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Old 05-31-2009, 08:26 PM
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Short guide on tips and viscosity.

Iíve been reading some of the posts on this forum where many of you have been having problems with your finishes. Rather than trying to answer or troubleshoot any one post, Iíve decided to provide a general quick to guide for reference. First, let me give you a little background on myself.

Iíve been working on cars since I was seven years old and am now fifty-four. Started with mechanics and phased into body and paint in my early teens. Mostly because the work I seen others doing was, in my opinion, less than desirable. It took me about five years to perfect my painting skills and I became known as the King of Blending .

When I first started painting, we were using straight lacquer. Then the EPA banned all lead based paint and we had to use acrylic lacquer. I for one hated this acrylic based paint because it produced a hard brittle finish that would chip and peel, as the body would flex under normal driving conditions. It would be more evident on Corvettes and show as spider cracks in the paint.

Then Dupont came out with a clearcoat urethane system. What a nightmare, never cured after application and was Hell to apply. I attempted two jobs with this stuff and had to finish both with straight enamel. I wasnít the only one having problems and Dupont finally recalled it and came out with a new formula. Since then theyíve made other changes in the formula.

As you can see Iíve been doing this for some time. Many of you are novices and some arenít. For those that arenít novices much of what I write will ring a bell and to some it wonít, depending on skill level and quality of workmanship. Everyone has an opinion and very few are the same although they will agree in some generality. Thatís what this is for, to provide a general base for the novice to refer to and have some base to work from.

First, letís discuss spray guns. There are many to choose from. I see most of you are opting for the Harbor Freight models. Okay, youíre going on the cheap. For most of you thatís probably a good choice to start. As you improve and move on to a more expensive gun you still have future primer gun available. I consider these guns as nothing more than affordable primer guns myself as well as those sold at Walmart, Lowes, Advance Auto Parts, etc.

Better guns can be purchased from your auto paint jobber for between $125.00 and $200.00. They include name brands such as Sharp, Binks, and Devilbiss. There are other brands out there, but they fall short to my personal standard for finishes. The gun you chose will depend, after all, on you. All will do an adequate job for whatever your skill level is.

So now youíre asking yourself if it really doesnít matter what gun you have what is he trying to say. Well Iím getting to that. Take a break and go get yourself a cup of coffee like Iím doing and come back for more. Go on -get it. Iíll be here when you get back.

What weíre going to address is fluid tips and viscosity. The novice has no idea what fluid tip to use or the differences between them. The difference is the atomization for each size and what material youíre going to apply to what surface. There is a difference and you should adjust your viscosity of the material accordingly.

First, all detail guns utilize a 1.0 fluid tip regardless of manufacturer or cost. These provide a vey fine atomization and should be aware to setting your viscosity low. Lowering viscosity consists of nothing more than thinning your paint material to get the proper finish you desire. If youíre getting a lot of orange peel then your viscosity is too high. Thin it down some. If youíre too dry, youíve thinned it too much and your viscosity is too low.

For general purposes, I found early on, it would be wiser to start with a low viscosity and correct it as I go. Orange peel is more labor intensive to correct when it comes to water sanding afterwards. I despise heavy water sanding to correct a finish before buffing. Thatís why I donít follow other painters. My philosophy is; you put it on there, you correct it. Then maybe, just maybe, youíll learn or look for another trade.

As far as detail guns go, theyíre just good for striping and maybe for that small blend job in a door or trunk jam. Other than that, Iíve found very little use for them. I just threw detail guns in here so I wouldnít have to address it later.

Now youíre saying, what he is talking about viscosity. I read the can and it doesnít tell me to do what heís telling me. The manufacturer says otherwise. Yes, youíre right. The can doesnít tell you what I just did. However, that can youíre reading really isnít the spec sheet for that product and if you read other cans from other manufacturers, you will discover the instructions are nothing more than a generic recipe for failure for the novice. That isnít to say those instructions should be disregarded, theyíre not. When it comes to mixing the catalyst to paint ratio on enamels and urethanes theyíre pretty much right on. However, I donít know what lab vacuum or atmospheric pressure they operate at to achieve their finishes but here on planet Earth in the geographic area of upstate NY it doesnít work.

