spaying paint
1 - 11 of 11 Posts
This is some things I jave saved from MartinSr:
Atomization and gun set up.
By Brian Martin
Being HVLP and low VOC products are the way the industry’s going I will be referring to them in this discussion on painting and paint guns. Most all basic issues dealing with HVLP can be applied to conventional guns, atomization is atomization. The HVLP just arrives at it differently.
The object of the spray gun is to break up the primer/sealer/paint/clear (I will call this “PSPC” from here out) into small particles and lay them in neat little rows on the panel being PSPRed. So the whole outcome rests on how well the gun is doing this. Picture the droplets of PSPC coming out of the fluid tip of the gun and then the air “slapping” them into smaller droplets.
You have two things that help you with this process, air and solvent. Solvent can mean something that is already in the PSPR from the manufacture or something the manufacture has told you to add to it. By the way, you should always mix in proper ratios as instructed in the tech sheet. The thinner (less viscosity) you get the PSPR or the more air you have at the fluid tip of the gun the more it will break up the PSPR. The target for you is getting the perfect balance needed. Too much solvent and the PSPR will have no body, fill, durability, etc. Too much air and you blow the PSPR everywhere but the car, poor adhesion, excessive texture, etc.
So, the answer is proper air supply and gun (and fluid tip) choice and how you adjust it.
With today’s high solids-low VOC (Volatile Organic Compound, you know the bad stuff that goes up into the air we breathe) products there is less solvent. And with HVLP guns there is less air at the cap to break up the PSPC, proper air supply and gun setup is more important than ever.
FIRST THINGS FIRST, your compressor and air supply.
An HVLP gun requires more VOLUME of air to operate (the V in HVLP, High Volume Low Pressure). Now you may notice that your HVLP gun is adjusted at maybe the same PSI as an old conventional gun, around 50 lbs at the gun (many HVLP guns are set at much lower though) so where is the “Low” in PSI they are talking about? It is at the actual air cap where the air and paint come out. An HVLP gun has only 10 lbs at the cap while a conventional has upwards of 50! So the VOLUME of air (CFM, Cubic Feet per Minute) is the key to proper atomization with an HVLP.
This 10 lbs I am mentioning is AT THE CAP where the air and paint comes out. It is not measurable without a special air cap that has a gauge built in to it. This air cap costs about $150.00 (and you would need a different one for every brand and model of gun you use) and is not needed to set up or tune your gun. Just looking at the droplet patterns will tell you everything you need. I only refer to it to make a point about HVLP operation.
If you have a gun that requires 15 CFM you will need a compressor and plumbing that will produce that at a very minimum. There are HVLP guns that need as little as 7.5 CFM so you can get good results even from a smaller compressor. Air supply is a complete subject by it’s self so lets assume that you have the air supply needed and move on to gun set up.
So atomization is the key, but why? Why can’t you just lay it out wet and let it “flow”, as an old painter will say. Picture a jar full of bb’s, they will represent well small, atomized droplets of PSPC. The gaps in between the bb’s is solvent. Now picture a jar filled with marbles, they will represent large, poorly atomized droplets of PSPC. The gaps in between are, you guessed it, solvent.
If you apply your PSPC in large poorly atomized droplets, what you will have is a film full of solvent. This can and will cause slow curing, shrinkage and dieback (the loss of gloss in the hours and days after application).
So, now that we have learned the need for gun set up, how do we do it? Lets start with the fluid tip choice. The newer high solids low VOC PSPC products need to be broken up more, so a smaller fluid tip is needed.
Basically you want the smallest fluid tip that will still allow you to PSPC the particular part you are PSPCing keeping the entire thing wet and in a fair amount of time. In other words a 1.0 tip would be beautiful for clearing one fender, but would be lousy to paint a complete. The application would be way to slow and the first panel would be way to flashed by the time you got around back to it. So you need to compromise, a 1.3 is a great all around tip, while a 1.5 though getting a little big, can get you by. If you read the tech sheet on the particular product you are shooting, it will have a recommendation for fluid tip size.
There are needs for other tips, for instance when shooting polyester primer you may need as big as a 2.3, but for urethanes and epoxies, the 1.3 or 1.4 will work great. If you plan on using a pressure pot or paint a bus, all bets are off and we would need to study a little bit more.
As an example of the use of a 1.3 tip I did a test once that proved the point well. I shot two panels of metal with a med solids urethane primer. One was shot with a 1.3 super high atomizing top of the line topcoat gun. The other was shot with a 1.5 (or a 1.7 I can’t remember) “hoser” primer gun. Three coats were applied and after a full cure (the one shot with the larger gun took MUCH longer to flash and cure by the way) the film thickness was measured. The one shot with the 1.3 tip was 2 tenths of a MIL thicker! The larger gun laid out the marble sized droplets full of solvent and when the solvent flashed the film shrank.
Air supply is a subject that could fill many pages by it’s self. So we are going to assume you have that covered and move on to gun set up.
