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DanB
11-27-2008, 01:57 PM
Can someone tell me what the highest humidity percentage would be to still paint the Polly products? We are at 68% right now and I have blush retarder on hand...Just didn't want to spin my wheels.

RandyL
11-27-2008, 03:21 PM
I haven't shot Aerothane yet, but I can tell you that 68% humidity would be no problem for PPG urethanes. I suspect it's fine based on the comments from their web site below...

APPLICATION PROCEDURE: Spray a light color coat, enough for gloss and color, but not enough to run. WAIT until this coat is tacky and transfers no color to your finger. Should take 20 minutes at 77°, longer at cooler temperatures. Don't let this first coat dry completely. Spray a medium coat of paint. This coat should flow out and look wet; again don't flood it on. Now spray a final wet coat for fill and color. Do not flood it on! That's a total of three coats, wet, but not enough to run. These are normal coats, not cross coats. Dry film thickness should be approx. 1.7 mils (.0017). Application in less than 55°F. temperature is not recommended. Do not spray in ambient air temperature above 95°F. due to accelerated polymerization caused by the heat, resulting in reduced gloss. Relative humidity above 80% accelerates polymerization and may reduce gloss if exposed before drying 12 hours.

DanB
11-27-2008, 04:46 PM
Thanks Randy,
Was looking for the info in the book and didn't think to check online. I had a full enough day eating turkey, sanding the wing, and mixing together the 5 gallons of yellow paint. I still have one coat of polyspray, then white, then the yellow. The shaker came to the rescue so no humping it to Home Depot.

RandyL
11-27-2008, 05:19 PM
Dan,

Are you putting on a coat of white Poly Tone so that the yellow will show better? How are you measuring humidity? I never worried about it when painting my RVs and no issue with it. Maybe Aerothane is more sensitive to it.

DanB
11-27-2008, 06:23 PM
I'm actually doing PolyTone for everything. Using the white PolyTone before yellow is suggested as it may be too hard to evenly cover the silver coat. To measure humidity was just looking at the nearby Gateway Airport weather. I've decided to jump into spraying tomorrow and will report on what happens.

RandyL
11-27-2008, 06:43 PM
Pics Dan, we need pics!

n85ae
11-28-2008, 09:31 AM
I painted my entire plane white polytone, and then painted it with Aerothane.
Aerothane is very easy to paint with just a little practice. The runniness
is not different than any other paint. In my experience, fear of runs causes
more problems than anything else, since you tend to underthin, and then you get issues with orange peel.

Here's a shot of my wing during painting:
http://www.aselia.com/n85ae/jeff026.jpg

After looking over Bruce Lina's plane, and despite that my Aerothane came
out as well as it did, were I doing it again I would just stick with Polytone
like Bruce did. It looks good, less shiny, but just as good in it's own way.
Plus a LOT less hassle.

MUCH harder is painting System Three WR-LPU, as I am using to paint
my CH801 project. It's a waterborne polyurethane, and very cranky to
use: http://www.aselia.com/ch801/img2356.jpg It does have the
nice feature that it's low toxicity, and you can drink the solvent.

Regards,
Jeff Hays

DanB
11-28-2008, 02:12 PM
Well, no photos today... seems this was not the day to lay down paint due to several things, but mostly one thing:
Operator error...
I have been very meticulous about cleaning the gun to the extent of taking the air cap and needle valve out and soaking in solvent in between spraying times. That being said, I got things set up to spray today, did my test spray on cardboard and went to the wing. The spray pattern started then stopped within 15 seconds (nuthin but air). I went back to the bench, took the gun appart and cleaned it inside and out. Found out that the screen filter in the bottom of the cup can clog up with gunk even though it looks clean from up top. Cleaned it out good and was sure that was it. Put the paint back in, went to paint, same thing. I finally found that the little air hole in the lid of the cup was clogged. After that, the gun shot fine on the cardboard. By this time I was close to the end of my rope.

The humidity was only 50% and Temp. was a nice 70 degrees. I figured I was in a safety envelope but I still crashed and burned. When I went to spraying, I was introduced to two things I have read about but never met personally... As soon as I sprayed I got orange peel and fish-eye at the same time. I may have had the pressure turned down a bit too much and that probably gave me the OP. The fish-eye is what surprised me because I wiped down the surface with the 2210 prep solvent. I also have an in-line filter right at the gun. I may need to replace my filter and perhaps my hose...at any rate I'm offically calling it a day. Time to go to a movie with the wife.
Cheers :cool:

DanB
11-29-2008, 01:43 PM
There is alot to be said about puting things down and walking away when everything starts going south. Today I walked into the shop and after sanding the boo-boos out from yesterday...I laid down the last cross-coats of Poly Spray in the morning.

