A Beginner’s In-Depth Guide to Professional Paint Results
Charlie’s Preamble
It is no secret that we love powder-coated products at Yellow Weld and only use aerosol paint when necessary. However, as someone that has spent much of my life using aerosol paints in the hobby as well as professional settings I have a deep-rooted love for spray painting, airbrushing, and using HVLP guns to get a high-quality paint finish. As I finish up a project that needed multiple spray paint colors, the idea for this article dawned on me. I will type out a step-by-step guide to achieving high-quality paint results.
“Charlie, what makes you such an expert in this field?” Well, dear reader, I have been spray painting since my rebellious high school years, airbrushing for just shy of a decade now, and have painted many personal projects with aerosol paints. But the real experience comes from my stint doing time at a local Columbus sign shop. We made high-end signs and painted them to high-end standards. My manager taught me his eagle-eye abilities to feel if a paint mix is too thick or thin based on how it sits in a cup, how to dial in every aspect of an HVLP spray gun using homemade jigs, and the split second you know you’ve ruined an entire paint job in the first 2 minutes of spraying. If we had a single run in a 20 square foot sign we sanded everything off completely and restarted. Too many dust particles landing in the wet paint overnight meant we were starting the project over. If the paint was just a hair shinier than a semi-gloss finish we would- yep, you guess it- sand it down and try again. I have been through the boot camp of paint finishes and can walk away from it giving you good advice on steps to follow (as well as which steps you can glaze over because they are completely unnecessary.)
Step 1: Prepping for painting
We must crawl before we can sprint. The preparation is simultaneously the least fun and the most important step to achieving a good paint finish.
Sanding
Sand your workpiece with fine-grit sandpaper (120 grit at the very minimum.) It is quick and easy to hit your piece with 40 grit sandpaper and blast it with spray paint, however, heavy grit sandpaper leaves deep grooves and gouges in your workpiece.
You will want to start with a heavy grit, such as 36 or 40 grit to remove any irregularities in material or preexisting paint on your workpiece. Then, step it up to 80 or 100 grit to smooth out those deep scratches you just created in the workpiece. Finally, hit that bad bitch with some 120 grit sandpaper all over to blend out any remaining scratches and you’re good to go. (I like to take my work up to 220 or even 320 grit sandpaper, but oftentimes call it “good enough” at 120 grit because I’m impatient and eager to paint by the time sanding is finished.)
Once your scratches and deep grooves are worked out you’re ready to move away from sandpaper.
Clean up the Dust
The next step is to get rid of all the particulate matter you just created by sanding your workpiece nicely and smoothly. My first go-to for cleanup is using a dry rag along with compressed air (or canned air if your air compressor is broken like mine is.) Quickly run over the whole piece with a dusting rag while blowing off any small particles you see.
Now you’re going to want to grab your tack cloth (wearing gloves of course, as those buggers are coated in adhesive and leave your hands feeling gross). Tack cloths are sticky, perforated rags that are specifically designed to clean things, namely metal, before painting. You can find a tack cloth for no more than $1 at any Sherwin Williams Auto Body paint store, or similar auto paint supply store. One tack cloth should last you for at least a dozen projects depending on the size of your workpieces, so it is worth picking up 5 or so tack cloths if you will be painting fairly frequently.
Wipe ‘er down
Grab a fresh rag (not your dusting rag) and a bottle of your favorite scented industrial cleaner. I always prefer the high of huffing acetone because denatured alcohol smells funny, and I can literally feel xylene melting my brain when I use it. I kid, I kid. The first step in this round is to pop on your respirator and some clean latex gloves.
You’ll want your stripper of choice in a small cup (denatured alcohol, mineral spirits, xylene, or acetone to recommend a few). Go ahead and soak your clean rag and wipe down every single square inch you can get that rag into. Anything in this family of chemicals evaporates when exposed to oxygen so you can go heavy on the cleaning and not have to sop up any liquids when you’re too heavy-handed. But better yet, this family of chemicals does a great job cleaning your workpiece further than your tack cloth could ever dream of (however these liquids don’t do much for large particulates and dust, which is why we always tack cloth before this final cleaning.)
Step 2: Primer
Primer is a recognizable word to almost anyone who has heard of paint. A primer is similar to paint in coverage but is very different in composition. Primers have a higher concentration of pigments and solid matter in relation to their liquid counterparts. Thus, when your base liquid (water for latex & acrylic primers, alcohol for enamel-based primers) evaporates out of the mix you are left with a thicker and much more opaque layer of sediment on your workpiece. The ratio of liquid matter to physical matter varies in the different types of primer, so you will use different primers depending on your project and material.
If you are prepping a 3D printed model for your Dungeons and Dragons campaign, you may find pinholes and scratches from rough sanding or irregularities from the 3D printer. In this case, you will choose filler primer or sandable primer- 2 types that allow a thick coat of sediment to be left on the workpiece to “fill” these small imperfections. Sand down that primer until the filled spots blend in and you’re all set with a smooth piece.