You need to “tune” your gun EVERY TIME you use it just as you would tune a guitar before you perform. This is done with a very basic spray out pattern test. This very basic test tells you how your gun is atomizing and you adjust it to achieve the best atomization you can.
Lets do a spray pattern test:
Set the fan width as need (you don’t want to change it after you have “tuned” the gun). Turn out the material knob about 2 ½ turns. This is the “mixture” adjustment, kind of like the idle screw on a carburetor. The farther in it is screwed the lower the fluid to air ratio is and the smaller the droplets will be. The farther out it is, the higher the fluid to air ratio is and the larger the droplets.
Set the air pressure at the inlet to the gun to the manufactures specs. On an HVLP gun this spec is usually found on the gun and is the maximum PSI it can have while still maintaining the maximum 10 lb at the cap for legal HVLP transfer efficiency (68 %). You are now ready to do a test spray out.
Tape a piece of masking paper on the wall for the test. Hold the gun at a right angle to the wall, just as if you were going the wall. Hold the gun at a spread out hands distance (about 8” or 22cm). Pull the trigger to completely open for a split second and then close it. You want an ON-OFF wide open-completely closed in ONE movement. You should have a cigar shaped pattern with complete coverage in the center with fading coverage going away from the full coverage cigar shape in the center. The center should be fully covered without any runs. If you have runs, either you are holding the trigger too long, you are too close or the gun is simply applying too much material. In which case you need to screw in the material knob or turn the air pressure down. But most likely if you have turned the material knob out the 2 ½ turns and the air is set at the factory specs, you are just too close or holding the trigger open too long.
The droplets you see trailing off the center are what you will use to “tune” your gun.
Turn in the material knob to make the droplets smaller (and or raise the air pressure). The balance you need to attain is the smallest droplet size possible before you loose the coverage desired. In other words if you turn in the material knob too far, not enough material will be coming out to cover the panel!
Now, you’ll notice that I said, “raise the pressure to the gun”, while earlier I said to set it to manufactures specs. We are talking a very small adjustment. It is a fine balance in material to air ratio and a little more air than specified is okay. Even if it is an HVLP gun the inlet pressure recommended is to maintain the 10 lb limit at the cap. Well, about three quarters of the country has no regulations for HVLP use so if you go over the 10 lbs all it will do is atomize the material a little better. You may loose a little of the benefits of HVLP though. But remember you have a lot of control with the material adjustment knob.
After you are happy with the droplet size, DON’T TOUCH THE FAN CONTROL. It will change the PSI at the cap and will change the atomization you worked hard to get.
Do this spray out every time you spray as material change, temp, and humidity will necessitate a spray out droplet pattern test. Good luck!
http://members.aol.com/icantunderstand/hvlpdropletpatterns.jpg
More to come......
Atomization and gun set up.
By Brian Martin
Being HVLP and low VOC products are the way the industry’s going I will be referring to them in this discussion on painting and paint guns. Most all basic issues dealing with HVLP can be applied to conventional guns, atomization is atomization. The HVLP just arrives at it differently.
The object of the spray gun is to break up the primer/sealer/paint/clear (I will call this “PSPC” from here out) into small particles and lay them in neat little rows on the panel being PSPRed. So the whole outcome rests on how well the gun is doing this. Picture the droplets of PSPC coming out of the fluid tip of the gun and then the air “slapping” them into smaller droplets.
You have two things that help you with this process, air and solvent. Solvent can mean something that is already in the PSPR from the manufacture or something the manufacture has told you to add to it. By the way, you should always mix in proper ratios as instructed in the tech sheet. The thinner (less viscosity) you get the PSPR or the more air you have at the fluid tip of the gun the more it will break up the PSPR. The target for you is getting the perfect balance needed. Too much solvent and the PSPR will have no body, fill, durability, etc. Too much air and you blow the PSPR everywhere but the car, poor adhesion, excessive texture, etc.
So, the answer is proper air supply and gun (and fluid tip) choice and how you adjust it.
With today’s high solids-low VOC (Volatile Organic Compound, you know the bad stuff that goes up into the air we breathe) products there is less solvent. And with HVLP guns there is less air at the cap to break up the PSPC, proper air supply and gun setup is more important than ever.
FIRST THINGS FIRST, your compressor and air supply.
An HVLP gun requires more VOLUME of air to operate (the V in HVLP, High Volume Low Pressure). Now you may notice that your HVLP gun is adjusted at maybe the same PSI as an old conventional gun, around 50 lbs at the gun (many HVLP guns are set at much lower though) so where is the “Low” in PSI they are talking about? It is at the actual air cap where the air and paint come out. An HVLP gun has only 10 lbs at the cap while a conventional has upwards of 50! So the VOLUME of air (CFM, Cubic Feet per Minute) is the key to proper atomization with an HVLP.
This 10 lbs I am mentioning is AT THE CAP where the air and paint comes out. It is not measurable without a special air cap that has a gauge built in to it. This air cap costs about $150.00 (and you would need a different one for every brand and model of gun you use) and is not needed to set up or tune your gun. Just looking at the droplet patterns will tell you everything you need. I only refer to it to make a point about HVLP operation.
