I'm painting a gas tank on my HD. I tried to sand out a small piece of trash and sanded through the color and down into the primer. When I continued applying the black it busted in a circle around the area where I sanded through to the primer. What happened?
The solvents in the color crept past the edges of the first coating and lifted it. The solution is to sand out the wrinkles and cover the area with sealer. That will stop the lifting.
I'm having a problem blending the black on my street rod. Got any tips?
Yep, I do. First, blending black is next to impossible if you are working with a single stage urethane. Doing so will almost always leave a color ring around the repair. With a lot of practice you can blend clear over a black base coat but even that is difficult. I suggest forgetting about blending and think about where you can use a line break or just spray the entire panel.
I've heard of 'die back' after painting. I have sand scratches showing in my finish. Is that the same and if so how do I stop it?
That's what 'die back' is, sand scratches showing in the finish. The fix is to repaint. The prevention is to not apply so many coats of primer at a time. I usually apply 3 coats, sand those then appy 2 more. Urethane primers were supposed to put an end to 'die back' but it still happens, especially when using cheap primers.
I'm having a real problem with yellow paint. It is taking six coats to get good coverage. Is this normal?
Yes, it is normal for yellow colors to be very transparent. What I do is apply a coat of white base before spraying yellow. Good coverage can still take three coats, but that's better than six.
Is it really necessary to apply epoxy under the bondo? In the old days we applied bondo directly to the metal and it worked okay.
I did the same thing for years, applying bondo to metal. But I like the idea of being able to sandwich the bondo between layers of epoxy to stop moisture from reaching the bondo.
What about using an air brush for touch up?
You can provided the color you are touching up is a solid, no metallic. The air brush tends to leave metallic finishes lighter than they should be. To touch up metallic finishes use either a touch up brush or a mini spray gun.
So when are you going to produce a new paint and body DVD?
I"m working on a new set right now. Should be ready by the end of the year.....hopefully.
The cheaper the clear coat product the shorter the life span of the finish. That's just the facts people
Your DVD's are fantastic! How about doing a short DVD on primers? I know lots of people get confused about which primer to use where.
Thanks. Glad the DVD's are a help. That's why we did them. It cost a ton of money to produce DVD's, but I think you may be on to something. Primers can be confusing, and they aren't cheap. Let me see what I can do.
Is it true that clear coats can yellow? You bet it is. That is why I stress purchasing quality products. Cheap clears will not only yellow over time they will also peel off.
How long should you allow urethane primer to cure before sanding? The P Sheets say 24 - 48 hours. A friend in the street rod business tells me he gives the primer at least a week to cure. I've started the same thing in the shop so we'll see if there is any difference.
Don't forget to change the inline filter attached to the inlet of your spray gun before painting. This is the last line of defense against moisture entering your gun.
Try the new 3m "blue" masking tape on areas prone to being scratched as you assemble your ride. The blue tape will easily peel off after a couple of weeks.
Finish your plastic body repair work in 180 grit before priming. Once primed allow the primer to cure for at least a week to reduce the chances of the primer shrinking after it is sanded.
Your new can of epoxy primer states there is an induction period before the product can be used? If so you must allow the mixed primer to sit on the bench for the stated induction time or the primer may never dry once applied. To avoic this problem always purchase epoxy primer hardeners that do not require an induction period.
Toss the old style syphon type spray gun and try a new gravity feed gun. You will never go back to the old ways!
To reduce the time spent compounding try finish sanding with 3M 3000 sand paper. You will be surprised at how much time this saves in the compounding department.
Can fish eye be removed?
Try sanding the individual fish eye spots using a Scotch-brite pad to be sure you sand down in the fish eye, clean the area with degreaser then fill the spot with clear. Once cured, sand the clear drop smooth and compound.
What is a solvent pop?
You need to check out my newest DVD - Curing Paint Problems. I discuss this problem and how to prevent it.
But to answer your question a solvent pop is just that, solvent from the initial coats of clear moving up through the final coats and erupting on the surface.
I"ve got bubbles coming up on my fresh paint job. Why?
