Spraying at home

[bluelighttaxidriver]

Looking at spraying my spitfire this summer. I appreciate that the best way is to have it done professionally, but budget & have a go attitude is winning.

Tying myself up in knots though. Which is better.. HVLP or LVLP spray guns (& why.?) . Also, would a 3hp 100ltr compressor be up to the job? Many thanks.

[Guest]

Hello.

 

If you are running a 100Ltr unit, then a HVLP gun is your best option and the best gun for spraying. The important factor is the free-air / cfm; which as you are spraying will be ample. It's only when you are using a "thirsty" air tool (i.e. sander etc.) do you need high cfm and a minimum of 100Ltr. 

 

LVLP are beneficial if you are using a compressor that has a very low cfm and these guns, due to their spray nozzle size & design, are used in the main for more intricate work where the paint delivery is slower and finer. 

 

Using a LVLP gun for complete car spray will take ages and be inefficient. Additionally the setting up of LVLP is a bit / lot trickier than HVLP. 

 

Stick with HVLP and you will be fine.

 

Regards.

 

Richard.

[Clive]

Have a look on the MIG welding forum. There is a section dedicated to painting that will be useful

 

My Spit was sprayed at home using a 3hp 50L compressor and came out well. I used 2k paint and an air fed mask.

Top tip is get some acrylic stopper

...

 

That aside, good extraction is vital, I used 2 car rad fans fitted into an open window with hardboard as a mounting board. And the garage was lined with poly sheet. Still plenty of bits got in the paint, but with effort it gets there in the end.

In terms of guns, a 1.3 nozzle hvlp gravity gun and a 0.8 hvlp touch up gun. The little one gave a better finish, but would take an age to do big areas. Useful for awkward bits, and the two guns cost a total of approx £30!

[bluelighttaxidriver]

That's both good advice, thanks. Do regularly look at the welding forum. It has been really useful through the welding stage of my build.

So could I get away with a 50ltr tank? Saves a little on money, which has already spiralled, as I'm sure everyone has experienced! (Hope the wife doesn't read this...!!) Also, what nozzle sizes are best for high build primer, & paint? Probably going to use cellulose, as the danger aspect of 2k at home concerns me. Thanks again.

Steve.

[68vitesse]

Sprayed my Vitesse with cellulose a few years ago, 3hp compressor and 50L tank direct drive twin cylinder but go for a 100L if budget permits. Give garage floor good vacuum and a spray with water to settle any dust before spraying.

Think 3hp is maximum you can run on a ring main depending on make also direct drive ones tend to give a higher free air delivery than belt drive.

 

Regards

 

Paul

[Clive]

There are some non-isocyanate 2kpaints about. I have no experience, nor knowledge. However, if reviews reckon it is OK I would use.that as the primer on the basis 2k barely sinks at all. Celly does, sometimes months after you finished. I have a t shirt...

 

I have a.belt.drive sip, paid £120 used, but not much. Sold my direct drive sip for £100, and the belt drive is MUCH quieter. But I have lent my compressor out to friends, as it doesn't get regular use. So may be asking about and see if you can borrow one?

[Guest]

Steve.

 

Rather than writing loads about your questions, I have pasted the following for you; it is an article which I keep for members in other car clubs who are in your similar situation. There is some extra info contained within which will be beneficial.

 

It's a good "starter for ten" and steers you in the correct direction.

 

An American article but very informative; of which I find most are. It speaks of 150Ltr unit but you do not need that for what you are doing and of course Americans always go BIG !!

 

Take specific note of spraying action - whole arm NOT wrist and also the need for a secondary gun for clear coating, if you will be doing that. 

 

It also covers cfm delivery; ideally you want 13cfm+

 

If you have a 100Ltr unit it will run longer without having to recharge as frequently as a 50Ltr unit. But to be honest a 50 unit will suffice for what you are doing just remember it will need to catch its breath more often. So do about 3 sweeps and then pause for the reservoir to recharge.  

 

Hope the following assists and certainly helped me to get started on the spraying jobs.

