In my assembly, I used glue and 18 gauge brads, then pre-drilled and countersunk screws to pull it tight. (That's the carpenter coming out in me). Glue and clamps only will save some filler work.
Shinobiwan makes some good points I will bring up before getting to the spraying. As the title states, no roller finishing here. No spray cans either. Need to get a gun if you want to get serious into this hobby. To get enough air (i.e. big compressor) and a good gun is some $$. For one-timers, here is a good time to consider just paying a finishing shop to do your box.
I have a DeVilbiss PRI Gravity HVLP Primer Gun
- 1.4 mm Fluid Tip. It is a nice gun, but an air hog. It needs about 16 cfm to run continuously. A 1.8 mm tip would be better for primer, but I use the 1.4 because it's a nice size for the lacquer.
HVLP - High Volume Low Pressure. Don't get a conventional, siphon feed, high pressure gun. You'll get more spray in the air - overspray, blowback . You get a higher TE with HVLP - transfer efficiency. More of your expensive finish stays on your project and not on the floor.
Other nice guns:
- Asturo Eco.
Buy a good one it you plan on doing this often with good results.
Here is a site for suggestions and price ranges
Atomization is the process in your gun that turns liquid into mist. It's the air that breaks up the paint/finish. It's all about the gun. A Harbor Freight, Depot Husky gun (paint spitters, cough, cough) will do it, but not nearly as well as a good gun. More air will do it better, but there are low-air/low cfm options
that will do a good job.Air is next.
You don't need a compressor with the rated CFM higher than your gun will draw. If your compressor only puts out 5, but the gun draws 10 = just means more waiting-time for the compressor to catch up once you empty the tank. You still can spray, but a bigger tank and more CFM is better. I have an 220 volt Energair, I think it's a 25 or 30 gallon tank. I never wait for air, and it's not running all the time.
Also, make sure you have an air/water separator. Most finishes don't like moisture in the compressed air - good cheap investment. (At the shop we have a rotary screw compressor and a refrigerated air line dryer with a secondary filter - almost hospital clean air!!) Not needed though for this discussion.
I run full pressure in the hose to the gun, I added a regulator at the gun to control the pressure there. Not only for control, but you get too much of
a drop if you only run 25 -30 psi in the hose. (See above gun pic)OK, Finally to the primer!!!
For this I will be using a two-part, polyurethane primer. It is a high-solids primer, 65%. It will build nice, dry to the touch in minutes, sand to a powder in just a couple hours. My favorite is an Italian one - Vernici Egidio Milesi.
This box is about 5 cubic feet. I will need about 12 oz of combined finish to hit it. Use the graduated plastic mixing containers. Easiest way to measure. (Cheap if you buy bulk, not sure the deli potato salad containers are solvent resistant )
This 1st Batch = 7 oz poly, 3 ½ oz. hardner, +/- 2 oz. thinner.
When I say thinner, not Lowes mineral spirits! The thinner supplied with your poly (of course purchased separately). This Milesi one is some what picky, the thinner runs about $20 gal.
Tack the sub, use the (very little bit of) thinner and a new clean rag to remove dust. As for spraying technique, easier to show than describe. Just trigger in the air off the sub, and release once past the edge. Car guys will hold on and spray almost non-stop. Don't be triggering on/off too much.
After all nice and black, I hit it again with the wood block, and 220 grit this time. This is your last shot for major fixes it you missed anything. You are looking for the whole surface to get scuffed and powder evenly. Here is the top with real good prep. Front baffle looked good too. Just a few high spots.
Here is a side that had somewhat poor prep for a high gloss.
Um, well, you see, yeah... I rushed through the bondo work / sanding on purpose for photo demonstration purposes yeah, that's it! I was sloppy for your benefit!!
(OK, caught me. Just rushed )
Ended up doing some more sanding and 3M Acyl-blue.
Since a good portion of that 1st coat got sanded, I gave it two more coats of primer, 90 minutes apart.
Here it is, waiting for the next step. I took the shot right off the gun, so still drying. Plus the flash added something funky. But it looks nice - flat, smooth consistent black.