If you have a gun that requires 15 CFM you will need a compressor and plumbing that will produce that at a very minimum. There are HVLP guns that need as little as 7.5 CFM so you can get good results even from a smaller compressor. Air supply is a complete subject by it’s self so lets assume that you have the air supply needed and move on to gun set up.
So atomization is the key, but why? Why can’t you just lay it out wet and let it “flow”, as an old painter will say. Picture a jar full of bb’s, they will represent well small, atomized droplets of PSPC. The gaps in between the bb’s is solvent. Now picture a jar filled with marbles, they will represent large, poorly atomized droplets of PSPC. The gaps in between are, you guessed it, solvent.
If you apply your PSPC in large poorly atomized droplets, what you will have is a film full of solvent. This can and will cause slow curing, shrinkage and dieback (the loss of gloss in the hours and days after application).
So, now that we have learned the need for gun set up, how do we do it? Lets start with the fluid tip choice. The newer high solids low VOC PSPC products need to be broken up more, so a smaller fluid tip is needed.
Basically you want the smallest fluid tip that will still allow you to PSPC the particular part you are PSPCing keeping the entire thing wet and in a fair amount of time. In other words a 1.0 tip would be beautiful for clearing one fender, but would be lousy to paint a complete. The application would be way to slow and the first panel would be way to flashed by the time you got around back to it. So you need to compromise, a 1.3 is a great all around tip, while a 1.5 though getting a little big, can get you by. If you read the tech sheet on the particular product you are shooting, it will have a recommendation for fluid tip size.
There are needs for other tips, for instance when shooting polyester primer you may need as big as a 2.3, but for urethanes and epoxies, the 1.3 or 1.4 will work great. If you plan on using a pressure pot or paint a bus, all bets are off and we would need to study a little bit more.
As an example of the use of a 1.3 tip I did a test once that proved the point well. I shot two panels of metal with a med solids urethane primer. One was shot with a 1.3 super high atomizing top of the line topcoat gun. The other was shot with a 1.5 (or a 1.7 I can’t remember) “hoser” primer gun. Three coats were applied and after a full cure (the one shot with the larger gun took MUCH longer to flash and cure by the way) the film thickness was measured. The one shot with the 1.3 tip was 2 tenths of a MIL thicker! The larger gun laid out the marble sized droplets full of solvent and when the solvent flashed the film shrank.
Air supply is a subject that could fill many pages by it’s self. So we are going to assume you have that covered and move on to gun set up.
You need to “tune” your gun EVERY TIME you use it just as you would tune a guitar before you perform. This is done with a very basic spray out pattern test. This very basic test tells you how your gun is atomizing and you adjust it to achieve the best atomization you can.
Lets do a spray pattern test:
Set the fan width as need (you don’t want to change it after you have “tuned” the gun). Turn out the material knob about 2 ½ turns. This is the “mixture” adjustment, kind of like the idle screw on a carburetor. The farther in it is screwed the lower the fluid to air ratio is and the smaller the droplets will be. The farther out it is, the higher the fluid to air ratio is and the larger the droplets.
Set the air pressure at the inlet to the gun to the manufactures specs. On an HVLP gun this spec is usually found on the gun and is the maximum PSI it can have while still maintaining the maximum 10 lb at the cap for legal HVLP transfer efficiency (68 %). You are now ready to do a test spray out.
Tape a piece of masking paper on the wall for the test. Hold the gun at a right angle to the wall, just as if you were going the wall. Hold the gun at a spread out hands distance (about 8” or 22cm). Pull the trigger to completely open for a split second and then close it. You want an ON-OFF wide open-completely closed in ONE movement. You should have a cigar shaped pattern with complete coverage in the center with fading coverage going away from the full coverage cigar shape in the center. The center should be fully covered without any runs. If you have runs, either you are holding the trigger too long, you are too close or the gun is simply applying too much material. In which case you need to screw in the material knob or turn the air pressure down. But most likely if you have turned the material knob out the 2 ½ turns and the air is set at the factory specs, you are just too close or holding the trigger open too long.
The droplets you see trailing off the center are what you will use to “tune” your gun.
Turn in the material knob to make the droplets smaller (and or raise the air pressure). The balance you need to attain is the smallest droplet size possible before you loose the coverage desired. In other words if you turn in the material knob too far, not enough material will be coming out to cover the panel!
Now, you’ll notice that I said, “raise the pressure to the gun”, while earlier I said to set it to manufactures specs. We are talking a very small adjustment. It is a fine balance in material to air ratio and a little more air than specified is okay. Even if it is an HVLP gun the inlet pressure recommended is to maintain the 10 lb limit at the cap. Well, about three quarters of the country has no regulations for HVLP use so if you go over the 10 lbs all it will do is atomize the material a little better. You may loose a little of the benefits of HVLP though. But remember you have a lot of control with the material adjustment knob.
After you are happy with the droplet size, DON’T TOUCH THE FAN CONTROL. It will change the PSI at the cap and will change the atomization you worked hard to get.