Most often this is due to the painter having waxed the surface before the finish has had a chance to cure. Wax can trap solvents and the result is bubbles in the paint. The fix is to remove the bubble and paint again. The prevention is to not use wax.
How do I get a good color match?
These days it is a matter of calling your local paint rep and asking him to do a computerized color match.
The computer will determine the best match, most of the time dead on, and all you have to do is figure out how to
spray it on. I cover this problem in our new DVD.
The sealer wants to wrinkle when repairing a small paint chip.
Try applying the sealer in mist coats, waiting at least 20 minutes between coats. This method may take as many as 5 coats to get coverage, but it should stop the sealer from trying to wrinkle.
Why does the sealer wrinkle? Usually this is due to repairing a VERY fresh paint job.
Professional painters make the task of refinishing a vehicle look easy. Yet despite having years of experience plus a certain degree of talent the real art of painting begins with having the right tools, and more so, knowing how those tools are used.
Of course the most prominently displayed tool the painter uses is his spray gun, and admittedly, most of us associate a fine refinishing job with what comes out of that gun. Reality is a lot different. If you ask a painter how he painted a particular vehicle he will most likely tell you he simply put on enough coats to make it shine and stopped. What he didn’t tell you was which spray gun he used, how he applied each coat, how much overlap he used when he applied those coats, why he kept checking his watch as he painted, and last of all, what he did for the 24 hours immediately after the vehicle was sprayed.
The spray gun.
I could spend a lot of time just going through the basic spraying differences between the old line conventional siphon feed spray guns versus the newer HVLP gravity feed spray guns using whatever type of paint we chose to discuss. But I’ve decided not to do that. Instead, I’m going to concentrate solely on spraying techniques using HVLP gravity feed spray guns simply because the old line conventional siphon feed spray guns are on the way out. At this moment the use of these guns is illegal in some states (for professional use) and I suspect that trend will continue with the Binks #7, for example, someday becoming a museum piece.
Handling the gun.
The first thing every good painter does after he loads his gun is to spray a test panel. That panel may be a 3 X 5-inch color match panel or it may be half the wall behind the spray booth. The point is, before he steps into the spray booth he needs to know exactly how his gun is going to spray whatever material is in the gun.
A lot of this becomes automatic over time. Whether you spray acrylic enamel all day, everyday, or base coat/clear coat all day everyday you quickly develop a feel for the proper spraying techniques needed for a particular finish. Which is just the point. You have to know what the correct techniques are before you can develop them.
Establishing the right spray pattern.
No matter what type of paint you are spraying, whether lacquer, acrylic enamel or the newer (and more preferable) urethane based finishes, the correct spray pattern is an oval pattern about 2 inches wide by 6 inches in height.
Begin by adjusting your spray gun for maximum performance. All HVLP spray guns have two adjustment knobs located at the upper rear of the handle. With no air connected to the gun, unscrew the lower knob, or air flow adjustment knob, about five revolutions (or just before it releases and comes off the gun). Depress the spray trigger fully. Now screw the knob clockwise until you feel the spray trigger begin to move. Stop, the airflow adjustment is set.
The upper knob controls the fluid output. Begin by turning this knob clockwise until it is just snug against the gun housing. Connect the air supply and while holding the gun at 90 degrees to and six to eight inches from a test panel spray a two-second burst onto the test panel. The result should be a very wet, very round spray pattern. Turn the knob counterclockwise 1/8 turn and spray another test pattern. The pattern should begin opening into an oval shape. Continue opening the knob in 1/8 turn increments, checking each setting by spraying a test pattern, until the pattern widens into a six inch long fan while the gun is held at 90 degrees to and six to eight inches from the test pattern.
Six to eight inches from the surface should optimize the atomization of the material being sprayed. Positioning the gun beyond the eight inch mark can result in a diminished amount of atomized material hitting the surface as a fine mist and an increased amount of the atomized material reverting back to droplets as they hit the surface. Droplets will appear as an uneven texture on the surface.
