Bend the Rules and Be Brave!
I have always been an obedient person who knows the rules and tries hard to follow them. This aspect of my personality rolled over into my finishing. For years I tried to follow the advice on the coating can, the instructions in finishing tool manuals, and advice from various experts. Pretty soon I had my own set of rules for finishing and I got excellent results. I was reluctant to try new things. Then, bam! A light went on in my obstinate head. I had always sanded to 400 grit before spraying the first coat of water base, but if Bob Flexner and Glen Huey suggest 180 to 220 grit, why not try it? They believe that the surface should be a bit rougher and to my astonishment it worked out fine.
When a coating manufacturer provides instructions on viscosity, I discovered that this too leaves room for adjustment. There are many different finishing technologies, so a coating manufacturer can only address one or two. I’ve learned that most coatings have comfortable variables as far as adjusting viscosity. Too high a viscosity won’t work, but there are wide variables when it comes to thinning provided that you control the application. This led me to include the word “guideline” when writing our instruction manuals and providing information on suggested viscosities for various coatings.
Then I discovered that experimenting with different nozzle and needle sizes beyond the suggestions produced interesting and often better results. The same being true for trying alternative air caps other than the one recommended for the corresponding nozzle and needle size. I found that using a smaller air cap size gave me slightly higher air pressure and a finer atomization. I also noticed that the fan size was a bit smaller. When I used a larger size air cap with a smaller nozzle and needle I got a larger fan pattern and more atomizing air making it easier to atomize a coating that flowed well through the smaller nozzle size but was on the higher viscosity scale for the particular size nozzle.
Speaking about being brave, recently in Beijing I was blown away by the demo I saw at the auto after-market industry trade show. Our very brave representative, Dong YiPeng, brought his brand new navy blue Mercedes into our booth. Using a large screw driver he made a deep 10 inch scratch on the hood. The onlookers were stunned. So was I! Dong filled the gouge, sanded and then sprayed matching paint. The surface was perfect. I saw him do this demo five more times. Each time I was terrified and each time Dong’s skill and the Apollo 835’s perfection came through to the delight and applause of the audience. I am not suggesting you try this on your car, but it can be very rewarding to be brave. Dong certainly got a great response to his demo.
If you have an interesting example of bending the rules, be sure to let me know at [email protected]. You may be appearing in a future newsletter. Meanwhile, I wish you a fine finish.
Bill Boxer
Sr. Vice President and COO
Apollo Sprayers International, Inc.
Selecting Nozzles, Needles and Air Caps
Some finishers are devoted to just one coating and they know exactly which needle, nozzle and air cap works best for them. However, you might want to experiment with a different air cap.
If you use a variety of coatings, the chart below is a general guideline of recommended nozzle, needle and air cap size to use with various coatings and viscosities for the Apollo 7500 series spray guns. Different coatings as well as different brands may have properties that will work better with an alternative size nozzle and needle or alternative air cap. Most often these standard recommendations will work perfectly. At other times you might want to experiment with a different combination. Nozzle and needle sizes always need to be paired.
When you experiment, generally, a smaller nozzle size would be used for a thin or low viscosity product. This helps control the flow of fluid and ensures that all of the fluid is properly atomized. As viscosity increases, or higher fluid flow is desired, a larger nozzle/needle pair is suggested.
|
FLUID NOZZLES, NEEDLE ASSEMBLIES, AIR CAPS & VISCOSITY for Apollo 7500 Series. Check Manuals for Other Series.
|
|||
|
NOZZLE/NEEDLE SIZE
|
APPLICATION |
VISCOSITY ZAHN #2 |
AIR CAP |
|
0.8MM (.031) |
Inks, Dyes, Stains, extremely thin viscosity fluids, Water based finishes |
16 seconds |
A |
|
1.0MM (.039) |
All purpose, thin lacquers, thin enamels, Water based finishes, Automotive, Marine, Airplane finish |
16—18 seconds |
B |
|
1.3MM (.051)
|
Same as 1.0mm above except slightly higher viscosity. |
17-20 seconds |
B |
|
1.5MM (.059) |
Catalyzed lacquers, Conversion Varnish, Primers, Automotive, Marine, Airplane finishes, Varnish, High Viscosity Industrial Coatings, Urethanes, Enamels. |
18—24 seconds |
B |
|
1.8MM (.070)
|
Same as 1.5mm above except slightly higher viscosity. |
20 – 22 seconds |
C |
|
2.0MM (.079) |
Thinned latex paint, Multi-spec, Heavy Primers, Butyrate, nitrate dope, High Viscosity Industrial Coatings |
24—35 seconds |
C |
|
2.5MM (.098) |
Thinned latex paint, Multi-spec, Solvent adhesives, Wax based strippers |
35+ seconds |
D |
Apollo Sprayers offers two different air cap sets. The standard air cap (picture) for fine atomization and distribution of coating (Available in sizes A, B, C and D) and HS (High Solids) air cap (designed to increase nozzle pressure for hard to atomize and higher solids products. The HS series is available in sizes B, C and D.
Finishing Article – The Pros and Cons of Waterborne Finishes by Charles Neil
This month Charles Neil, with over 30 years of unique woodworking expertise, joins our writing team. He shares his experience and knowledge while demonstrating his goal of keeping it simple. Charles Neil’s DVDs, newsletters and YouTube site educate thousands of woodworkers.
Having picked up my first spray gun at 13-years of age and now being 58, I have sprayed about everything. My beginning was in automotive finishing and it remained my career for the next twenty years, then I switched to woodworking and finishing.
As with most finishers, I began with the old nitrocellulose lacquers and while they were very friendly to use, they were less than a long-term hard use finish. Then came the pre-catalyzed and post-catalyzed lacquers, a big improvement and they remained relatively user friendly. READ MORE
Finishing Tip from Bob Flexner: Shellac Flakes Offer Color Variety
In addition to shellac in dissolved form, which you can find at most paint stores and home centers, shellac is also available in flake form for you to dissolve yourself in denatured alcohol.
One of the advantages of dissolving your own shellac is the variety of colors available. For example, in the accompanying photo, from top left to bottom right, the colors are super blonde, orange, button, garnet, extra dark and seedlac, which is unrefined shellac.
Keep in mind that the flakes shown are much thicker than the shellac will be when used as a finish. So the colors you get on the wood aren’t as dark.
Finishing Tip from Bob Flexner: Stirring Stain
Don’t be fooled by the color of a stain just after you remove the lid, especially with water-based stains. With these stains the combination of binder and solvent may be off-white, which is not at all what you are expecting.
The pigment will have settled entirely to the bottom of the can, and it may have hardened enough so that shaking the can doesn’t bring it all into suspension. It’s always best to stir the stain with a stirring stick.
When you remove all the pigment off the bottom of the can and into suspension, the color of the liquid should be what you are expecting.
Keep in mind, however, that pigment is heavier than the liquid and will begin settling soon after stirring. If you are staining a large project, or if some time goes by between staining separate objects or sections of an object, you should stir the stain again before using it, or you may get a lighter coloring.
The two images below help illustrate. The first image is of unstirred stain and the second is of stirred stain. Notice that you can see the color after you stir the stain.
