Tech Questions - Applying the Topcoats
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- How long should I wait after spraying Poly-Spray before I start spraying on color coats?
- What are my choices for color coats?
- Can I use Poly-Tone on metal parts?
- How can I match Poly-Tone on fabric and Aerothane on metal?
- What kind of primer should I use on metal parts?
- My friend used a high quality automotive polyurethane on his airplane. It looks good. Why not use that?
- What about using butyrate dope as a color coat?
- What about lacquers or other enamels?
- Do you think I can spray the color coats myself or should I hire a professional?
- What kind of spray equipment is best to use?
- I have heard people say you should spray a coat of white over the silver before spraying on the final color. Why is that?
- A friend of mine said that he found the colors to be different when he ordered additional gallons. Can that be a problem?
- Should I shake the paint prior to applying it?
- How about turning the cans upside down during storage?
- What about using a clear coat over the final color?
- Is it important to clean the surface just prior to spraying on the color coats?
- How do I thin Poly-Tone?
- What about straining the paint through a paint strainer?
- How many coats of Poly-Tone should I apply?
- Do I have to sand between coats?
- What about Aerothane and Ranthane? How many coats are required?
- How do I mix Aerothane and Ranthane? I notice it has two parts.
- Do I have any time restrictions on using Aerothane and Ranthane paints after it is catalyzed?
- The can of catalyst I received appears milky. Should I use it?
- How do I thin Aerothane and Ranthane?
- My Poly-Tone has been sitting for over 3 years. Is it still OK to use?
- What is the shelf life of Aerothane and Ranthane paints?
- How long should I allow the topcoat to dry before I mask off an area for trim colors?
- What kind of masking tape should I use to mask off trim colors?
- What kind of paper should be used to protect painted areas while I am spraying trim colors?
How long should I wait after spraying Poly-Spray before I start spraying on color coats?
A good rule of thumb is to wait at least 4 days between the last coat of Poly-Spray and the first coat of color. This allows all of the solvents to completely evaporate. This is most important when using Aerothane.
What are my choices for color coats?
You have three choices. Poly-Tone, Aero-Thane, or Randolph Ranthane. Poly-Tone is the same basic chemical as Poly-Spray except it contains color pigment. It is easy to spray, easy to repair, and provides a long-lasting satin finish. Aero-Thane and Ranthane are polyurethane paints that provide a high luster and high durability. They are somewhat more difficult to spray. Aero-Thane and Ranthane may be applied to both fabric and metal making them good choices for matching paints on two different types of surfaces. One word of caution: If you are spraying Aero-Thane or Ranthane, you must use a fresh-air breathing source. Like all polyurethane paints, you must not breathe the fumes or mist.
Can I use Poly-Tone on metal parts?
You can use Poly-Tone on metal parts if you apply it according to the manual. Basically, that means prime the part using EP-420 epoxy primer. While the primer is still drying spray one coat of Poly-Tone directly onto the tacky primer. Let this dry for 8 hours then spray another coat of Poly-Tone.
How can I match Poly-Tone on fabric and Aerothane or Ranthane on metal?
This is a good way to spray color on your airplane. You have the best of both worlds. You can match the two by adding a flattener to the Aerothane or Ranthane. Each can of flattener has instructions on how many fluid ounces to add to Aerothane or Ranthane. This, along with buffing the Poly-Tone on the fabric will match colors very well.
What kind of primer should I use on metal parts?
Use only an epoxy primer. Two colors are available. Green and white. If you are using a light color as the final topcoat you should use white primer. Otherwise, the green color may be difficult to hide.
My friend used a high quality automotive polyurethane on his airplane. It looks good. Why not use that?
This is a common question. Automotive paints are great for metal but not for fabric. They are not flexible thus cracking will result in time if used on fabric. Remember that your fabric will move and flex. The topcoat must be able to do the same. DO NOT use an automotive enamel on fabric unless you want to deal with cracking problems at a later date.
What about using butyrate dope as a color coat?
Absolutely not! Butyrate dope is not compatible with Poly-Fiber products.
What about lacquers or other enamels?
No. You will have problems. Only use Poly-Tone, Aerothane or Ranthane color coats.
Do you think I can spray the color coats myself or should I hire a professional?
Our recommendation is that you do it yourself. After spraying the Poly-Spray you will have enough practice and experience to do a good job with the color coats. Again, practice on something other than your airplane when you first start spraying color. You will also want to construct a small spray booth out of clear plastic to keep dirt and bugs out of the final coats.
What kind of spray equipment is best to use?
You can use either a high pressure gun or a HVLP system. Whatever you have been using for your Poly-Spray coats you can use for color. If you are using Aerothane you will probably need a different nozzle for the spray gun.
I have heard people say you should spray a coat of white over the silver before spraying on the final color. Why is that?
