paint that you don't want on the part (more sanding.)

In the middle is the hard part. Keeping your hand and the gun moving at a constant speed and distance from the part. Practice is the only way to teach this. If you use milk for paint and a piece of cardboard, you can see the fan of "paint" hit the cardboard and wet the surface. The goal is to put down an even stripe of paint with every pass of the gun, and then learn to overlap the stripes, starting at the top of a part and working your way towards the bottom.

Ok...first cup of coffee is gone, time for a refill...





please fast forward to end of tape and change to side "B" to continue...
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Old 02-26-2008, 10:36 PM   #3
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Ok, more coffee and ready to type some more...

First, to answer a question posed at the top of the thread: "Why an HVLP gun?"

High Volume, Low Pressure (HVLP) spray equipment is a result of a mandate by OSHA and the EPA. Conventional spray guns operate at higher pressures and produce more overspray. In the 80'*, California cracked down on the waste/pollution being put out by the car manufacturers. They fixated on the paint spraying technologies being used and forced this new technology into use before it was fully developed.

An example of this would be the F-Bodies produced at the Van Nuys, CA plant had paint jobs that truly sucked (paint sluffed off the metal after only a few months..sometimes even before the cars were sold by the dealers) vs. the exact same cars produced at the Norwood, OH plant. The difference was the reformulated paint and the HVLP spray guns used to apply it.

Fortunately, the technologies have matured. HVLP guns are now the standard type used in painting automobiles, waste less paint in process, and the paint formulas accomodate the application method quite well.

If you are going to start learning how to paint, you might as well learn on an HVLP to start with...pretty soon you will not be able to buy anything else anyways.

Ok, back to painting....

If you practice the basic stroke for a while, you are just about ready to start shooting real paint onto real parts...or at least a piece of scrap plastic sheet or an old fender to start with.

Some tactics need to be employed when painting real three-dimentional parts. First, spraying paint doesn't like to turn the sharp corners at the edges of panels. Pretty obvious eh? So, if you are likely going to create a running blob of paint on your parts, it'* going to happen at the edges of the panels. If you are painting your bedroom, then you "cut in" the corners with a paintbrush before rolling on the paint on the flat surfaces of the walls right? When painting parts, you do the same thing (called "jambing" since it is the process where the door jambs get painted first). You come in at an angle or from behind the edge of the panel and spray a light coat of paint. Then you paint the big flat areas of the panel from the front using the even strokes of the spray gun. By wetting the sharp corners with paint first, the spray from the long strokes will have a wet surface to bond with..litterally pulling on the wet paint and making it turn the corner.

Another tactic is the order in which you apply paint. You ALWAYS work from the lightest colors to the darker colors. Nearly all paint is formulated to have the correct color when applied to a neutral base color...wouldn't you know, that "neutral" base happens to be "Primer Grey" So primer grey is the first paint color to go on the car body..usually as part of the prep work before painting. If you dissassemble the car, you will often see other primer colors...like Zinc Chromate which hase a distinctive light green tint... These special primers are more for corrosion resistance in special applications. The universal color of body primer is grey and that'* what the colored finish paint is intended to cover up properly. There are some special paint colors that need a different base (I got a can of Suzuki "Candy Napolean Blue" that needs a special base color) but in these cases, the instructions will clearly call out what base color the paint has to be applied over in order to produce the correct finished color. If they don't specify t, then it'* assumed to be grey. From that point on, you stick to the "lightest to darkest" with white at one end, black at the other. A dark color will always cover a lighter color without requiring an excessive number of coats to get the job done.

After color, come the question "how much" of the car to paint at once? A pro will do the entire car as one assembly because he wants to get it done with the minimal amount of effort. One the other hand, General Motors DID NOT paint the entire car at one time. Take a close look when prepping the car...you will find that a lot of panels on the car were painted prior to assembly. Yet, the finished car matches in color? Yep, you don't have to paint the entire car in one piece in order to get an even color in the finish. If you use the same batch of paint, mix it the same way, and apply it in the same manner, you can get the entire car comming out with the same color...even if you paint it one piece at a time.