207

208

After drying I went after the white Poly Tone which is suggested prior to shooting either yellow or red. I decided to try a trick that Alan Nephews told me about. He said before shooting the color coats, put the paint into the freezer...it doesn't freeze but keeps the paint cool enough to dry slower and gives a glossier finish. The pictures you see below show not a wet coat but the resut I was hoping for with a glossy finish. If you look close enough you can see some tiger stripes, but I was only going for a light coat of white (as per the instructions). I did not cross coat it, so this is encouraging to see even this coat gloss up. The Temp for this was right around 70 and the humidity at 50%. I used the 8500 thinner reducer.

209

210

Will do the yellow tomorrow.

RandyL
11-29-2008, 02:56 PM
Dan,

Nice looking work! Your shop lights look nice too -- I'm sure by now you're glad you took the extra time to put them up. One thing I found me when painting same color coats on top of each other is to keep a small flourescent shop light in my other hand and position so I could see exactly how my paint was going on with the other hand. Might help you when you're putting yellow on top of yellow for example.

Keep up the good work!

DanB
11-29-2008, 06:11 PM
Thanks Randy,
That sounds like a great tip holding a shop light while painting. I will try it for sure as there are always places I just don't get the reflection I need.

DanB
12-02-2008, 07:31 PM
I tought I would follow through and post a couple pics of the first cross coat in yellow. Steve Kellender affectionately calls his paint "Please don't hit me yellow" (Piper yellow)...I think I will have to follow up and call mine Please Please don't hit me yellow ...or translated..."Are You Freakin Blind?" :D
221
222

DanB
12-03-2008, 06:27 AM
Dan, it's starting to look like an airplane. A little each day.
And by the way it's "Don't Kill Me Yellow" but I don't think that's what Poly Fiber calls it.:)
Dan, it wasn't long ago your Kitfox looked like this. A little each day. It's going to turn out great. Nice work.
http://www.teamkitfox.com/Forums/album.php?albumid=15&pictureid=462

Thanks Steve,
Finally seeing a color on it certainly provides inspiration. Thanks for sharing the pic...I hadn't seen that one. :)

Slyfox
12-03-2008, 08:57 AM
I'm new to the group so I say, HI! to everyone.

On painting, I did mine 3 years ago now, the polytone is easy to put on, but doesn't hold up to well, at least for me. I put an average of 250hrs a year on the fox and it shows. The bottom, yuk, and to get the exhaust off, a lot of work. My recomendation is to put the eurothane over the top. If you want to make the polytone shine, the trick is to put I think reducer in it(the stuff you put in for painting in high temps, so it dries slower) and than shoot in 65degree temps, than the drying time is real slow. THan it will shine a little.

My plan is to repaint my airplane after I replace the engine, I WANT THAT 912S, ya baby. But this time I'm going with the Stewart systems, I put it on my newest airplane, RV7A, which is almost ready, you know the 10%left with 90% of my time. This stuff is different to put on, but shines nice and cleanup is a breeze. Not to mention the risk factor is gone while spraying. AFter it dries the MEK won't take it off either.

I don't think the humidity is a problem as much as a cool 65 for spraying. THe slower it dries, the better it looks. Have fun.

Skybolt
12-09-2008, 10:05 PM
Dan B said >>"I decided to try a trick that Alan Nephews told me about. He said before shooting the color coats, put the paint into the freezer...it doesn't freeze"

I have heared this story many times, about placing mixed paint in the refrigerator....not so much the freezer!
If it is a non catalized paint, you will only change the viscosity. Making the paint very thick during spraying. As the paint warms up, this will make the viscosity thinner. So there will be difficulty knowing what is going on with the application.
With 2 component, catalized paints. Placing the mixed paint in a refrigerator will retard the chemical curing reaction. So the pot life is a little longer but can not be measured.
Again, the viscosity is realy heavy at first application.
What can this do for you? provide orange peel. Very heavy application and paint runs when the viscosity changes during the paint warm up.
From my experience, if the paint is at spraying temperature and you add your additives for the temperature per manufacturers recomendation, you will probably have the best results. Unless the coatings company gave you false information.