Do this spray out every time you spray as material change, temp, and humidity will necessitate a spray out droplet pattern test. Good luck!
http://members.aol.com/icantunderstand/hvlpdropletpatterns.jpg
More to come......
Surface cleaners aka "Wax and grease removers"
By Brian Martin
They are commonly called “Wax and Grease Removers” but many manufactures have changed the name to “Surface Cleaners” or similar names. I think the biggest reason is because the name “Wax and grease remover” implies that they will actually clean all of the wax and grease off the surface. The other reason for a name change is the simple point that wax and grease are only a few of the contaminants that you battle against while painting.
The basic idea behind these cleaners is simple, they are designed to lift the contaminant up off the surface long enough for you to wipe it away. The surface MUST stay wet and HOLD those contaminants up in the cleaner for you to wipe off with a clean/dry rag. That is mistake most make, they let it dry and the contaminant ends up laying right back on the surface. First of all let’s clear up a few things; Lacquer thinner, acetone, MEK, and enamel or urethane reducers are NOT surface cleaners. Lacquer thinner evaporates too fast and doesn’t give you time to wipe it off wet. It is also much to strong a solvent for most cleaning and can get under the edges of sand thrus or soften substrates. Enamel and urethane reducers often have resins and other components in them that are designed to be added to the product they were INTENDED to be used with. To put it in a nutshell, buy and use the products recommended by the manufacture of the paint SYSTEM you are using. A gallon of the proper surface cleaner runs about twenty or twenty five dollars it is money well spent. The gallon will last you through many projects, a few cars even. The pint of paint or clear to do one small redo will cost more than that.
I checked on our paint dept. at work to see how much surface cleaner they go through. We do between 100 and 150 cars a month and purchase three to five gallons of surface cleaner. We purchase about $12,000 a month in paint materials and only about one hundred bucks of that is surface cleaner. So that being said, at that rate a gallon should last a home hobbyist a lifetime, so buy the right product for the job.
One reason we use so little is how we use it. Here in the San Francisco bay area with strict VOC rules we are not allowed to pour the surface cleaner out onto a rag. We have to spray it out of a spray bottle. Like most things we are forced to do, we resist. But it has turned out to be a great way to use this product. You should give it a try, it works real well. You spray the panel and then wipe it off.
I like to have lots of clean rags when I am doing paint work. Clean rags are one of the most important item you can have in a shop. In the last few years this has gotten much easier to do. I remember having a can of paint covered rags in the corner, thinking I could wash them. I would wash them and they would be clean but the dried paint on them would be hard and make the rags unusable. Then of course you don’t want to wash them in your home washer anyway, unless you want your wife’s bra to smell like enamel reducer.
Now a days the disposable rag is king. You can get a box of “rags” for a pretty fair price and just throw them way when done. You always have nice clean rags. They are not “just” paper towels, so don’t think that the “Mr. Cleanup” paper towels you get at the supermarket are going to do the job. Go to your paint store and get the real thing. There are many different kinds, from cheap wipes similar to your kitchen “paper towels” to lint free towels for final wiping. TORX products are available at NAPA auto parts and is one source for these towels. Again, yes they cost more money than washing rags or your wife’s “Mr. Cleanup” paper towels but what kind of money are you spending on your paint products?-----------------------------
By Brian Martin
They are commonly called “Wax and Grease Removers” but many manufactures have changed the name to “Surface Cleaners” or similar names. I think the biggest reason is because the name “Wax and grease remover” implies that they will actually clean all of the wax and grease off the surface. The other reason for a name change is the simple point that wax and grease are only a few of the contaminants that you battle against while painting.
The basic idea behind these cleaners is simple, they are designed to lift the contaminant up off the surface long enough for you to wipe it away. The surface MUST stay wet and HOLD those contaminants up in the cleaner for you to wipe off with a clean/dry rag. That is mistake most make, they let it dry and the contaminant ends up laying right back on the surface. First of all let’s clear up a few things; Lacquer thinner, acetone, MEK, and enamel or urethane reducers are NOT surface cleaners. Lacquer thinner evaporates too fast and doesn’t give you time to wipe it off wet. It is also much to strong a solvent for most cleaning and can get under the edges of sand thrus or soften substrates. Enamel and urethane reducers often have resins and other components in them that are designed to be added to the product they were INTENDED to be used with. To put it in a nutshell, buy and use the products recommended by the manufacture of the paint SYSTEM you are using. A gallon of the proper surface cleaner runs about twenty or twenty five dollars it is money well spent. The gallon will last you through many projects, a few cars even. The pint of paint or clear to do one small redo will cost more than that.
I checked on our paint dept. at work to see how much surface cleaner they go through. We do between 100 and 150 cars a month and purchase three to five gallons of surface cleaner. We purchase about $12,000 a month in paint materials and only about one hundred bucks of that is surface cleaner. So that being said, at that rate a gallon should last a home hobbyist a lifetime, so buy the right product for the job.