This is where Iím going to lose a lot of you. Youíre going to be stuck with the manufactures instructions on the can. Thatís okay, go for it. When you do finally get fed up with all that extra water sanding or worst yet, following someone else who thinks heís a great painter youíll be back to try something new.

Spray guns will vary in general in fluid tip sizes as mentioned above. They go from 1.2 to 2.5 I believe and will vary in size available from gun and manufacturer. In other words, some guns will be limited to what size fluid tip is available depending on purpose of use and manufacturer. For auto painting fluid tips will run from 1.2 to 1.8 max.

Generally, 1.6 to 1.8 tips are used for high build primers, filler primers and epoxy primers as they provide more material flow. For regular primers fluid tips 1.4 to 1.6 are generally used as the user doesnít require or desire a high build. That isnít to say these numbers are written in stone. No matter what primer you use you can use any of the above tips. Just be aware that if youíre looking for a high build then you should be using one of the larger tips. If youíre getting ready for paint you may want to back the high build off and use a smaller tip. Just remember to adjust your viscosity to what youíre trying to accomplish.

For painting you should have a separate gun. It should be kept clean at all times regardless of how inexpensive it is. This is your main tool and the lifeblood of your lively hood. Treat it with the respect it deserves and it will reward you in return.

Here tips 1.2 to 1.5 are used. Tips 1.2 and 1.3 are generally used for pearl paints. Not that larger tips canít be used itís these tips provide better atomization for the pearl effect. For metallics and base coat, tips 1.2 to 1.4 are used. Again, larger tips can be used; however, the flow of metallics may suffer as a result. Much will have to do with the quality of the gun and whether itís been maintained properly.

While Iím on the subject of metallics I want to address something. Before you start painting you should take time to discharge any static electricity that has built up on that body. It can and will play havoc on the flow of metallics and pearls if youíre not careful. Yes, Iíve experienced it. There are a few ways to discharge it. One way is drape a chain over the axle and let it touch across the floor a short distance. Another is to attach a wire to some exposed metal on the car to any exposed water pipe that may be present, or some other grounding source available.

As for non-metallics, enamels and urethanes tips 1.4 and 1.5 are recommended and most guns on the market are readily available with these tips. As you can see there really isnít any set formula to which tip to use only a general guide to go by. Everyoneís different in their opinion. However, regardless of what tips youíre using adjust your viscosity for the finish you want.

If you have any questions please feel free to ask.

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Old 05-31-2009, 08:28 PM
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Welcome, My god what a first post i will read it all. Cole
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Old 05-31-2009, 11:23 PM
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Yes, welcome. You will be getting plenty of disagreement from me about FOLLOWING THE DIRECTIONS ON THE TECH SHEET. That is my mantra and I will stick to it.

FOLLOW THE DIRECTIONS ON THE TECH SHEET will by the odds give you a better job. I do so EVERY TIME and it works for me! I mix every single thing EXACTLY to the manufactures recommendations, using a proper mixing cup and it works every time!

Proper tip size, with proper air pressure and most important proper VOLUME of air (CFM) and exact mixing directions and you WILL get the product to perform as it is intended by the manufacturer. PERIOD, END OF STORY.

Brian
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Old 06-01-2009, 09:59 AM
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Thanks for the welcome, it's like I said most of you will disagree with following the manufacturers directions. However, I like my paint to flow on with a smooth finish without alot of heavy wet sanding before buffing.

For the record, the manufacturers directions aren't the mantra, just the guide lines. But you do as you prefer.
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Old 06-01-2009, 12:00 PM
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If the gun is set up properly with the proper CFM at the gun the products will lay down properly.

Adding solvents can cause many more problems than a little texture. If you are experianced and have over the years worked around mixing ratios and are successful, credit your years of experiance.

To expect a newbe to start playing junior chemist is asking for trouble.

FOLLOW THE TECH SHEETS!!!!

