How to Achieve a Flawless Painted Finish
Each month when I preview our guest writer’s article prior to publication it always stirs up thoughts and experiences I’ve had over the years. This month Bill Perry writes about applying painted finishes.
I know I’ve mentioned this in previous letters I’ve written to you but one thing always stands out in my mind when applying a painted or solid color coating to a wood surface. Specifically the type of wood you are painting on and paint shrinkage.
If you remember some months back I told you one of my piano refinishing stories where I was asked to turn an old mahogany wood piano into a black ebony piano. Basically, a black ebony finish is a painted finish. To abbreviate the story, I failed to fill the grain and the grain reappeared. Lesson learned: paint shrinks in the curing process. Open grain woods need to be filled prior to painting to counter the effects of paint and coating shrinkage.
To change gears for a moment and still thinking about painted surfaces, one of the most frequently asked questions is about spraying latex or emulsion type paints with HVLP technology. This is not the easiest question to answer but let me try to put this in perspective for you.
- HVLP technology is generally considered a fine finishing tool to apply light to medium viscosity paints and coatings. This is where it will provide the best overall results.
- Can you spray latex or emulsion paint with HVLP? Yes. But here is what you need to know:
- Latex paints differ in their formulation, composition and viscosity.
- In the manufacturing process, many latex paints have coarse ground resins and pigments, unlike other coatings where the resins and pigments are finely ground.
- The reason is that latex paint is generally made to be brushed, rolled or applied with airless spray technology rather than an air atomizing technology such as HVLP.
- HVLP sprayers vary widely in the available nozzle pressure. Smaller, lower powered, less expensive HVLP turbine units do not have the pressure necessary to apply a generally acceptable smooth finish.
- While you might get the paint to come out of the spray gun with a low powered HVLP system, application speed will be slow and the finished surface either wavy (orange peel) or coarse.
- Thinning the paint is necessary to improve the ability of the equipment to atomize the paint better and the addition of a latex conditioner (Floetrol) will assist in helping the finish flow and level better.
- How much you need to thin the product will depend on the size of the turbine unit, available pressure, and the quality of the paint selected. This will vary anywhere from 10% to 50%.
- The downside of thinning latex paint is loss of sheen. A gloss sheen can become virtually a flat sheen with excessive thinning.
- Slower drying and multiple applications are also issues.
- On the brighter side, newer more powerful turbines (4 and 5 stage units) that put out much higher atomizing pressure allow less thinning (10% or less) and excellent results.
Before spraying latex paint with an HVLP sprayer, determine what you are trying to accomplish.
- If you are spraying a fence, outdoor furniture, or similar applications then you might not be looking for a “piano” finish and the end result with latex paint will be more than acceptable.
- On the other hand, if you are spraying cabinets or furniture where you desire a painted finish, you might want to consider a product specifically designed for spray finishing. (Waterbase or solvent base).
- If you need to spray latex paint to match a particular color and this is the only material available I would like to suggest that you look for a high quality latex enamel, use HVLP with the highest available air pressure, and understand the relationship between available air pressure and product viscosity.
While one would think that applying paint to a surface is easy, like any other skill, knowledge is key to the easiest path and best results.
This month’s article by Bill Perry has some wonderful thoughts and ideas for you.
Sr. Vice President and COO
Apollo Sprayers International, Inc.
It is not every day that a new product literally takes the market by a storm, but that's been the case ever since Apollo Sprayers launched Apollo Model 7500, the AtomiZer. It has won several major awards and a legion of fans across the world. It is the ultimate HVLP Spray Gun that has revolutionized spray finishing. This unique gun delivers enhanced TrueHVLP performance and flawless results with any make turbine or air compressor, 3HP/20 gallon (75 liter) tank or larger. The AtomiZer's excellent ergonomic design and comfort of usage won it Popular Woodworking's “Best New HVLP Tool” Award and the coveted AWFS Sequoia award.
These exclusive features make it a pleasure to use, and make a better finisher out of anyone who uses it:
- Precision fan control through the Xpansive™ Fan Control Ring
- New technology for atomizing particles – MicroTech™ Atomization
- A major advance in balance and lightweight design
- Durability and reliability ensured with internal parts expertly engineered from marine-grade stainless steel and NO "O" rings
- Color-coded air caps make changing a complete range of nozzle and needle sizes quick and easy
Finishing Feature Article by William Perry: How to Prep for a Flawless Painted Finish
While we may think that applying a film finish such as lacquer or polyurethane over natural wood can be a challenge, here’s a much tougher one: achieving a flawless painted finish. Blemishes in a clear film finish are disguised by the color and grain pattern of the wood. There’s no such hiding place with paint. Light playing across a painted surface only draws attention to any surface defects – and any pattern of wood grain showing through paint now becomes a defect instead of a feature.
As with most things, there’s good news and bad news about this.
The good news: you can achieve a finish so flawless that it looks as if it belongs in an automobile showroom READ MORE
Finishing Tip by Bob Flexner: A Basic Understanding of Solvents
The following is a basic understanding of the common solvents available in paint stores and home centers.
Mineral spirits (paint thinner) and naphtha dilute and clean up oils and varnishes, including oil-based polyurethane varnish. Neither of these solvents damage any fully dried finish, so you can safely use them for cleaning—that is, removing grease or wax.
Denatured alcohol thins and cleans up shellac. This solvent will damage a dried shellac finish almost instantly and lacquer and water-based finish fairly quickly, so be very careful if you use alcohol for cleaning.
Lacquer thinner and acetone thin and clean up all solvent-based lacquer products. These solvents can damage all wood finishes, so don’t use them for cleaning.
Super lacquer retarder containing butyl cellosolve, also called ethylene glycol mono-butyl ether or “EB,” evaporates very slowly, so it can be used to slow the drying of lacquers, shellac and water-based finishes. But use very little (less than 5%) or the finish may take days to fully dry.
Toluene (tolulol) and xylene (xylol) have very little use in wood finishing, though they can be very effective for cleaning grease from metal.
Finishing Tip by Bob Flexner: Removing Wax Smear
Paste wax is easy enough to apply. Simply wipe it on the surface. The problem comes in removing the excess wax, because if you don’t remove all the excess, it leaves a smear rather than a shine.
The trick is to use a clean cloth or lambs-wool pad for the removal—with the emphasis on “clean.” If you continue to wipe off the excess with a cloth or pad that has become loaded with wax, you will just be moving the wax around the surface rather than transferring it to the cloth or pad.
So, whenever the cloth or pad become loaded with wax, refold the cloth to a clean area or replace the cloth or pad with a clean one.
To make removal easier, apply the wax thin to begin with. The easy way to do this is to wrap the paste wax in a cloth so that all that is being applied is the wax that seeps through the cloth.