One reason we use so little is how we use it. Here in the San Francisco bay area with strict VOC rules we are not allowed to pour the surface cleaner out onto a rag. We have to spray it out of a spray bottle. Like most things we are forced to do, we resist. But it has turned out to be a great way to use this product. You should give it a try, it works real well. You spray the panel and then wipe it off.
I like to have lots of clean rags when I am doing paint work. Clean rags are one of the most important item you can have in a shop. In the last few years this has gotten much easier to do. I remember having a can of paint covered rags in the corner, thinking I could wash them. I would wash them and they would be clean but the dried paint on them would be hard and make the rags unusable. Then of course you don’t want to wash them in your home washer anyway, unless you want your wife’s bra to smell like enamel reducer.
Now a days the disposable rag is king. You can get a box of “rags” for a pretty fair price and just throw them way when done. You always have nice clean rags. They are not “just” paper towels, so don’t think that the “Mr. Cleanup” paper towels you get at the supermarket are going to do the job. Go to your paint store and get the real thing. There are many different kinds, from cheap wipes similar to your kitchen “paper towels” to lint free towels for final wiping. TORX products are available at NAPA auto parts and is one source for these towels. Again, yes they cost more money than washing rags or your wife’s “Mr. Cleanup” paper towels but what kind of money are you spending on your paint products?-----------------------------
So let’s go over exactly how you use it. As mentioned earlier, you need to keep it wet prior to wiping it off. The best way to do this is keeping your cleaning area down to a manageable size. I usually wipe no more than a half a panel at a time. About six square feet is all you can do without problems of it drying to fast, and even then you have to keep moving pretty fast. You just don’t want it to dry, if you do, you have wasted your time. You haven’t done what you intended to do, at all. It was not even close, you wasted your time.
When should you wipe the surface?
Well first of all, BEFORE you sand. If you don’t wipe the surface before you sand you will not sand off the contaminants, you will sand them INTO the surface. So a good cleaning before sanding is recommended. If the surface is really dirty, clean it a few times changing to clean rags every time. Remember, you want to wipe off the contaminants, so if you use the same rags on the subsequent wipes you can leave the contaminants you wiped off on the first wipe!
Wiping before applying primer or paint of course is also recommended. Broom and/or blow off the sanding dust (I have bench brooms for wood working that are fine bristled and work great). Be sure to use the proper cleaner and wipe it dry really well. Then be sure that any remainder has flashed off (evaporated) before applying your primer or paint. You don’t want any of the cleaner to be trapped under your primer or paint!
Have a few rags ready to go folded in fourths. Put the rag over the opening on the can of surface cleaner and give the can a “slosh” getting the rag wet, not too wet but wet. You don’t need to have it dripping all over the floor, but it should be good and wet. Get in the habit of wiping things down like you are painting it. Use a back and forth pattern with an over lap being sure to wet EVERY square inch. The entire area should be shiny wet, then switch to a clean dry rag and wipe it dry using the same “get every inch” procedure. If you feel it dried before you could get it off, repeat the cleaning. As a painter I worked under many years ago would make me repeat like a private in boot camp “YOU CAN NEVER GET A CAR TOO CLEAN, SIR”
Because the term “wax and grease remover” is thrown around so much little is said about the how different they can be. Until I had became a paint rep I didn’t even know there were different kinds. After painting for twenty years I had always just grabbed the “wax and grease remover” without a thought as to what I was using it on. When I bought a cleaner and found it worked different I just attributed it to the brand and not the fact that it was just not the type of cleaner I had been using.
Just like solvents you add to your paint products there are different “temps” cleaners. Not that they are to be used in different temp shops but that they flash faster or slower than another. This is important in that you don’t need a super slow flashing cleaner on your final wipe. Nor do you need a super fast one when you are doing your first wipe down of a greasy car prior to sanding.
There are also different “strengths” of cleaners. Some are designed for cleaning soft substrates like lacquer while others are much more harsh for cleaning enamel substrates. Most all of them “can” be used at most times but, there are some that are better than others for particular circumstances.
There are four common groups. I don’t have every cleaner listed here but this will give you a good idea at what is available.
1. A very slow evaporating cleaner. It is also very weak, and actually only mineral spirits or mostly mineral spirits. This does NOT mean you can go to the hardware store and buy their mineral spirits, for goodness sakes just but the high grade product from the paint manufacture. This is the type of cleaner is the most common found in the shop. It is a good cleaner because it is weak and will not attack any soft substrates like lacquer, uncured enamels, etc. But it will not clean a lot of strong contaminants like vinyl treatments. When you have a reason to believe there is a particularly bad contaminant you may need to go to a stronger cleaner. It is very slow evaporating so you have to be sure it is fully evaporated after wiping before you apply any paint product over it. Specifically those nooks and crannies, be sure it is good and gone before you apply any paint product. It gives you lots of time to wipe it off because it evaporates so slow.
Examples are:
Sherwin Williams R1K213, Martin Senour 6387, PPG DX330, DuPont 3939S, BASF 901.
2. This cleaner is fast and strong. It is commonly recommended as a “pre-cleaner” before sanding. It will attack some soft substrates like lacquer and uncured enamel but if you are using it before sanding you can correct that. It will clean the stronger contaminants like tar and unseen ones like silicone vinyl protectants.