So how much should you paint at once? I try for an entire assembly at a time. A hood, a door, a trunk lid, etc. Parts that are logically a single chunk of the car. It''* a heck of a lot easier to remove a door, strip it of all it'* parts that don't get painted, then paint the entire door, vs. trying to mask off the frigging door on the car and paint just the outer door skin without getting paint on anything else. Painting the part off the car is also a better approach if you are changing the color of the car. Off the car painting allows you to replicate the method used by the factory. If it wasn't for the build sheet codes and body tags, only another pro could figure out the car didn't leave the plant that color...this is also the method prefered by the folks doing restoration work. (they are just even more annaly retentive..trying to achive even the proper "overspray" patterns on the car...as if GM actually DID paint the car that color at the factory.)
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Old 02-26-2008, 11:46 PM   #4
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If you need an extra buffer tank, make sure it has a drain petcock in the bottom. Condensation inside the tank needs to be drained off at regular intervals. The last thing you want is a big splat of water comming out with the spray of paint.

In drying out the air from the compressor, you have defense in depth... the tank will collect some of the moisture, the water trap on the regulator will get some more, and last the bleed valve on the gun will get most anything that gets past the other two

Ok... Solids, Metallics, Clearcoats, Candies, and Pearls.....

They are all different types of paint and produce different effects in the finished paint. I've also ordered them in level of difficulty to apply.

Solids are just that..a single pigment paint (or a mix of different pigments that produce the desired color as if it were a single pigment.) Solids are rarely used as a finished product anymore, though up till the 1960'*, solid colors were used a lot by auto makers as the final color of the car. Solids still exist though...they are often the basic color to which other effects are applied. These are pretty easy to apply. Mix, reduce, and catylize per the manufacturers instructions. Shoot in even layers until the paint is thick enough to appear to the eye as a single color. Since there is nothing else in the paint, these are also the easiest colors to fix "oops" mistakes in. You get a sag or a run? No sweat...let it cure completely and wet sand your mistake away...no harm, no foul. Run up the air pressure too high and create a surface that looks like the peel of an orange?..no harm, let it cure and sand it out....you get the picture, solids are "goof proof" paints. You see one used all the time...the satin Black used on cowls, mirrors, trim metal, etc.

Metallics are solids with a twist...flakes of aluminum, plastic, or some other metal mixed into the paint. Still pretty easy to apply when properly mixed so the metallic components are evenly distributed in the solid pigment that is part of the mix. Application is pretty much the same, but you need to be more carefull...the occassional "oops" is a little harder to correct. Surface defects are more difficult to sand out and still have an even finish, since the flakes tend to float up to the top surface of the paint as it cures. Sand out a run in a metallic paint and you are likely going to see a spot where the run was...it shows up as spot where there aren't as many fleck of metallic stuff..giving the finish an uneven look. To fix it right, sand out the defect to get a level surface, then apply another thin layer of metallic paint to fix the finish. If you get a run near the edge of the pannel, run your mixture all the way down so the gun is blowing nothing but air, and blow the run off the edge of the panel...it usually works and you have nothing to loose in trying..you may just save yourself another coat of paint and some wet sanding time.

Candies...these are "mid" coats of paint in a clear base. They get applied over a solid or metallic base coat. Candies are cool in that with every successive coat, the effect becomes more pronounced... it'* like a "Super" metallic paint. But, it is increasing less forgiving of mistakes in technique. Wanna see a bad candy paint job? Just look for just about any "donk" running on the street... I haven't seen a single one yet with a decent candy paint job...nearly all of them are uneven and over done. Barf.