Spraying a coat of white over the silver will definitely provide better coverage if your final color will be red or yellow. It will also cause the final color to be richer.
A friend of mine said that he found the colors to be different when he ordered additional gallons. Can that be a problem?
It is a potential problem. Care is taken to ensure proper color match between batches of colors. To be on the safe side, we recommend that you purchase the total amount of color needed then mix all of the gallons together in a 5-gallon pail. You can then repour them back into the 1-gallon cans. That will ensure that there are no minor differences in color. Not properly shaking or mixing the paint can also present a matching problem.
Should I shake the paint prior to applying it?
Absolutely. Take the topcoat paint to a local store and have them shake each can for 5 minutes. This way you will be sure the color pigment is mixed completely. Use the paint within 1 week after shaking.
How about turning the cans upside down during storage?
That is an excellent way to keep pigments in suspension. Do this about every 30 days or so prior to use.
What about using a clear coat over the final color?
We do not recommend using clear coats. They work fine on automobiles but they can promote the growth of fungus on fabric.
Is it important to clean the surface just prior to spraying on the color coats?
Definitely. You will want to clean the surface using C-2210 Paint Cleaning solvent with a clean rag. Then, just prior to spraying, remove any dust using a tack rag.
How do I thin Poly-Tone?
Poly-Tone is thinned using our regular thinners, R65-75 or R8500. It should be thinned at the ratio of 1 part thinner to 4 parts Poly-Tone. Use R8500 when the temperature is above 85 degrees F.
What about straining the paint through a paint strainer?
Use a 60 x 48 mesh paint strainer to pour the paint through into the spray cup.
How many coats of Poly-Tone should I apply?
Normally, three cross-coats of Poly-Tone are sufficient. You should do no more than 2 cross-coats in a one-day period. Spray one coat in the morning, let it dry until mid-afternoon, and then spray another coat.
Do I have to sand between coats?
You should only have to sand if you have a run, a sag, or some other problem.
What about Aerothane and Ranthane? How many coats are required?
For Aero-Thane we recommend a light color coat, a medium coat, and a final wet coat. For Ranthane we recommend a tack coat, a moderate coat, and a third wet coat.
How do I mix Aerothane and Ranthane? I notice it has two parts.
You must catalyze both Aero-Thane and Ranthane, and they use different catalysts. Aero-Thane is mixed 3:1 with its catalyst U-865. Ranthane is mixed 2:1 with its catalyst AU-CAT-2X1. For both catalyzed paints, let sit for 20 minutes induction time before thinning with their respective thinners.
Do I have any time restrictions on using Aerothane and Ranthane paints after they are catalyzed?
Yes, you should use the catalyzed paint within 5-6 hours; the sooner applied after the induction period, the better the durability. Otherwise, it will begin to crosslink and thicken. Mix only the amount of paint you will be using at one time. If you happen to mix too much you can place the paint in a freezer (away from any food) for a short period of time. This slows the chemical reaction. You can then take it out, let it warm up and spray it. This will work for a couple of days.
The can of catalyst I received appears milky. Should I use it?
No. Do not use any catalyst that appears milky or stringy. Also, if the can is swollen do not use it. Order another can. The catalyst should appear thin and clear. Be sure to place the lid on the can tightly when you are finished. Humidity can cause problems.
How do I thin Aerothane and Ranthane?
For standard suction guns (compressors), thin Aero-Thane 33% (3 parts catalyzed Aero-Thane to one part UE-820 Reducer). For turbine-powered HVLPs, you may need to thin more, up to 40%. For standard suction guns (compressors), thin Ranthane 33% (3 parts catalyzed Ranthane to one part G-4200 Thinner). This is a starting point; you may need more. For both paints, after reducing/thinning, filter through a 60x48-mesh or finer paint strainer cone.
My Poly-Tone has been sitting for over 3 years. Is it still OK to use?
Yes, the guaranteed shelf life is 4 years for Poly-Tone. Just be sure to shake it real good prior to using it.
What is the shelf life of Aerothane and Ranthane paints?
It is also 4 years. Do not store paints in temperatures above 100 degrees F if possible.
How long should I allow the topcoat to dry before I mask off an area for trim colors?
You should allow at least 12 hours of drying time prior to taping; more time is better. This assumes an ambient temperature of 77 degrees Fahrenheit. Cooler temperatures require more drying time. More drying time is always better.
What kind of masking tape should I use to mask off trim colors?
It is very important that you use only a high quality masking tape such as 3M fine line tape. Use of a cheap masking tape will cause bleed through.
What kind of paper should be used to protect painted areas while I am spraying trim colors?
Use a butcher paper or a high quality paper from your local paint store. Do not use newspaper as the print may bleed through onto the surface.