All that is left now is to spray a couple of test passes to be sure the gun is set correctly. Coverage.
Once you have the gun spraying the correct pattern your next feat is to establish the right amount of coverage. Load the gun, pull the trigger and start moving. You are now getting coverage.
The question is what kind of coverage are you getting? Perhaps to better
explain what coverage actually is, is to say coverage is the amount of paint being applied to a surface using either light, medium wet or wet coats.
A light coat, or tack coat as it is more commonly referred to, when sprayed on a one foot long by six inch wide test panel will require one second to make the spray pass. The result will be a very thin, somewhat transparent and rough coat of paint.
To cover the same size panel with a medium wet coat will require a two second spray pass, and to apply a wet coat will require a four second spray pass. A medium wet coat will cover the test area completely with a smooth even coat of paint. A wet coat will also cover the test area completely with a smooth even coat of paint but will begin to run after a few more seconds have passed.
Next is overlap.
I’m going to talk about overlap in terms of percentages, such as 50% and 75%. The best explanation I can offer goes as follows: Starting at the top of the panel you are spraying, make your first pass half on the masking paper and half on the panel. Moving down three inches from the top of the first pass, your next pass will begin at the very top of the panel. The top three inches of your spray pattern will overlap the bottom three inches of the first pass and the bottom three inches of the second pass will cover the next three inches of the panel. Continue this method until the panel is completely covered. This is a 50% overlap
A 75% overlap would start the second pass at one and one half inches down from the top of the first pass (still on the masking paper) continuing downward in the same back and forth manner until the panel is completely covered.
Always hold your gun 90 degrees vertical to the panel you are spraying. The only exception to this rule is when spraying a flat panel such as a roof, hood or deck lid. To maintain coverage on these panels try holding the gun vertical, but tipped forwards about 30 degrees from vertical and use a 75% overlap. Spray all flat panels beginning at the edge nearest you and working your way across the panel using the 75% overlap spray pattern.
The clock.
With the exception of base colors, all of the finishes we use today employ a hardener, which means you have a specific time frame to work within once a coat of these products has been applied to a vehicle. Applying a second coat too early will not only increase the chances of getting a run, it can also trap solvents and cause solvent pops (check out our new dvd Curing Paint Problems for more info) in your finish that will require sanding to remove. Waiting too long before over coating can result in poor adhesion and the possible failure of the over all finish.
If that isn’t enough to get you to keep an eye on the clock, just let a cup of clear coat (or any other product) catalyze in your spray gun. Cleaning the gun after a product has set up is like trying to clean the inside of a soda bottle with a cotton swab, only harder.
Every catalyzed product also has a minimum amount of time you should wait before sanding or polishing the final finish. This delay gives the finish time to dry and cure out before doing any additional work to it. The norm here is 24 hours.
Everything I’ve said up until now falls under the category of preparation. Because if you haven’t done, or made provisions to do, everything absolutely correct up until this point, no amount of talent, art or just plain luck is going to help you achieve the results you want.
Now for the art.
My mother, a renowned artist, once told me putting paint on a canvas was
easy. The hard part was in knowing which brush to pick up and how to lay down each stroke. Refinishing restoration projects requires the same kind of knowledge.
Primer.
Spray all primers using the gravity feed HVLP with a 50% overlap and medium wet coats. Allow 10 to 15 minutes between coats and at least 2 hours cure time, but not more than 12 hours, before sanding. Pot life at 68 degrees F. is approximately 1 hour. (Pot life is the amount of time a product can remain in a gun before beginning to set up.)
Sealer.
Spray all sealers using the gravity feed HVLP with a 50% overlap and medium wet coats. Apply only one coat and allow 10 to 15 minutes cure time before applying the base color. Pot life at 68 degrees F. is approximately 3 hours.
Base Coat. Using the gravity feed HVLP apply each coat with a 50% overlap and spray medium wet coats.