Pearls... The absolute bitch of paints. As a "Mid" coat paint, Pearls are like candies, only the effect is like ground up mother of pearl in a clear base (hence the name). It'* the trickiest of all the paint effects because it is so easy to over-do the effect and almost impossible to get a match over multiple parts...this is one of the few examples where everything must be painted at the same time. What makes a pearl so hard to apply is the vast difference between what the paint looks like when wet vs. when it drys. You can't see what you are doing when applying it. You mix it up, shoot a single coat, then wait to see what happens as it dries. If you see an even sparkle to the finish base color, then you did it right (pat yourself on the back ) If you blew it..you will see milky splotches on the finish where the pearl coat is too thick. If you really screwed it up then the entire paint job will look like a frosted Christmas tree ornament...break out the buckets and sandpaper, take it all off and try again "you know, having a car with just a plain metallic finish isn't so bad"

Ok, I skipped clear coats... which as the name implies are clear layers applies over top of any of the above finishes to give the paint a perpetual "wet" look. Easy to apply, shoot it just like a solid coat. Fix your mistakes just like a solid finish. Warning: Don't go overboard! It'* hard to see what your are doing when applying clear coats...it looks wet all the time and it'* really easy to put on too thick...and thick paint chips off too easily. If you did your prep work properly to get a smooth surface, and applied your base coats properly to keep the surface smooth, then you don't need many coats of clear to make the car look wet all the time.
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Old 02-27-2008, 12:12 AM   #5
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When painting PANELS, not a whole car, a 15 gallon tank was not enough for me. I added a buffer tank, for a total of 22 gallons. I ran my final regulator on the buffer tank.

It was just enough reserve for me, but I ran my gun at a slightly higher pressure than advertised. For the rookie, a slightly higher pressure (50% over suggested MAX) will help you control your paint a little better. This eats up the air though.

You need to match your compressor to the specs of the HVLP gun, or very close. When doing panels, 75% of the guns needs are OK on the compressor if you run a buffer tank, but if it'* a whole car, you better be 1:1 or better.

Once you have your air supply and demand where you need them, the next most important step is prep between coats. EVERY coat. After that, dust control is probably next, or even before. Wetting down the 'walls' and floor of my redneck paint booth 5-10 minutes before the next coat was sprayed was a HUGE part of my success.
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Old 02-27-2008, 12:36 AM   #6
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Mix..Reduce...Catalyze...

Sorry if I bounced those terms around without explaining them earlier...

Modern automotive paint is an epoxy. It doesn't just "air" dry, it actually lights off and cures like epoxy glue. It is also nearly impervious to solvents once it cures fully, making it perfect for automobile use (spill some gas on it while filling up the tank, no worries 'cause it aint comming off )

When you buy your paint, it will be part of a system of chemicals. To insure they bond properly, I try to use all of the paint layers from the same system..primer, base, mid, and clear.

When you buy the paint, you will pick the colors you want for the finish product and the fellow behind the counter will start mixing cans of base per the formula that goes with the color...then he/she will start handing you other cans of all the other components that must be mixed just before the paint is shot in your spray gun...along with the "cookbook" recipie of what to do. Probably also tell you what you will need to clean the stuff out of your paint sprayer when it comes time to clean up (typically Acetone, but could also be Styrene or a whole host of truley obnoxious chemicals...read the warning labels )

For a typical paint there is a Catalyst chemical that is mixed in a set ratio to the base (the actual "paint") This is the stuff that makes the paint turn into a thin hard waffer of paint when applied.

There is also a Reducer chemical...this takes the paint and makes it thin enough to shoot properly though the spray gun. The ratio of reducer to paint varies with temp and humidity (there are also ranges of reducers to pick from...you can make the paint cure slower, faster, in hot humid weather, etc, etc. just by changing the reducer used. The guy behind the counter will coach you on what will likely work the best for you.

How to you mix paint? You stir the stuff !!!! Do not attempt to simply shake up the can...it will work for the mechanical paint mixers in the store, but doesn't work for the fellow trying to shake up the pint can with bare hands alone. No, follow the recipe and stir up the paint per the instructions. You will also need some plastic measuring cups and some straining filters (get them whle you are there buying paint....most of the time the person behind the counter will just hand you a stack of them gratis...hey, you did just spend several hundred dollars on the paint !!