Examples are:
Sherwin Williams R7K156, Martin Senour 6383, PPG DX440, DuPont 3919S, BASF 900.
3. This cleaner is a weak solvent with fast evaporation and is usually used just prior to painting, while the car is in the booth. It is very fast evaporating and is necessary in the production shop where you don’t have the time to wait for a cleaner like #1 to evaporate. It is perfect for this use, just getting those finger prints and dust residue off.
Examples are:
Sherwin Williams R7K158, Martin Senour 6384, PPG DX30, DuPont 3901S, BASF 901.
4. Because of VOC rules a waterborne solvent cleaner was developed. It is not needed in most of the country but it has been found to have an interesting use there. Because it has water in it (water and alcohol molecules share a common atom so they are a “link” between the water and enamel based solvents) it actually helps with static electricity. Washing the car with water is the best, but that can’t always be done.
It is also the recommended surface cleaner for plastic parts with many paint systems.
Examples are:
Sherwin Williams W4K157, Martin Senour 6388, PPG DX380, DuPont 3909 or 3949, BASF 905.
If you find that you have been using the “wrong” cleaner, don’t sweat it, it is not THAT critical. As I said, there are cleaners that work better than others in certain circumstances but few would be “wrong”.
I know of one particular mistake I made for many years. I was using one from the number 1 example. I used it all the time as I still do. The problem was I was using it wrong. Back in the days of lacquer primers and paint I had a few problems that I just couldn’t figure out, till years later that is. I would see a lacquer paint job I did a year or so later and there would be water spots on it, coming from under or within the paint. It looked just like you would have when you dry a car in the sun and the water would dry in the patterns that the wet towel left. I always knew it was the surface cleaner but just couldn’t figure out why it would happen. I now know that the cleaner was just too slow evaporating and some stayed on the surface to be buried under the paint. The lacquer primer soaked it up and held it. If I had waited a little while longer before painting or used one from the number 3 example I wouldn’t have had a problem.
Hopefully this info will help you choose the best cleaner for the job. But most off all, I hope it puts to rest all the “old husbands tales” of using thinner or enamel reducers as cleaners.
-----------------
When should you wipe the surface?
Well first of all, BEFORE you sand. If you don’t wipe the surface before you sand you will not sand off the contaminants, you will sand them INTO the surface. So a good cleaning before sanding is recommended. If the surface is really dirty, clean it a few times changing to clean rags every time. Remember, you want to wipe off the contaminants, so if you use the same rags on the subsequent wipes you can leave the contaminants you wiped off on the first wipe!
Wiping before applying primer or paint of course is also recommended. Broom and/or blow off the sanding dust (I have bench brooms for wood working that are fine bristled and work great). Be sure to use the proper cleaner and wipe it dry really well. Then be sure that any remainder has flashed off (evaporated) before applying your primer or paint. You don’t want any of the cleaner to be trapped under your primer or paint!
Have a few rags ready to go folded in fourths. Put the rag over the opening on the can of surface cleaner and give the can a “slosh” getting the rag wet, not too wet but wet. You don’t need to have it dripping all over the floor, but it should be good and wet. Get in the habit of wiping things down like you are painting it. Use a back and forth pattern with an over lap being sure to wet EVERY square inch. The entire area should be shiny wet, then switch to a clean dry rag and wipe it dry using the same “get every inch” procedure. If you feel it dried before you could get it off, repeat the cleaning. As a painter I worked under many years ago would make me repeat like a private in boot camp “YOU CAN NEVER GET A CAR TOO CLEAN, SIR”
Because the term “wax and grease remover” is thrown around so much little is said about the how different they can be. Until I had became a paint rep I didn’t even know there were different kinds. After painting for twenty years I had always just grabbed the “wax and grease remover” without a thought as to what I was using it on. When I bought a cleaner and found it worked different I just attributed it to the brand and not the fact that it was just not the type of cleaner I had been using.
Just like solvents you add to your paint products there are different “temps” cleaners. Not that they are to be used in different temp shops but that they flash faster or slower than another. This is important in that you don’t need a super slow flashing cleaner on your final wipe. Nor do you need a super fast one when you are doing your first wipe down of a greasy car prior to sanding.
There are also different “strengths” of cleaners. Some are designed for cleaning soft substrates like lacquer while others are much more harsh for cleaning enamel substrates. Most all of them “can” be used at most times but, there are some that are better than others for particular circumstances.
There are four common groups. I don’t have every cleaner listed here but this will give you a good idea at what is available.
1. A very slow evaporating cleaner. It is also very weak, and actually only mineral spirits or mostly mineral spirits. This does NOT mean you can go to the hardware store and buy their mineral spirits, for goodness sakes just but the high grade product from the paint manufacture. This is the type of cleaner is the most common found in the shop. It is a good cleaner because it is weak and will not attack any soft substrates like lacquer, uncured enamels, etc. But it will not clean a lot of strong contaminants like vinyl treatments. When you have a reason to believe there is a particularly bad contaminant you may need to go to a stronger cleaner. It is very slow evaporating so you have to be sure it is fully evaporated after wiping before you apply any paint product over it. Specifically those nooks and crannies, be sure it is good and gone before you apply any paint product. It gives you lots of time to wipe it off because it evaporates so slow.