Brian
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Old 06-01-2009, 01:45 PM
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Brian is right.
Paint Mfg's spend a lot of money on research to make their products
give the best results. They want you to get the best results with
their products, and know what works the best.
If you can't get good results following their instructions,
you're doing something seriously wrong.
Like the old saying goes,
"When all else fails-read the instructions"
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Old 06-01-2009, 02:57 PM
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Hi, I recently tried to blend clear on a spot repair and ended up with large droplets of clear as I tried to blend it instead of the atomization I was expecting. The tech sheet says 1.4 tip, nothing smaller, but if I went down to 1.3 or 1.2, would it blend better?
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Old 06-01-2009, 05:12 PM
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For the novice, the trick that would work best is to blend your basecoat, then shoot the whole fender, door, etc,, with clearcoat.
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Old 06-01-2009, 06:05 PM
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Quote:
Originally Posted by cjperotti
For the novice, the trick that would work best is to blend your basecoat, then shoot the whole fender, door, etc,, with clearcoat.

It was the rear quarter panel on a Ford excursion. To shoot the entire fender, that would of meant re-clearing 1/2 the truck. I understand that that is the normal procedure though, but I made an exception to keep it simple. I am just interested in what I could do to make the clear atomize better. I tried shooting reducer over the clear coat to try to smooth it out after spraying the clear and it helped a bit.
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Old 06-01-2009, 07:00 PM
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Sounds like you need more air pressure (psi)?
Or maybe reducing a little more.
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Old 06-01-2009, 07:14 PM
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Quote:
Originally Posted by Finaltheorem47
It was the rear quarter panel on a Ford excursion. To shoot the entire fender, that would of meant re-clearing 1/2 the truck. I understand that that is the normal procedure though, but I made an exception to keep it simple. I am just interested in what I could do to make the clear atomize better. I tried shooting reducer over the clear coat to try to smooth it out after spraying the clear and it helped a bit.
Preping and shooting the entire panel IS "keeping it simple". Believe me, there is a reason why that is the standard of the industry.

Brian

The Prius had a door skin changed on the rear door, blending both the front door, rocker and the quarter, up and over the roof rail.

The Honda Accord has a spot of primer on the quarter, but blending and clearing goes up and over the doors on the roof rail. No open blends, done deal.





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Old 06-01-2009, 07:42 PM
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Follow the spec sheet, works every time.

Vince

Last edited by 302 Z28; 06-02-2009 at 09:06 AM.
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Old 06-01-2009, 07:48 PM
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Okay, that's more information than previously provided and I was afraid youíd comeback with that. Also, I just reread your original post and misinterpreted what you were asking.

Whenever a mistake like that happens have a roll of paper towels and klix, prepsol or other type of dewaxer you maybe using handy. Use them to wash off that whole area you just painted right away before it dries. You have a short window of opportunity here. Donít worry about the primer underneath. No damage will occur to the primer or any repair work under it. This is for future reference.

In answer to you original question I would say yes. When I paint I donít use any tip larger than 1.3. Normally unless Iím painting a whole car, I plan on blending someplace.
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Old 06-02-2009, 08:18 AM
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Following the spec sheet, I can only combine the clear and the activator, it doesn't say anything about reducer, so I don't want to add any in fear of something reacting. I am using a Devilbiss Plus with 1.4 tip, 1.25 turns out at 45-50 psi.
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Old 06-02-2009, 08:34 AM
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It isn't that it is going to "react" some how, adding a little reducer isn't going to produce a catastrophic failure or something.

If the manufacturers mixing instructions don't include reducer it is because the reducer has already been added! There are many products that are "RTS" (Ready To Spray) and you simply pour it out of the can into the gun and spray it. JUST BECAUSE you normally add a reducer and this RTS doesn't tell you to doesn't mean you add it!

The product you are spraying has been designed to be sprayed as mixed. If you set up your gun properly and you have the proper air volume for the gun (CFM) it is going to perform as intended.

Adding extra reducer isn't going to make it blow up in your hands. HOWEVER, solvent, ("reducers") are the NUMBER ONE cause for failures. Be it die back (when the extra solvent leaves the film you have applied after it has begun to cure) soft film because the extra solvents inhibit the linking of molecules, to solvent pop, to runs, to wrinkling when the extra solvent soaks into the substrate.

Too much solvent is the NUMBER ONE reason for failure, PERIOD.

Can it be done with the right gun set up and spray technique? Sure it can, but again, following the manufacturers directions is better by the "odds" every time.

FOLLOW THE MANUFACTURERS RECOMMENDATIONS ON THE TECH SHEET!

Brian
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