Base coats dry to a flat finish, which can be scary at first. You can’t tell what the final outcome of your refinishing job will be until you apply the clear coat over it. Warning! Applying the clear coat is like pouring concrete over your sprinkler system. Anything under it is there forever, unless you want to try and remove the concrete. Take care of any imperfections in the base coat before applying the clear coat. Tip. After sanding out an imperfection in a metallic base coat the repaired area can be recoated to blend into the surrounding paint without adjusting the mixture of the base coat. The old method of blending required adding additional reducers or thinners to the paint mix in order to get the paint to flow into the surrounding area and not leave a rough edge. Properly mixed base coats will blend without leaving any trace of a rough edge. (again, in our new dvd – Curing Paint Problems)
Allow 10 to 15 minutes between each coat of base color and 15 minutes before covering with a clear coat. Base colors may be masked (for two tones) after 30 minutes at 68 degrees. No pot life. Must be clear coated within 12 hours to insure good adhesion.
Pearl Base Coats.
If you have ever sprayed a “true pearl” through a conventional spray gun you know what a nightmare the application of this finish can be. If it doesn’t mottle or blotch you probably haven’t sprayed it on wet enough. If it does mottle and blotch you have probably sprayed it on too wet.
The newer pearl base coats that come on late model vehicles are a dream to spray. They don’t mottle and they don’t blotch. Of course there are a few tricks to spraying the new pearls.
Spray medium wet coats. Instead of the 50% overlap used on most base coats you will need to step up to a 75% overlap. Something else I like to do is apply an under-base color, even if I have tinted my seal coat. For example, if the pearl I am spraying is red I will apply a red under-base coat over the sealer. As pearls are extremely transparent this gives me good coverage with a minimum of coats, and besides that, the overall finish just looks better.
Allow 10 to 15 minutes between coats and at least 15 minutes before adding the clear coat. No pot life. Must be clear coated within 12 hours to insure good adhesion.
Candy Base Coat finishes are almost as easy to spray with a HVLP as Pearl Base Coats. Use 75% overlapped medium wet coats with a 2 inch wide by 6-inch long pattern. Put on 4 coats of base color followed by 4 coats of clear. A trick you can use is to tint the silver (the most popular color) under-base coat towards the same color you are applying the Candy color in. For example, if you are doing a Candy red, try tinting the silver under-base coat slightly red. You will still need to apply the 4 coats of base color over the tinted silver, but the depth appearance of the finish will increase dramatically.
Allow 10 to 15 minutes between coats and at least 15 minutes cure time before applying the clear coat. No pot life. Must be clear coated within 12 hours.
Urethane Clear Coat. . Apply urethane clear coat finishes using 50% overlapped medium wet coats with a 2 inch wide by 6-inch long spray pattern. If you have ever sprayed acrylic enamel you are in luck. Urethane clear goes on almost identical to acrylic enamel. Both are finicky, (will run easily) but surprisingly user friendly when applied with a HVLP spray gun. The primary difference in spraying a urethane clear coat and applying an acrylic enamel finish is that the clear coat is a high solids material. Which means the urethane clear does not flow out like acrylic enamel and even tends to orange peel when applied. That’s a warning to prevent you from trying to flow out a clear coat by applying it wetter or over reducing it. Urethane clear coats look their best when sanded smooth then polished to bring out their shine.
Allow 5 to 10 minutes between coats. Pot life is approximately 1 hour at 68 degrees F. Can be sanded and coated again to remove imperfections after 12 hours. Allow at least 24 hours before polishing. (great info on spraying clear coats in our new dvd Curing Paint Problems)
Spraying acrylic enamels with the HVLP.
Use 50% overlap and medium wet coats. Note: The metallic flakes in acrylic enamel are larger than those used in base coat/clear coat finishes. Most HVLP spray guns come equipped with 1.4mm spray nozzles. To effectively spray metallic acrylic enamels the spray nozzle must be replaced with a 1.7mm or larger spray nozzle.
Acrylic enamel has to be one of the most difficult finishes there is to spray. In the business, we say this finish tends to “flow”. Which means just when you think you have laid down the perfect coat, it sags and begins to run. To help prevent runs spray on a light tack coat then immediately follow that coat with a medium wet coat. The tack coat helps the medium wet coat adhere better and reduces the chance of runs.
