Buffing question ?

[Five Star]

looking at sherwin-automotive's website

If this is the paint your using

The correct mixture is 5 + 1 + 1

not 8 + 4 + 1

more reducer adds orange peel

Dimension Product Info

[NascarFool]

The Sherwin Williams tech said in Colorado the mixture of 8+4+1 (on the can it daoes say 5+1+1) is required for the altitude and by state code compliance. I am no pro and I'm willing to try almost anything to get a good paint finish. Today I did pick up some Meguiars 1000, 1500 and 2000 grit paper along with some buffing pads and terry towels. Hopefully I won't have to use much if things work out. I have come to the conclusion that my problem is me with the orange peel. I guess you could say there is a "loose screw behind the paint gun".

[Five Star]

I would try the 5 + 1 + 1 with the 3.5


Dimensions 5.0 uses 8 + 4 + 1

I logged into sherwin-automotive and there is no altitude adjustment listed.

If u still cant get it to work then maybe you could switch over to Dimensions 5.0 which actually uses the 8 + 4 + 1 mixture.

Seems everything else is ok, and I'm sure even if the guy behind the gun has a "loose screw" It has to do with the mix.

which # hardner are you using?.

[NascarFool]

The first time I used DH653 hardner with DR634 reducer. The last try I used DH654 hardner and DR633 reducer (the combos were recommended by Sherwin Williams). The dude at Sherwin Williams said that Colorado requires 8+4+1 on the mix. I have tried less reducer with the same results. I honestly think that I am moving the gun too fast across the surface being painted. Otherwise I'm not getting a good "wet" coat.

*EDIT*
I sent off an email to Sherwin Williams paint support. I should have an answer tomorrow.

[Five Star]

im pasting this article on setting up the gun, spray pattern and pressure, if thats how they mix it in colorado. then i dont know.


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! This 10 lbs at the cap is something you have no way to measure. “AT THE CAP” means at the fluid/air cap where the paint sprays out. It takes a special air cap with a gauge on it. This “test cap” is used by paint reps, air quality control agents but only a few painters. I have never seen on in a body shop. I say this because the instructions that come with many HVLP guns tell you to “adjust to 10 lbs at the cap” all the while they give you no way of measuring the cap pressure. There is usually a “MAX PRESSURE” stamped on the gun or in the instructions. This “max pressure” is the maximum pressure you can set the gun pressure and still keep the cap pressure at the 10 lbs max at the cap the law allows (in most VOC regulated areas where HVLP is required). So the VOLUME of air (CFM, Cubic Feet per Minute) is the key to proper atomization with an HVLP.

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 many urethanes and epoxies, or base coats the 1.3 or 1.5 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.

This however doesn’t mean I recommend a 1.3 tip for your primer gun. It is only meant to make the subject of atomization easier to understand. Always refer to the tech sheets of the particular product you are shooting to see what tip you should be using.

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! That balance of atomization and enough material coming out is what you are after.

Now, you’ll notice that I said, “raise the pressure to the gun”, while earlier I said to set it to manufactures specs. This can be anywhere from 25 lbs to 50 lbs. This gun manufactures “recommended pressure” is AT THE GUN. This means at the INLET of the gun, NOT at the cap and NOT at the other end of the hose, but AT THE GUN. If your gun doesn’t have a regulator on it, then install one. This regulator will tell you at all times what the pressure is AT THE GUN, which is what you need to know. Be sure to buy a quality regulator from a paint gun manufacture. Some cheapie regulators are going to rob air volume from your gun because of restrictions within them. This is something most home hobbyist CAN NOT afford do to small compressors. If you don’t have the air volume to atomize your paint, you are NOT going to get satisfactory results.

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!


article with spray pattern pics are here


Here


I only do touchups So i use a SATA Minijet BC/CC, this guy was having trouble with his clearcoat, but u can apply the settings to your single stage.. check out the whole thread its pretty informative

[NascarFool]

I'll read that again before I start spraying again. My gun came with a 1.5mm tip. Think I should get a 1.4mm or 1.3mm ? If I do, I'd have to order it because no one stocks it here.

[Five Star]

i couldnt tell you. i would think u could adjust the gun to where the 1.5 would work, but like i said i dont know about the effects in high altitudes. i'm just trying to throw some things out there for u to look at

[NascarFool]

I did get an email response from Sherwin Williams. They said to mix at 5+1+1 as shown in the DATA pdf file. Hopefully it will warm up enough to paint this weekend.

[Five Star]

ok.. let us know how it goes.

check the data pdf. use the right reducer for the temperature. as far as the hardner you'll probably use the 653

also go over that other link on setting your spray pattern

i think the pressure at the gun should be around 30 psi, but like i said I use a minijet.

set the pressure at the compressor higher, because of the pressure drop through the hose (use the shortest hose you can). plus with the higher altitude your gonna have a 35% drop anyway

[NascarFool]

*Update*
I did repaint the cab and doors last weekend. I mixed at 5+1+1 and set the air pressure at 90PSI at the comp and 45PSI at the gun. It looks real good but I'm a rookie and I'll still need to wetsand it to get the light orange peel out. The paint looks a ton better than the "textured" finish of the hood and fenders. I stripped the exterior of the bed down to bare metal but it isn't warm enough to prime it. Hopefully it'll warm up one last time before the snow flies. Thankfully there will be no bondo needed on the bed. Pics will be posted after it's completed.

[the other pc]

[papi_Jay]

Wow Nascar all that helping I did thru email and all it REALLY was is that the goofy guy at the store gave you the wrong ratios ?

[Mike Phillips]

Looking forward to the pictures of your results...

[NascarFool]

Originally posted by papi_Jay
Wow Nascar all that helping I did thru email and all it REALLY was is that the goofy guy at the store gave you the wrong ratios ?

Yep, I plan to call them tomorrow and chew some butt. I sent my son to pick up 3 quarts of paint and enough reducer and hardner to repaint. The bone head sent me 3 quarts of paint, 1 gallon of reducer and 1 quart of hardner. He should have sent a pint of reducer and a pint of hardner. Your help was greatly apprecitated too !

*Edit*
A pint of each may have been to little and a quart too much. A gallon is over kill. I guess I can use the reducer to wipe down the bed before I prime it up.

[papi_Jay]

You should have informed sherwin williams of how much paint you have wasted and asked them to contact the store to compensate you by replacing it really .
If one of their employess misinforms , it is their fault and that store / employee is liable .
I told you everyone is telling you bad things about how to paint , I just never imagined the guy at the store would be on that list as well ..

Hope it comes out pretty !

P.S. Make sure you knock the coats you have already layed completely flat ( no gloss , no OP ) with 400 grit wet 1st . Then clean up with a good soap n water , then degreaser prep spray .
Only lay maybe 2-3 full coats , let it dry an hour or so IF there is no orange peel , then spray one last " flow coat " .
If there is orange peel , final sand with 1000 grit to knock it flat , then your flow coat after cleaned up and dry .
Flow coat is a final coat of paint OVER reduced by %15 . It dries slower , so let it sit a week before doing any polishing . It lays much smoother though , and minimal wet sanding with 1500-2000 will be needed to knock it flat .
It should look like an OEM finish orange peel or REALLY glass smooth though without wetsanding .