The Process That I Use

My process for applying latex paint starts with brushing on primer, sanding it smooth, spraying on the color coats, sanding that smooth, and polishing the finish.

Covering

I prefer Stewart Systems EkoBond adhesive instead of the MEK based products.  The stuff does not stink and is super easy to use.  You simply paint it on, let it dry a little, lay the fabric in place, and press the fabric into the glue.  If misalign the fabric you can pick it back up and reposition it. When you are satisfied you use an iron the lock it in place.  There are a series of great how-to videos on YouTube that show the entire process.  Even though I don’t use PolyFiber, their manual is an invaluable resource for applying covering and stitching. You will need some rib stitching cord and a long needle to stitch the fabric where required.  And a bunch of cheap 2 inch chip brushes for applying the glue.

Primer

The primer serves two main functions. First, it provides the mechanical bond to the fabric. Latex, and some other finishes, do not chemically bond to the polyester fibers and therefore must encapsulate the fibers to create a bond. The good news is that latex does this extremely well. The second function for the primer is to fill the fabric weave to provide a smooth surface for the color coats. I use Gliddon Gripper Latex Primer in gray, thinned about 20% with water, or to a 24 second viscosity (see viscosity page).  I apply several thin coats with a foam brush, first brushing east-west, and the next coat brushing north-south. The primer dies quickly, especially if you can get the part into the sunlight.  I sand lightly with either 220 0r 320 grit dry paper.  This helps smooth the brush strokes and removes high spots left from brushing.  Be careful not to sand through to the fabric however. The second coat of primer is brushed on perpendicular to the first.  I continue this alternating pattern for a total of 6 coats, sanding after each coat.  This fills the weave quickly and economically. After the primer coats have been applied and sanded you should have a smooth, uniform surface, ready for the color coats.

primer

If you are painting metal or fiberglass surfaces you will not need as many coats of primer. These surfaces can be sanded to provide some "tooth" for the latex to grip. There are also any number of specialty products available to prepare alumimum for paint.

Color Coats

I've tried a few different brands of latex paint and they all seem to work quite well, but Sherwin Williams is my favorite for a glossy finish. I use the "ALL SURFACE ENAMEL, Arcylic Latex High Gloss". It's available off the shelf in a handful of standard colors, or they can mix to any color you desire.

I used Behr Premium Plus High Gloss Latex for my Pietenpol Air Camper and got a nice finish also. One of the advantages of latex paint is the array of colors available.  Some stores can even computer match color samples that you may have so that you can get an exact match to other parts of your project. I use water (I used to use windshield washer fluid but saw no difference) to thin the paint about 20% or 24 second viscosity (see viscosity page). I have tried floetrol, but it didn't seem to do anything. You will probably discover the right mix for your own paint, your own spray equipment, and your own painting style. I use the cheap paper and mesh paint filter cones when I pour the paint into the gun. This is important to keep debris our of the gun. Unless you are fortunate enough to have a dedicated spray booth you will have to set up a temporary one.  I like to use inexpensive drop cloths for the walls and Harbor Freight canvas drop cloths for the floor.  We will be wet sanding later and plastic on the floor would be very slippery.

Lowes HVLP

I have tried a Craftsmen gun, and a cheap spray gun that came with a diaphragm compressor, and a cheap Harbor Freight gun, but none would spray latex unless it was drastically thinned.  I have had great success with the Harbor Freight Touch Up gun which costs $12.99 on sale.  This gun is great for small parts, but a wing or fuselage would be a challenge.  While patrolling the isles at Lowes I spied this $50 gun which is called a Latex Spray Gun.  I reasoned from the name that it might be a good choice for spraying latex paint and it sure was.  I used this gun for most of the Pietenpol and Tornado painting until I got a little lazy cleaning it and it developed a clog.  No amount of disassembly and cleaning has been able to fix it. My favorite spray gun is from Harbor Freight and I picked it up with an online coupon for $11.99.  It's gravity feed, has great control for air, paint, and spray pattern, and is called an HVLP gun.  I use 35 to 40 PSI for all the guns which seems to work well. You of course will need an air supply, the compressor not the band.  I have a big monster compressor which is a luxury.  Almost any compressor will work.

As we did with the primer, alternate the spray pattern 90 degrees each successive coat. As soon as you are done painting dump the remaining paint back into the specially designed cup, and drop the gun into water.  Fill the reservoir with clean water and spray the clean water through.  Repeat this with clean water again.  Then disassemble the gun, wash all parts, and dry with compressed air.  It sounds like a pain, but it really only takes about 3 minutes, and you will be able to use the gun for a long time.