Because acrylic enamels tend to “flow”, even long after you have sprayed on a coat, you must give each coat sufficient time to dry before applying the next. Use the finger test to check for tacky condition before applying the next coat. Since you began your first coat half on the masking paper, touch the painted masking paper with your latex-gloved finger. If the paint strings out as you remove your finger the paint is too wet and needs more time to dry before applying the next coat. If the paint is tacky but doesn’t string away as you remove your finger the coat is dry enough to be coated over. This is a simple test that will almost eliminate any chance of runs.
Although spraying with a HVLP will reduce this possibility, metallic acrylic enamels are famous for their tendency to mottle, or become blotchy as you apply subsequent coats. One technique you can use to prevent mottling is to apply each of the medium wet coats using horizontal strokes while immediately following each of these coats with a vertical stroke light coat. Be sure to adjust the air cap on your gun by 90 degrees in order to maintain the correct gun positioning.
An application method we used in the olden days was to divide the vehicle into five sections; right side, left side, roof, hood and deck. We applied each color coat horizontally, one section at a time, then immediately following that coat with a light vertical coat to orientate the metallics before moving on to the next section.
Use the touch test to determine time between coats. Pot life is approximately 1 hour at 68 degrees F. for catalyzed enamel.
Single stage urethane finishes.
This finish is ideal for spraying non-metallic, or solid colors. Single Stage sprays exactly like urethane clear coats and acrylic enamels. Spray with a 50% overlap, medium wet coats using a 2-inch wide by 6-inch long spray pattern. While Singe Stage finishes are considered high solids finishes, you will not experience the same orange peel effect common to clear coats. These finishes can be sanded and polished just like clear coats to achieve that lacquer look we all prefer.
Allow 10 to 15 minutes between coats and at least 24 hours cure time before polishing. Pot life is 1 hour at 68 degrees F.
Selecting the point on the vehicle you want to begin spraying.
Back when we sprayed a lot of acrylic enamel I picked up the habit of
starting at the right rear of the vehicle and working my way around the vehicle by moving towards the right front. I can’t say this is better or worse than any other starting point, it is simply how I know where I began and where I ended each coat.
Spray the entire side of a vehicle at once. Never panel paint unless your intent is to spray only the one panel. Make your first pass at the upper most portion of the vehicle moving from one end of the vehicle all the way to the other end of the vehicle with each pass. Make your next pass just below the first, using the correct percentage of overlap, then follow this pattern until the entire side of the vehicle is coated. Then move on to the next area, usually the hood or the deck lid. By the way, always spray the roof first, beginning on one side (your preference) and working your way across the panel all the way to the other side. Never begin spraying in the middle of a roof, as you will risk ending up with one of those sand papery dry lines right where you began.
Each time you fill the cup pause and clean the air cap to make sure the tiny spray ports remain open. The quality of the spray pattern depends upon these ports staying clear of paint.
After each coat pour any remaining paint back into the mixing cup. Be sure to pour a little lacquer thinner or reducer into the gun to prevent the cup from drying out. When you are ready to spray the next coat pour out the thinner or reducer, stir the paint in the mixing cup, and then return it to the gun via a strainer. Of course, be careful not to contaminate uncatalyzed material with catalyzed material.
Never mix product brands. Think of this as mixing Coke and Dr. Pepper. The result may fill the glass, but it isn’t something you’d want to drink. Sticking to one product brand also goes a long way in the cost department.
The last point about handling a HVLP spray gun you must remember is this: As the cup vent must remain open at all times during spraying, tilting the gun off the 90 degree position to the target can cause paint to seep through the vent and drip onto your fresh paint job. In the olden days we tied a shop towel around the siphon feed cup in a bandanna fashion to prevent drips from the cup vent from getting onto our paint jobs. I suppose this method will work jut as well on gravity feed gun, but I’d rather concentrate on getting my gun handling techniques down right rather than relying on a shop towel to cover my sloppiness.