However, if you’re priming a food truck before paint you will A) want a smoother and thinner primer to reduce unnecessary sanding on an already-smooth surface and B) will need an aluminum-specific self-etching primer so this base layer chemically bonds with your car door’s metal and doesn’t flake off after a month like if you used a different kind of primer
These are just 2 examples that come to mind when reflecting on the importance of choosing an appropriate primer. When in doubt ask your local hardware store or paint store clerk for guidance- some of us get paid to really nerd out about this kind of riveting stuff!
You will typically want to have enough primer for 2-3 full coats to ensure proper coverage. This isn’t *quite* as important as multiple paint coats, but it is good practice. It will also reduce runs and drips if you try and blast 1 heavy coat all at once.
I don’t care if you’re brushing, rolling, spraying, or finger painting. Remember that the rule of thumb is 3 coats of paint per color for complete coverage, and this goes for primer too.
Step 3: More prep
Alright, our workpiece is primed and it’s finally time to paint, right? Wrong. First go have a smoke and a beer while the primer dries, as we can’t do anything else until it's completely dry. Once dry, we will scuff up that workpiece so the paint grabs.
Now that everything is dry go ahead and put your respirator and gloves back on, and grab a piece of Scotch Brite. You want to scuff up every visible surface of the primer in order to give this flat layer a “tooth” for your paint to grab onto. The more scuffed up the better, but if you’re getting impatient then hitting everything with at least a once-over of Scotch Brite is better than nothing.
Remember that tack cloth you had before and are probably sick of using? It’s time to break that puppy back out and wipe down all of the dust created by Scotch Brite-ing the whole workpiece. Once you feel confident in how little dust remains on your workpiece, it is time to paint.
Step 4: Painting! Finally
Before even starting this section I will reiterate that the rule of thumb is to do 3 coats of paint. It is so much easier than you would expect to miss a section with paint twice in a row, or to get a run in your paint if you try to blast through this step in 1 or 2 heavier coats. You will also want to spray the ENTIRE PROJECT, even if only 1 section will stay that base color after taping off areas and hand painting some sections. Painting the entire thing is easy enough and will prevent uneven textures or glossiness differences in the finish when all is said and done. Prepare to paint by having enough paint of EVERY COLOR you need to cover the entire workpiece.
Coat 1: This is referred to as the “tack coat” or the “feather coat”. You want to spray as lightly as possible and pretty far away from your workpiece. This sounds counterintuitive but, trust me. As the alcohol in your enamel-based paints evaporates off it will create that signature sticky surface that spray paint is known for, which will help you tremendously in preventing drips and runs in the next 2 coats. As stated before, paint the entire thing even if this base coat only accounts for one section of the finished piece. This thin layer should dry (or “flash off”) within 10 minutes, so by the time you’ve made the whole pass, it’s almost time for coat number 2.
Coat 2: Time for the first real paint coat. Pick a direction, horizontal or vertical, and stick with it the entire coat. Spray 1 continuous line- none of this stopping and starting in the middle nonsense. You should look like you’re doing Capoeira by using your entire body to stretch far enough to carry your paint line from end to end. For the next line- aim for the bottom of your spray output’s footprint to hit the center of the previous line. Think of it as overlapping rather than stacking paint lines. This will prevent the lighter & less opaque areas on the edge of your spray footprint from making streaks (or “tiger striping” as we call it in the biz.) It is very hard to blend in tiger stripes retroactively, so err on the side of more overlap if this frightens you. Cover the entire project in this first heavy coat, then go grab another smoke and another beer for 20-25 minutes while it flashes off. You want it to be a dry and tacky coat to the point that it will absorb fingerprints when you come back to it. However, spray paint specifically needs to be recoated within 1 hour to prevent weird chemical reactions from taking place. Not a big deal, but something to keep in mind when you’re slamming drinks in between coats.
Coat 3: This is the lasting impression of your paint job so get ready for a mentality of striving for flawless perfection the entire time you’re spraying. If you went horizontal on coat 2, you will switch it up and go vertical on coat 3 (or vice versa). Stick with the same overlapping pattern, this time with more overlap. Your 3rd coat should be the heaviest spray of all. People have different methods of how thick to go based on experience and feel, but my adrenaline junkie brain likes to get my paint one dirty look away from dripping and running all over the workpiece. I like it thick. Spray every square inch, making sure you hit all of the interior angles and any spot that could possibly be visible.
Step 5: You did it champ!
Clean up your supplies and crack one last cold one for a job well done. Don’t even think of poking that wet paint… I know how tempting and fun it is but you’ll be sanding all of this hard work off and redoing everything tomorrow if you touch it.
Most enamel paints have a 24-hour cure time, depending on the ratio of paint to alcohol in your mixture. So stay busy for a full day and come back to check out your beautiful piece, and pray to your respective lord that a bunch of dust didn’t fall on the workpiece overnight, or worse yet that a bug landed on it and got stuck.
Happy painting.
-Charlie