If I had a better paint booth I could probably avoid some of the dust specks that seem to always appear, but I deal with them by sanding. Sanding removes the dust specks and other junk that finds its way into the paint surface, and it further smoothes the surface. I use 600 grit wet sandpaper folded over, with plenty of water.  Sand enough to remove the unwanted stuff, but be careful not to remove too much paint. It's easy to sand off the paint from the pinked edges of the tape and the high spots where the rib stitching is.  This is not a problem for the first color coat, but you will want to be careful to stay away from these areas when sanding successive coats. I spray 3 or 4 coats, sanding after each one.  After the final coat I let it dry for a couple of days and then its time to wet sand and polish.

wet

For wet sanding use a sponge to distribute the pressure from your hand.  Cut sandpaper to fit the sponge and soak the paper and sponge in water.  Wrap the paper around the sponge and start sanding, using the squirt bottle to keep the surface wet.  This prevents the paper from loading up.  Frequently wash the paper in a water bucket to remove debris. Start with 1000 grit using very light pressure.  The paper will almost grab the surface and you just need to move is back and forth.  Be very careful around edges and high spots, in fact, just stay away from them.  Actually, it's a good idea to just tape over the edges of the pinked tapes with masking tape to prevent you from sanding the paint off of them. You will remove the dust and "orange peel" irregularities with the 1000 grit, and use the 1200, 1500, and 2000 grit to remove the sanding scratches created by the 1000 grit.  If you have done a good job applying the paint, then you might be able to skip the 1000 and 1200 grit and start with the 1500 grit. Wipe the part down after each sanding grit to remove any residue.

dull

We’re almost done.  All that’s left is the polishing.  Buffing the paint to a nice shine is actually quite easy. I have been using a $35 Harbor Freight variable speed buffer for years. I have tried both wool and foam bonnets and prefer the foam. I use 3M Perfect-it polishing compound, available at NAPA and other auto part stores. After the paint has been sanded with 2000 grit wet paper, use a spray bottle of water and paper towels to clean sanding residue from the paint surface. Apply a glob of the polish to the paint surface and spread it around with the bonnet without turning the buffer on. On vertical surfaces apply the compound directly to the bonnet and smear it over the paint surface. Set the buffer to its slowest speed and start buffing. Use a light to medium pressure and let the polish work. Keep the buffer moving over a 2’ by 2’ area. Use care around edges and protrusions. If you do polish through the paint don’t panic. It can easily be touched up with an artist brush (I know!). The finish will shine up very quickly and you can then move on to the next area. After polishing 3 or 4 areas it will be time to clean the foam bonnet. Remove the bonnet (Velcro) and immerse in a bucket of water. Use your hands to rub the paint out of the foam. Put the bonnet back on the buffer, hold it horizontally in the bucket, and run the buffer at high speed for about 10 seconds to fling out the water. Now you are ready to polish some more. If you notice that you are getting a build up of dried polish/paint on the paint surface then it’s time to clean the pad again.

Protect the finish with a good coat of car wax.  I wax a couple times each year and find the wax makes a good cleaner also.  I clean grease, oil, and bugs first with household cleaner.  A careful job of painting can limit the dust and irregularities in the paint, but I think that the results of sanding and polishing are worth the effort.

FinishedRudder

Roller Application

I have tried more experimenting with foam roller application of paint.

Above is a test panel that was primed with 4 coats of Gliddon Gripper using a foam brush and sanded with 220 grit. I then tried brushing thinned Sherwin Williams blue but it was way too streaky, so I switched to a foam roller for several more coats. I should have put on a few more coats of blue as you can still see the brush marks.

I sanded with 1000, 1200, 1500, and 2000 grit wet and polished. I came out smooth with a good shine, but did not have the depth of the sprayed finish.

I continued to experiment with the roller application, this time on the aluminum pieces for the front of my Micro Mong. I brushed on 2 coats of Rustoleum latex primer for aluminum and sanded with 220 grit. Then I rolled on 4 coats of Sherwin Williams, thinned as I would for spraying. The result was moderate orange peel and some dust.

After wet sanding with 1200, 1500, and 2000, and polishing I was surprized at the finish.

Above is the painted piece on the airplane. I seems that polishing technique is the key to getting depth in the finish.

After some more work on rolling technique I've created the following video. I believe that a great looking finish can be achieved by rolling on latex paint, followed by sanding and polishing. Have a look:

Rolling on Latex Paint

Videos

Here are a few videos that show the sanding and polishing process.

Polish or Not Polish

Sanding the Wing

Polishing the Wing