Examples are:
Sherwin Williams R1K213, Martin Senour 6387, PPG DX330, DuPont 3939S, BASF 901.
2. This cleaner is fast and strong. It is commonly recommended as a “pre-cleaner” before sanding. It will attack some soft substrates like lacquer and uncured enamel but if you are using it before sanding you can correct that. It will clean the stronger contaminants like tar and unseen ones like silicone vinyl protectants.
Examples are:
Sherwin Williams R7K156, Martin Senour 6383, PPG DX440, DuPont 3919S, BASF 900.
3. This cleaner is a weak solvent with fast evaporation and is usually used just prior to painting, while the car is in the booth. It is very fast evaporating and is necessary in the production shop where you don’t have the time to wait for a cleaner like #1 to evaporate. It is perfect for this use, just getting those finger prints and dust residue off.
Examples are:
Sherwin Williams R7K158, Martin Senour 6384, PPG DX30, DuPont 3901S, BASF 901.
4. Because of VOC rules a waterborne solvent cleaner was developed. It is not needed in most of the country but it has been found to have an interesting use there. Because it has water in it (water and alcohol molecules share a common atom so they are a “link” between the water and enamel based solvents) it actually helps with static electricity. Washing the car with water is the best, but that can’t always be done.
It is also the recommended surface cleaner for plastic parts with many paint systems.
Examples are:
Sherwin Williams W4K157, Martin Senour 6388, PPG DX380, DuPont 3909 or 3949, BASF 905.
If you find that you have been using the “wrong” cleaner, don’t sweat it, it is not THAT critical. As I said, there are cleaners that work better than others in certain circumstances but few would be “wrong”.
I know of one particular mistake I made for many years. I was using one from the number 1 example. I used it all the time as I still do. The problem was I was using it wrong. Back in the days of lacquer primers and paint I had a few problems that I just couldn’t figure out, till years later that is. I would see a lacquer paint job I did a year or so later and there would be water spots on it, coming from under or within the paint. It looked just like you would have when you dry a car in the sun and the water would dry in the patterns that the wet towel left. I always knew it was the surface cleaner but just couldn’t figure out why it would happen. I now know that the cleaner was just too slow evaporating and some stayed on the surface to be buried under the paint. The lacquer primer soaked it up and held it. If I had waited a little while longer before painting or used one from the number 3 example I wouldn’t have had a problem.
Hopefully this info will help you choose the best cleaner for the job. But most off all, I hope it puts to rest all the “old husbands tales” of using thinner or enamel reducers as cleaners.
-----------------
Spray technique
By Brian Martin
A perfect paint job would have a consistent thickness on every square inch of the car, agreed?
To have four coats on the left fender, two on the right, five on the left door and one on the right wouldn’t be right. For consistent color, appearance, and durability you need the thickness (film build) to be consistent.
The closer to a perfect “decal” over the car, the better. However, just by the nature of human beings and their faults this isn’t always the case. If you were to check the “MIL” thickness (there are super accurate digital tools for this) of the average repainted car you would find many different amounts of film build.
More film build is usually found at the meeting point of two panels, like the seam at the door and fender. Think about it, you can’t paint down the whole side of the car in one pass, so you paint the fender with a number of passes of the gun starting at the front top, ending at the rear top, then moving down to the next pass right below that. You do this over and over until the fender is shot. Then you move on to the door, right? What happens right at the seam between the two? You have painted a coat on the fender, AND on the door; you can’t start and stop perfectly at the seam, so right there at that seam you are applying twice the amount of paint. Yep, if you apply three coats on the car, you are applying SIX coats at those seams.
It is very in these days of high solids clears to see a sag running vertically right on the edge of these panels. It will almost look like the panel has a body line going down the folded edge. It is caused by too much film build. Many times this sag isn’t repaired because it almost looks natural there on the edge. But it can be eliminated with a change in spray technique.
Ever seen a candy paint job that is darker at the seams? This was caused be the very thing I just described.
A classic example of this can be found on many early VW bugs. The hood is triangle shaped, with the front right at the handle being much narrower than the rear. Well, if you paint one side of the hood and then move to the other side it is VERY easy to end up with twice the coats right down at front of the hood. Go look at that point the next time you see an old air cooled bug and you will likely see a sag in the paint right at the bottom of the body line next to the handle.
Understand, this isn’t the end of the world. Most of the time this small discrepancy is acceptable. My point is, the closer to perfect, the better.
I was taught this simple spray technique about a hundred years ago (seems like that) at one of my first jobs. We were shooting lacquer completes. Sometimes these paint jobs had fifteen or twenty coats of color applied. My mentor at the shop pointed out to me to “Move the dry spot around”. If you didn’t you would end up with a much drier area at each of these seams. Remember, this was lacquer, if you have not shot it, it dried FAST. The overspray off the end of the spray pattern could produce a LOT of dryness. So if you did this coat after coat it would build up pretty bad.