Note: the new waterborne paints will freeze if you place them in the freezer.

As to humidity when spraying. Good rule is to use a thinner or reducer, whatever the paint is that you are about to spray for the temperature you are spraying in.
High humidity with single component paints (no hardener) you will probably need a retarder to add to the paint. This reduces the risk of blushing.
As solvent evaporates from the coating, this has a cooling effect on the object. This cooling attracts water vapor that is in the air into the paint and you will have slow drying and this blushing or milkiness. The faster the flash off of solvent the more of this problem.
High humidity with two component paints (hardener required) Again, use the reducer or activator for the spraying temperature. Do not under-reduce or place the paint in the refrigerator as this has a thickening effect and you will be more prone to solvent pops as the water vapor enters the coating.

The problem normally faced whan spraying in high humidity conditions is the paint taking too long to flash (this is because there is no room in the air for solvent evaporation, it is saturated with water) Do not be tempted to use a fast reducer as this normally has the bad effect of causing solvent pops. (remember the faster the evaporation the more cooling effect and then the more problem of moisture entering the film. much like the water that collects on a soda can when you take it out from the refrigerator on a humid day.)

If you do not have the best conditions to spray a two component paint, wait until the conditions are more favourable.

Eric.

DanB
12-10-2008, 07:38 PM
Eric,
Thanks for the reply and comments. You are actually the second person that has told me cooling down the Poly Tone will do no good. Cooling down the product is more than just a "story" as it is recommended in the Poly Fiber manual (P.82). Granted, it says the refrigerator, but I thought I would try something someone had success with. I will be the first to point out that I am new to painting and I am learning quite a bit as I go along...So it's all good.

From what information I can gather, there is one major thing that will make the finish glossier...slowing down the dry time. Two things are said to affect the dry time...1. Temperature 2. Adding Blush Retarder. The logic of cooling down the paint seemed reasonable to me and I have been using 8500 reducer (which just has more blush retarder compared to the R 65-75).

The concern of increasing the viscosity of the Poly Fiber Product is nill. If there is a change, it is not noticeable and though I have been learning my gun, it has been spraying quite nicely. The only thing I found I needed to pay attention to using near freezing paint is to watch for condensation buildup on the paint cup. At one point I had a water drip onto my paint...not a fun experience. :o

As I have had fairly good success with my paint job to this point, I see no reason to fix what aint broken, however, I am a bit curious now. The question is...can I produce the same finish I am currently getting without freezing the paint? I guess I will have to try it and report back.
Over and Out

Skybolt
12-11-2008, 04:33 AM
Hi Dan.
It looks like you are learning the painting process quite well:)
I kind of agree with you.. from what you said above, If every thing is going and looking good, then why change?
The thing is with paint, if there is a problem it will either be an imediate problem or something that shows up later. Immediate= blushing, orange peel, craters (fish eyes), paint runs, solvent pops, lifting, bad or no drying.
Later= crazing, peeling, low gloss, staining.
Most paint problems are self inflicted. Preparation was not adequate, paint was not mixed correctly, application and equipment was poor, application environment was not adequate and post application mainenance was not good.

As to the Poly Fiber manual (P.82). They suggest or recommend placing the mixed paint in the refrigerator. I don't have the manual handy, do they say why they suggest or recommend this?

With Polytone, an air drying (not a chemical reaction) paint. All benifit from good quality solvents that are used for thinning and slow drying. So' in theory a slower thinner or even a retarder will boost the gloss. Not only this but you should also notice an easier application (keeping a wet edge) better underspray and overspray melt in and a far smoother paint job...less dusty and less orange peel effect.
I personally do not see why refrigerating the paint can help with these things.

Anyone reading this; it is so important to follow the technical data sheets of the paint materials that you will use.
Before application, make sure the environment is satisfactory. For your health and or the sake of the paint.

Eric.

n85ae
12-11-2008, 07:56 AM
I took so long painting various parts, that I painted in everything from hot
humid 80's, to cold down to about 50. I like painting in the cold weather
better. The only probelm is it take a lot longer for the Aerothane to cure.
It still cures fine, and after 6 years mine still looks like new.