Ok...now, when it comes time to paint, mix up a little batch during practice time. Don't waste paint by mixing more than you can use at a time...paint has a "pot" life...the time it will stay liquid before it starts to cure in the mixing bowl. As soon as it is mixed, the clock starts running.

When you are done shooting paint... don't just hang up the spray gun and admire your handy work. You need to clean the paint out of the gun. Pour out the excess paint, load the gun full of solvent, and start spraying the solvent into a rag. Once the rag is damp, bring it in contact with the tip of the paint gun...a neat thing will happen...bubbles will start forming in the color cup as the air from the tip gets turned around by the rag and blows the paint & solvent back into the cup. Dump the solvent and repeat this several time. This is back-flushing the spray gun and it will get nearly all of the paint out of the gun'* internal guts. If I am just going to resume painting within 24 hours, I'll back flush the gun with solvent, fill it with clean solvent and hang the gun up...it'* clean enough to leave sit for a day or two. If I'm done for a while, I'll back flush the gun, then take the entire gun apart and wipe all the pieces clean, lube them with petroleum jelly, and reassemble the gun for long term storage.
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Old 02-27-2008, 01:33 AM   #7
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Another word on moisture control: I run two water traps in series. A better way, however, is to find a radiator, large heater core, or similar, put it in a barrel of cold water, and run your air through that. The cold water in the barrel will cause any moisture to condense on the walls of the radiator core before it can get to your gun. I find this excessive, but my uncle won't paint without it. If you use this method, you have to dry the radiator out periodically (at the end of the day), or puddles will accumulate and you'll still get a splat of water. To find out if you need more moisture control, hook up a typical blowgun and just blow air on your hand for a few minutes, long enough for the compressor to have replaced all the air in the tank with newly charged, heated air. If your hand gets damp, you need to take more measures.

Painting Aluminum:

Aluminum is trickier because paint does not like to stick to it. (ever heard of 00+ hood herpes?) When sanding the bare metal, don't use anything finer than 180 grit because the primer needs a rough surface to cling to. Next, you need a special primer that is rated for aluminum. An example is PPG'* DP line. It is a two part epoxy, and it'* pricey, about $90 a gallon. After spraying the primer, wait a couple days for it to etch before painting. (depending on your brand)
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Old 02-29-2008, 09:44 PM   #8
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Quote:
Originally Posted by 2000SilverBullet
In frikken impressive info. Keep it coming.
Well, there comes a point where you can't teach by reading, you have to pick up the tools and give it a try.

I have an advantage...I've been doing this stuff for 30 years. One Christmas, many years ago, I got a Remington 511 rifle and enough gift cash to go down to the hardware store...spent 50cents on a box of 22LR'*..spent the rest on a Badger 100 single action airbrush. I used an old tire as my "air tank"...I got pretty good using both of them I wish I could drive an airbrush like Varga, but oh well...

So, the next step really involves getting your spray gun and starting to practice using it. Getting familliar with it'* controls and trying to spray some patterns with it.

There are some neat tricks you can do with the pattern..like fading colors together by angling the basic stroke (you're playing games with the density of the fan pattern comming off the tip of the sprayer,..making it dense on one edge, diffuse on the other.)

Next you can start playing with stencils and masking colors in reverse...Following the rules of always working from light to dark colors, you lay out the graphics so the light colors get painted, masked off, then move on to the next color, etc....when you get to the darkest color, start peeling off the masking to reveal the finished design.

Another trick is using a incompatible paint as a masking agent (instead of tape)...for example..cheap water based paints don't stick to rubber or glass very well...and epoxy paint will not stick to water based paint...so you can use a water based paint to mask off areas that would be hard to mask with paper and tape.
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Old 05-18-2009, 11:49 AM   #9
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Those guides are all well and good, but here'* how I'm planning to go about it.

1) Save up some dough.
2) Be friends with a guy who works at a shop that does painting.
3) Pick a color.
4) Pay discount price.

LOL.
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Old 02-26-2011, 12:02 PM   #10
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I'm sure guys like that can smell gold diggers like you a mile away :
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