After shooting a zillion coats of lacquer that way, I continued the practice. I have used this technique all these years with primers, sealers, colors, and clears, urethanes, epoxies, enamels, all with great success. It just makes sense to me to try to get that perfect “decal” over the panels. I pay particular attention to doing this when I do edges, there is one pet peeve of mine, one thing that boils my blood is seeing fender edges under the wheel well with dry spots or worse yet, no paint! EVERY SINGLE SQUARE INCH of panel should have good coverage. I don’t care if it is going to be hidden with a bumper, under a vinyl top, unseen after the fender or what ever is bolted on, I don’t care, EVERY SINGLE SQUARE INCH gets covered, if it was intended to be so.
Here is an example of the technique. You don’t have to do exactly as I have in the drawings, these are just suggestions. Adjust this concept to your particular needs. The basic point is to not start and stop at the same point every coat.
PLEASE NOTE: The direction of the lines in the drawing DO NOT mean you are to spray the paint in that angle, that was only done to more clearly show the starting and stopping points. To spray in this fashion isn’t out of the question though; I will find myself doing that as well, to get a more even coat. But that is only in particular places with particular needs.
I hope Brian doesn't get mad at me for posting his stuff. I hope this helps.
By Brian Martin
A perfect paint job would have a consistent thickness on every square inch of the car, agreed?
To have four coats on the left fender, two on the right, five on the left door and one on the right wouldn’t be right. For consistent color, appearance, and durability you need the thickness (film build) to be consistent.
The closer to a perfect “decal” over the car, the better. However, just by the nature of human beings and their faults this isn’t always the case. If you were to check the “MIL” thickness (there are super accurate digital tools for this) of the average repainted car you would find many different amounts of film build.
More film build is usually found at the meeting point of two panels, like the seam at the door and fender. Think about it, you can’t paint down the whole side of the car in one pass, so you paint the fender with a number of passes of the gun starting at the front top, ending at the rear top, then moving down to the next pass right below that. You do this over and over until the fender is shot. Then you move on to the door, right? What happens right at the seam between the two? You have painted a coat on the fender, AND on the door; you can’t start and stop perfectly at the seam, so right there at that seam you are applying twice the amount of paint. Yep, if you apply three coats on the car, you are applying SIX coats at those seams.
It is very in these days of high solids clears to see a sag running vertically right on the edge of these panels. It will almost look like the panel has a body line going down the folded edge. It is caused by too much film build. Many times this sag isn’t repaired because it almost looks natural there on the edge. But it can be eliminated with a change in spray technique.
Ever seen a candy paint job that is darker at the seams? This was caused be the very thing I just described.
A classic example of this can be found on many early VW bugs. The hood is triangle shaped, with the front right at the handle being much narrower than the rear. Well, if you paint one side of the hood and then move to the other side it is VERY easy to end up with twice the coats right down at front of the hood. Go look at that point the next time you see an old air cooled bug and you will likely see a sag in the paint right at the bottom of the body line next to the handle.
Understand, this isn’t the end of the world. Most of the time this small discrepancy is acceptable. My point is, the closer to perfect, the better.
I was taught this simple spray technique about a hundred years ago (seems like that) at one of my first jobs. We were shooting lacquer completes. Sometimes these paint jobs had fifteen or twenty coats of color applied. My mentor at the shop pointed out to me to “Move the dry spot around”. If you didn’t you would end up with a much drier area at each of these seams. Remember, this was lacquer, if you have not shot it, it dried FAST. The overspray off the end of the spray pattern could produce a LOT of dryness. So if you did this coat after coat it would build up pretty bad.
After shooting a zillion coats of lacquer that way, I continued the practice. I have used this technique all these years with primers, sealers, colors, and clears, urethanes, epoxies, enamels, all with great success. It just makes sense to me to try to get that perfect “decal” over the panels. I pay particular attention to doing this when I do edges, there is one pet peeve of mine, one thing that boils my blood is seeing fender edges under the wheel well with dry spots or worse yet, no paint! EVERY SINGLE SQUARE INCH of panel should have good coverage. I don’t care if it is going to be hidden with a bumper, under a vinyl top, unseen after the fender or what ever is bolted on, I don’t care, EVERY SINGLE SQUARE INCH gets covered, if it was intended to be so.
Here is an example of the technique. You don’t have to do exactly as I have in the drawings, these are just suggestions. Adjust this concept to your particular needs. The basic point is to not start and stop at the same point every coat.
PLEASE NOTE: The direction of the lines in the drawing DO NOT mean you are to spray the paint in that angle, that was only done to more clearly show the starting and stopping points. To spray in this fashion isn’t out of the question though; I will find myself doing that as well, to get a more even coat. But that is only in particular places with particular needs.
I hope Brian doesn't get mad at me for posting his stuff. I hope this helps.
1 - 11 of 11 Posts