 

The last paragraph may be helpful explaining to your wife !!

 

Good luck.

 

Richard.

 

STARTER SPRAYING ADVICE

 

Every painter wants to turn out the best paint job possible. So what’s the key to a successful paint job?

A new spray gun, of course.

As a red-blooded American male, I just couldn’t resist. You can never have enough tools. Right guys?

Actually, a skillful painter with the correct spray gun (notice I said “correct,” not “new) is the right recipe for an outstanding paint job. But a spray gun is just like any other tool: It has to be matched to the job you’re doing.

(It’s also worth mentioning, even though it’s not part of this particular article, that a great paint job is almost impossible without proper surface preparation. See that article in the September issue of BSB.)

 

How Many Guns Do I Need?

Whether the gun is several years old or brand new, you have to take into consideration what material you’re spraying before you choose your gun.

Since the advent of VOC laws, the material you spray has changed too, so it’s even more critical to choose the spray gun based on what you’ll spray with it. For example, there are spray guns designed especially to spray clearcoats. Others are designed for primers and other heavy-bodied materials. Many painters also have a spray gun for primers and surfacers, another for basecoats and still another for clearcoats.

If you can afford to have three spray guns, this is the ideal scenario. At the very least, you should consider one spray gun dedicated to spraying only clearcoats. There’s nothing more disconcerting than laying down a beautiful finish and when you start to lay down the final coat of clear, a glob of basecoat comes out and lands right in the middle of the clear. Having a dedicated clearcoat gun will eliminate this from happening. Of course, you can have the same thing happen with a glob of old clear from your last job if you don’t clean your gun properly. (I’ll go into that in detail a little later.)

But don’t think you have to have three guns. I know painters who have one gun with a 1.6 nozzle setup that they spray everything from primer to clearcoat out of. But it takes a little more time and effort to thoroughly clean the gun before spraying a different material.

 

Choosing Nozzle Setups

So what nozzle setups should be used for which products? Actually, you’ll achieve the best results when you refer to the paint manufacturers technical data sheets for that particular product you’re spraying. They’ve thoroughly tested their products and identified the best needle nozzle combination for each product.

A general rule of thumb is:

• Heavy-bodied primers and primer surfacers work best when you use a nozzle size of 1.7 to 2.2.
• Basecoats should be sprayed with a 1.4 to 1.6 nozzle.
• Clearcoats should be sprayed with a 1.3 to 1.7 nozzle.
• Sealers and single-stage urethanes should be sprayed with 1.4 to 1.6 nozzles.

   

Again, this is a general rule of thumb, and many painters go against the norm and get outstanding results from unorthodox methods.

Generally when you have a high-solids clearcoat or single-stage urethane, you should go down in nozzle size to break the material down into smaller particles to get a smoother finish. But some spray gun manufacturers go against this rule and go up in size – so be sure to refer to the gun manufacturers recommendation as well as to the recommendation from the paint company.

Primer surfacers require a much larger fluid nozzle. Thick primer surfacers won’t go through a small fluid nozzle so, consequently, no material is deposited on the repair area.

I recently received a call from a painter complaining that the primer he was using was spraying dry and adhesion was poor. He was using a very high-build product, but he said his body work wasn’t being covered and the primer was flaking off.

I asked what fluid nozzle he was using, and he told me 1.3. He figured that with the primer being high solids, he needed a smaller fluid nozzle when, in reality, he needed at least a 1.7 nozzle.

Understanding product and what’s needed to apply that product is very important, and many times problems can be attributed to not being aware of the basic fundamentals of choosing proper equipment for the product you’re spraying.

 

Air Errors

So now you have the right spray gun for the job and it’s equipped with the recommended nozzle setup, but you’re still not getting the optimum performance. Many times, this happens after you buy a new spray gun, especially if it’s a different brand from the one you were using.

What does this have to do with it, you ask? Plenty!

Maybe you don’t have enough air to properly run your spray gun.

“Come on. Give me a break,” you say. “My compressor puts out over 150 PSI. How much air do you need?”

