Tech Questions - Spraying coats of Poly-Brush


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I thought we were supposed to brush on Poly-Brush. Now you are talking about spraying it on. What's the deal?

The first coat of Poly-Brush must be brushed on the surface. After that, you will want to spray additional coats. That will prevent brush marks from showing through on the final finish.

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I have never sprayed anything before. Should I find someone to spray this on for me?

You will find that with a little practice you can spray Poly-Brush very easily. It is a viscous material not prone to runs. Practice spraying on pieces of cardboard, wood, practice fabric panels, etc. before you begin on the real thing. Pick a small part such as an elevator on which to start. Within a short period of time you will be spraying like a pro.

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What kind of spray gun should I use?

We recommend one of the HVLP (High Volume Low Pressure) spray outfits. They are easy to work with and use a lot less material than a pressure gun. Regardless of what you use be sure the equipment is of good quality. A cheap spray gun will cause a lot of problems.

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Should I wear anything to protect my lungs while spraying?

Absolutely! Be sure you wear at least a high quality, organic vapor, charcoal filtered respirator. If you have a fresh air breathing system then use it. Protect your lungs from the spray mist.

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Do I have to have a spray booth to apply Poly-Brush?

No, it would be nice if you did but not necessary. Just remember you will get overspray on objects around where you are spraying. Be sure the area is well ventilated and that you have plenty of light.

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Should I thin it before spraying it on?

Yes, thin it 1 part reducer to 3 parts of Poly-Brush. Take a paint stick and mark 4 equal marks on it using a magic marker. Then you can pour Poly-Brush up to the 3rd mark and then reducer up to the 4th mark. You now have a 3 to 1 ratio.

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What type of reducer should I use?

If the temperature is below 85 degrees F then use R65-75 reducer. If above 85 degrees F use R8500 reducer.

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What is the minimum temperature I should have before I spray Poly-Brush?

The absolute minimum temperature to spray is 60 degrees F.

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How many coats of Poly-Brush should I spray on?

We recommend a minimum of 2 sprayed on coats, not cross coats. Start by spraying a medium coat. Wait at least two hours, then spray another coat.

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When I sprayed on the first coat it dried rough like sandpaper. What's wrong?

Excessive heat or inadequate thinning is causing the Poly-Brush to dry before it reaches the surface. Add about 2 ounces of retarder BR8600 to each quart of reduced Poly-Brush.

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While I was spraying I got a run on the piece. Should I try to remove it?

If you see the run while it is wet use reducer on a brush and immediately brush it out. If it is dry then carefully wipe it off with reducer on a rag. You must then respray over the area. You cannot sand Poly-Brush. You must get the run removed before going on.

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While spraying the leading edge of my wing, I noticed small pinholes forming. What should I do?

To fix pinholes you must rub the area with a soft cloth and some reducer. The rubbing action will soften the Poly-Brush forcing it into the unfilled weave. Then respray the area with Poly-Brush adding 1-2 ounces of retarder.

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How long should I wait between coats?

Let the first coat of sprayed on Poly-Brush dry at least 2 hours before applying the second coat. After the second coat, allow the surface to dry overnight.

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I can only spray one side of a wing at a time. My wings are on sawhorses. How long should I let one surface dry before turning it over to do the other side?

Let it dry at least overnight before moving it. This will preclude any indentations on the newly sprayed side.

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