Spraying Latex with a Conversion Gunby Lorenz Prem
I wanted to get into spray painting for a long time. The technique produces flat surfaces; the kind that are impossible to create with a paintbrush. The complexity of having to set up a gun and mixing the paint kept me from taking the plunge.
After months of research I finally pulled the trigger and purchased a system. Looking back it, I made an elephant out of a mouse. Spraying latex paint is easier than it looks. I hope the following guide will help you get started much faster than I did. Perfect surfaces are within the reach of even a first-timer.
Tools and Materials
Spraying beings with purchasing the materials and tools. There are a number of options for each item available. Any one tool will probably perform adequately. I present product names and links solely as a reference. The products I use perform, but do not necessarily represent the only or best option.
- Conversion Gun: A conversion gun, as the name implies, is a spray gun that can be powered by a traditional compressor (high pressure air source). The gun turns the compressor into a HVLP system (high volume low pressure). There are a myriad of gun styles available, each having benefits and drawbacks. The only necessary property a gun must have is the ability to spray latex (water based substances). This typically means you will be shopping for a gun with a large needle size (1.2mm or larger). I use a gun from the DeVilbiss Starting Line. As the name suggest, these guns are for new users. They perform well, but won't break the bank. Only purchase a gun with good reviews. Super cheap models sometimes cannot produce correct spray patterns; ever. Price, however, is not the only indicator of quality. Ask around.
- Compressor: The compressor itself is a totally unremarkable. All you need is a compressor powerful enough to supply your gun with air. Check the gun's requirement against that of your compressor. If your compressor is too small, you might run out of air in the middle of painting. That will cause the gun to stutter. It will spray large droplets of paint on your project. That's not what we want. Alternatively you can spray in burst and let your compressor catch up.
- Hose:You'll need a hose to get the air from the compressor to your gun. If you don't have one already, this thread might help you find a good one.
- Pressure regulator: The pressure regulator regulates the air pressure going into your gun. Having the regulator directly on your gun simplifies setting up the spray pattern. Just make the adjustment directly on your gun. Alternatively you can use the regulator on your compressor. Every compressor has one. I use the Ampro A1440 I reviewed here.
- Gun stand: A gun stand holds your gun in place during filling. It's just a piece of metal, but a very useful one. Any model will do.
- Paint Filter: Paint going into a spray gun should be filtered. Otherwise you risk clogging your gun during use. It's best to avoid the issue and invest in cheap paint filters.
- Respirator with organic filters: A respirators is critical for spraying latex. Do not spray without one. When spraying latex only about 60% of the paint makes it onto the project. The rest hangs in the air in the form a very fine mist. It is impossible to avoid breathing this mist without a respirator. I use the 3M 7500 respirator with organic filters. The setup removes all fumes from the air. You can read a full review here.
- Spraying hood or full body suit: Professional spray painters wear full body suits while doing their work. For small projects suits are not really necessary. A pair of old trousers, a long sleeve shirt, gloves, and a spray hood will do. Spraying paint will cover you head to toe in a fine mist. You'll color the surface of your shirt, but not much else. A spray suit is easier to get into and out of in a heavy use scenario. I use old clothes paired with a spray hood. I prefer not the color the little hair I have left.
- Painters plastic: Just as important as protecting yourself is protecting the area you spray in. If you are spraying a closet on one end of the room, the paint mist may travel all the way to the window on the other side. You must cover all surfaces in the room (except the ceiling) you do not want to paint with painters plastic. Most of the paint will settle on the floor, but there is no guarantee some might not end up on the walls. If you are spraying in your garage, set up a spray booth. Make sure to allow for circulation.
- Paint thinner/conditioner: Latex paint is too thick to be sprayed undiluted. Luckily latex paint can be thinned with plain water. Going one step further, I use Floetrol, a paint conditioner. Floetrol makes the paint set up slower, which helps with producing an even coat.
Thinning the paint
Application begins with thinning the paint. The internet is full of advice on what ratio to use. Truth be told, the correct ratio will depend on the paint you are using. It's unlikely you'll find the perfect ratio on a website. Trial and error are your best option.
Fortunately the ratio does not matter so much for the beginner. Slightly off mixtures will not result in catastrophe. Your gun's spray pattern might be smaller than it could be, or the paint will run a bit too much. These are all valid concerns, but none of them result in failure. You'll just have to work harder to get the finish on the project. Unless you are wildly off, you'll be able to finish the job.
My golden rule is: start by thinning the paint with Floetrol according to the recommendation on the can. If I use water, a 1/10 mixture of water to paint gets me in the ballpark. From there it's all about trial and error. Experiment with the correct ratio for your paint. Once you understand how your gun works, you'll better understand how the ratio affects things.
The gun settings will vary from gun to gun. You have three knobs to worry about: the regulator, the paint supply, and the gun's internal pressure. Set the regulator to ~25psi and close the other two valves completely. Slowly open the two closed valves one at a time. Spray a test pattern on a piece of cardboard. Repeat until you have found good pattern. The gun will usually have many settings at which it performs.
At first you'll be completely lost. In a few minutes however, you'll get a feel for your paint and gun. Adjust the settings until you get a reasonable spray pattern. "Reasonable" is the correct word here, because it might already be impossible to get the perfect spray pattern. Your paint mixture may be slightly off. Getting that right will come with experience. The "good enough" spray pattern will get you through the current project.
I could tell you my settings for spraying Behr paint diluted with Floetrol (25psi, full turn on airflow, 3 turns on paint supply), but it would not help you very much. These are gun specific. The insight you should take away is that it does not take very much time or skill to adequately configure your gun. Every time you do it, you'll get better and faster.
Spraying latex is an excellent way to learn how to spray. If you make a mistake, sand out the defects and cover the spot with another layer of paint. Latex touches up perfectly.
There are plenty f videos on the web that will teach you the right technique. I think these videos are more harmful than useful for the first-timer. It's too much information too soon. Getting a good consistent coat down is not very hard. You'll make mistakes, but you also don't have to go to school for a day to get the job done.
Just do it. Every journey begins with a first step.
I was very apprehensive about getting into spray painting because of gun cleanup. I was worried that cleaning the gun would take forever or that I would ruin the gun. The truth is that gun cleaning after spraying latex is easy. All it takes is water.
Latex paint is water based. Paint remnants can be removed from the gun using plain water. Disassemble the gun, rinse all parts, and you are done. Running water through the gun before disassembling it will speed up the cleaning process. It is, however, not necessary at all. A perfect job can be done using just a bucket of water.
Gun cleaning is so easy in fact, that I feel I don't need to explain it in detail. Don't worry about it. You'll get it right the first time.
Off course this post is just the beginning. What I hope I did is remove the doubt that keeps you from getting started. Spraying latex is not that difficult. Once you get started you can build your knowledge about the subject. Efficiency and superior results come from repletion and practice. Getting started spray painting is not as hard as it seems.