The fact of the matter is, PSI (pounds per square inch) doesn’t matter at all. The air consumption of a spray gun is measured by cubic feet per minute (CFM).

Air requirements for a spray gun can range from 2 or 3 CFM for a small touchup gun to as much as 18 CFM for some gravity-feed or siphon guns. The average for most popular guns is around 12.

If you check the output for most 5-hp compressors, it’s around 14 CFM max. Translated, this means that the average 5-hp compressor will efficiently run one spray gun of average air consumption. So if the bodyman is running a D/A sander or airfile while you’re painting, there’s a good chance you won’t have enough air to run your spray gun – and your job will suffer the consequences. Even though your spray gun may only use 30 PSI of air, it may exceed the CFM capacity of your compressor.

Other considerations are your air hose and fittings. If you’re using a 1/4-inch air hose, you’re severely hampering air flow and should consider at least a 3/8-inch inner-diameter air hose with high-flow couplers and fittings. This will dramatically improve air flow and efficiency.

Remember when you were a kid and you stuck a potato in the tailpipe of you buddy’s car, and it wouldn’t run properly? Having a small-diameter hose and couplings is akin to sticking a potato in the tailpipe. The gun is starving for air.

 

You Lean, You Clean

You knew I was going to get around to it. The next subject is cleaning. I know! I know! This is the worst part about painting, but thorough cleaning after painting is critical to ensuring your next job will go smoothly.

Most gun manufacturers include cleaning equipment with their spray guns, which usually consists of a round-barrel brush to clean the passages of the gun and the cup.

You need to remove the fluid needle and nozzle as well as the air cap after each use and thoroughly clean them. Flush the gun with fresh solvent after each use unless the material you sprayed was water-based, in which case, you should first flush and clean the gun with tap water, followed by gun-wash solvent.

Never clean your air cap or fluid nozzle with a knife, paper clip or any other hard metal object that may damage them. Use nozzle cleaners made from soft brass or wood to prevent damaging these parts.

 

How to Handle a Gun

The final step in achieving the best job possible is proper handling of the spray gun. Different painters have different techniques and operate at different speeds, but it’s important to hold the spray gun perpendicular to the surface of the car and to keep it at the proper distance.

Some painters don’t hold the gun perpendicular to the surface until they’ve passed the end of the panel. Toward the end of the panel, they tend to stop the gun and twist their wrist to point the gun to the end of the panel instead of moving their entire arm the length of the panel (much like a brush-stroke-type of method, as if they were painting with a brush). Because of this, the end of the panel does not receive the same even wet coat it would get from extending the gun the entire length of the panel.

Also, gone are the days when you could pour the reducer to your paint, hold the gun 12 to 14 inches or more from the surface and hose it on – since the reducer would allow the paint to flow and level.

But now, with HVLP technology, you need to hold the gun 6 to 8 inches from the surface to maintain control of the fan and of the material you’re spraying. This prevents dry spray and orange peel.

 

It’s a Guy Thing

OK, so maybe you want a new spray gun but don’t really need one. A little fine tuning to the one you have may well be all you need. And I’m sure your wife or girlfriend would think that money could be better spent at the mall or having dinner and a movie every weekend for a month or two.

They don’t understand. It’s a guy thing.

[bluelighttaxidriver]

Wow...! Thank you very much... :-)

[bluelighttaxidriver]

Watching Fast & Loud. He's not using an air fed mask whilst spraying. What paint do you think he's using...?

[pageste]

Just an aside from bitter personal experience, I got a friends son to spray my car in 2K . He ended up doing it 3 times and even now its not great. One of the issues was he sprayed it for the second time in my garage which is chock a block with spares and a cupboard full of lotions and potions. The finish dried with lots of pock marks and fissures. We showed it to a refinishing chap and he said it was caused by silicon contamination from the polishes in my cupboard. The 2K can pull it in from the atmosphere apparently. It was a case of 3rd time lucky when it was decontaminated away fronm the site and sprayed elsewhere to an acceptable standard.

 

 

see http://www.mig-welding.co.uk/paint-faults.htm  fisheyes