Regards, Jeff

Skybolt
12-11-2008, 11:27 AM
I have painted cars in your area and also down in Houston. Years ago I painted in the middle and far east. I understand the conditions. Summertime, probably the most comfortable time to spray paint is early morning and before the moisture build up at mid day and showers in the afternoon.
Polytone is much like laquer, that was used to refinish cars in the old days;
air drying and sensitive to heat and humidity during application.
Always important is to choose the thinner / reducer for the temperature your spraying in. That would mean you will be using a slow solvent.

Now with the high relative humidity, this will be somewhat of a balancing act. First the humidity will slow down the evaporation of the solvents =if the air is saturated (with water)then there is not much room for the solvents to go too freely. If you have good ventilation (air movement taking the solvents away) during spraying and flash off this will speed up the evaporation time (or drying)
If you are starting to get milkiness in the paint (blushing) this is when you need a slower solvent or retarder. Because if the paint surface is starting to flash (form a skin) Remember, that there is a cooling down of the coating and object during evaporation and if there is too much water in the air you will reach a dew point on the surfave and this is the blushing.
A retarder (apart from other uses) will allow the coating to evaporate slower and therefore the coating does not get as cold =more resistant to hitting the dew point.

Hope this helps. Eric.

n85ae
12-12-2008, 08:00 AM
Personally, I'd just get out the paint gun on the worst possible day and
spray some test panel and see what happened. Worst case with polytone,
you end up spraying another crosscoat anyway. Even if you do get some
blush, no big deal to hit it again later.

Aerothane on the other hand is a big pain with the waiting, and sanding
between coats.

Regards,
Jeff

Skybolt
12-13-2008, 04:30 AM
Hi Jeff.
Make sure the water is out of the previouse coat (the one that has blushed) before hitting it again later. Could have later peeling / adhesion problems.

Why do you say that Aerothane is a big pain?
What is the waiting?
Why is there sanding between coats?

Cheers Eric.

Dave S
02-02-2009, 12:47 PM
The partial explanation as to why chilled paint produces a glossier finish is - the lower temp reduces the evaporation rate of the solvents in the paint giving the paint a bit more time to flow out and run together before it sets up. Also - to some extent - this will may slow the evaporation rate to help deal with elevated humidity - hopefully keeping the surface of the paint from chilling below the dew point and possibly avoiding the sugar frosted flake deal.

The general principal is anything that reduces the evaporation rate of the solvents in the paint will have the effect of producing a glossier finish - within limits; such as, lower temp of the paint, lower ambient temp, slower evaporating dilution solvent (which is the reason for the availability thinners of different evaporation rates) coarser spray droplets (which can have other bad effects if taken to extremes), holding the gun closer to the surface - all of these things will have an effect of giving the paint longer to run together before it sets up. Then consider the opposite happens if a person goes the other way i.e. higher temps, smaller spray droplets, faster evaporating solvent & holding the gun further away from the surface.

There is a ton more to the issue when dealing with humidity - such as quick solvent evaporation can easily chill the surface below the dew point where the end result can resemble a sugar frosted flake because of the moisture condensation on the surface of the paint. Mainly this is dealt with by using additives like retarders along with slower evaporating solvents.

Urethane behaves differently than polytone (which acts a lot like lacquer).

When a person considers all of the variables like gun air pressure, flow rate of the paint through the gun, air temp, paint temp, viscosity of the paint, solvent, how close the gun is held , different paint types - it is almost enough to make a person's head hurt thinking about it. Annnnnnd......I probably forgot about a dozen other variables in the process too.;)

What always seems to work best for a starting point is the paint manufacturers instruction - then do some trials and experimenting - as much as it is all supposed to be science - there seems to be some art and voodoo involved with painting too.

Dave S
St Paul, MN

Skybolt
02-03-2009, 05:25 AM
Quote from Dave ..[What always seems to work best for a starting point is the paint manufacturers instruction - then do some trials and experimenting - as much as it is all supposed to be science - there seems to be some art and voodoo involved with painting too.

Dave S
St Paul, MN] end quote.

Dave you are correct.
Start off with the instructions from paint manufacturer.
Try to understand what is going on around the process. If you have never touched a spray gun do some trials before anything else.

Maybe try this...stop by a friendly car repair facility. (a small independant owner shop is your best bet.) Introduce yourself and explain you are about to spray paint for the first time on an aircraft.
Offer him $100 (in twenties) In return for a little eduction with urethane paints and the application of. If you too guys hit it off good at the greeting, he will be your best friend during the painting. And if he introduces you to his spray technician for advice; you are on a roll.
PS. Dont go in there on a Monday morning, probably early afternoon Friday is your best time.

I have been in the car refinishing paint business for over 40 years. Reading the tech data sheets is very important. But these do not teach you to paint, The same thing, if you purchased a welder and read the books; will you be able to weld?
As in welding and painting, there is an understanding (voodoo) and art involved. And there is also a challenge involved if you want to do it, but think of the satisfaction....thats one of the reasons we build airplanes :)

Eric.

DanB
04-25-2009, 09:52 AM
I'm back at it after too many setbacks to mention. The only one I thought would be worthy of posting here is a costly lesson I have learned. Probably not unlike many of you, I tend to be on the meticulous end of the building spectrum. The old addage of analisis paralysis fits me and has taken it's toll in the painting department. I have tried to do things the right way by purchasing "quality" equipment such as my Binks HVLP. I found it on Craigs list which was my first mistake. I thought i was getting a great deal when I paid $150 for a $300 gun. As it turned out, either the air cap or the needle valve (or both) was dammaged. I'm not interested in anyone trying to help me analize the problem because frankly Scarlett , I don't give a damn.
I know if I purchased it new this post would not be here. After many "hair-pulling" sessions, I took the advice I was given at the beginning of my painting and went down to Harbour Freight and bought the $40 HVLP they have (Central Pneumatic Model 66222). This morning I walked out to the booth, mixed the paint, put it in the gun, did a few test sprays and away I went. It was like night and day. I put the paint down like I have been doing it all my life.
Yes Virginia, there is a spray gun Santa Clause and he lives at Harbour Freight.

Slyfox
04-25-2009, 12:17 PM
Well, I think it really doesn't matter to much on the gun, but the person spraying, to a point anyway. I will say, humidity while painting, the heading on this post is very very important. Spray when it's over 50percent and you might as well throw the paint down the toilet. I've wasted many of paint this winter wanting to get r done and having the humidity up, just plain wasted the day and the paint. Do yourself a favor and look on the http://weather.noaa.gov/weather/current/KSFF.html for your airports local weather. Just fill in your airports identifier. In it is the relative humidity. Very usefull. My paint jobs come out when it's around 35 or below. If it's never that low where you are, you will need to get a hold of the paint manufacture and figure out how to paint in higher.

Lion8
09-25-2009, 11:46 AM
Paint related question. I have alot of experience painting autos,not airplanes. Are there any problems repainting a Kitfox? Do you strip off the paint? (Weight consideration?)

Dave S
09-26-2009, 10:27 AM
Hi Tom,

If a person is repainting a fabric airplane - my suggestion would be to determine what the airplane is covered and painted with already and then check the manufacturer of cover/paint system for advice. If it is covered with the polyfiber - they have an excellent book about using their products which I would recommend - the book includes topics on repair/touchup and repainting. For poly fiber - it matters if you have the polytone (which behaves much like lacquer and very easy to renew/repair/refinish) or Aerothane (which is their two part urethane). Since you have worked with Auto paint - you have a leg up on the deal. From what I can tell - the primary difference between auto and aircraft paint systems is aircraft systems have less "fillers" in the formulation - go on a little thinner and are more resistant to cracking - shouldn't use auto urethane on fabric airplanes - I am told.

Theoretically, polytone could be ragged down with solvent and dissolved off the aircraft down to the fabric so a person can sort of start from the base coat - certainly a stinky outside job. Can't do that with aerothane - (maybe I shouldn't say can't - but I believe stripping aerothane would involve more pain and suffering than I ever wish to endure).

We went with aerothane; and, I have decided that 20 years from now when the fabric should be replaced is the next time I will even consider painting it. On a car, a solid layer of urethane, properly watersanded and cleaned up is an excellent base for a new coat - on a fabric airplane with urethane - I'd be reluctant to try it because of the thickness of the final paint and my (warranted or not) paranoia about a surface with as much flex as fabric possibly cracking with many layers - but I am sure there is a way and I am sure someone has done it. Again - finding the manual for the paint system and talking to a knowlegeable distributor about it really helps. Got lots of tips from my poly fiber rep back here.

Sincerely,

Dave S