Author Topic: What is your guideline? (Read 3669 times)

wwwarbird · « **on:** June 20, 2011, 01:31:17 PM »

What guideline to some of you use for "it's too humid to paint"?

Too often I feel like I have more trouble with blushing than I should. Literally minutes ago I shot the clear on a plane and it's blushed so badly that it looks like I used flat clear. As soon as I noticed it going I made sure that I got a couple good heavy coats on all the same session because I've gotten away with doing that before.

While spraying it was 69 degrees with 48% humidity in the shop.

Allan Perret · « **Reply #1 on:** June 20, 2011, 01:42:58 PM »

Only time I have been able to spray dope without any blushing (even using retarder) was when humidity was 30% or less.
Thats happens maybe 5 or 6 times a year around here. So lately I have been experimenting with a way to work around (or with) the blushing. Spray more thinner (dry) coats vs fewer wet coats. That will result in more texture of the final surface, you just have to resign to the fact you will have to wet sand and buff to get the gloss.

Randy Powell · « **Reply #2 on:** June 20, 2011, 02:26:35 PM »

Heat's involved, too. I've shot dope successfullyat 80+% humidity, but the temps was down in the 50s. So it's more likely to get blushing if it's hot AND humid. For the past 2 months it's been running between 60% and 90% humidity here.

Bill Little · « **Reply #3 on:** June 20, 2011, 02:44:59 PM »

I think it has a lot to do with the combination of heat and humidity as Randy and others say. A wet bulb and dry bulb reading thingie. Possibly related to "heat index". Although in the VERY odd times that it has been above 90* and below 30% humidity at the same time, spraying dope is almost too easy. Only trouble is not letting it dry before it is on the airframe! LOL!!

Ty, I cannot recall the DuPont number fr the "3600 series" , possibly 3606S. I just wet sand out the blushing in the clear. I don't worry about the colors blushing since the clear usually cures that.

Best scene is using the DuPont Chromabase/Chromaclear system. It doesn't blush! (and takes well less than 1/2 the amount of material as dope does.)

Big Bear

wwwarbird · « **Reply #4 on:** June 20, 2011, 07:00:25 PM »

Thanks guys, I agree with pretty much everything above. I've never really considered the high humidity/lower temperature combo that Randy mentions. Thinking about it that makes sense because in my (basement) shop it seems to stay somewhere between 40 to 50% humidity year 'round, sometimes higher. By memory it does seems like when it's a little cooler down there (winter) I have a lot less trouble.

Now I just have to figure out how to fix this thing.

Allan Perret · « **Reply #5 on:** June 20, 2011, 07:59:26 PM »

OK heres a question about the blushing. I know its caused by moisture, but is it the moisture in the compressed air stream coming out of the gun or the moisture in the ambient shop air. If it is just the moisture in the compressed air steam, then it should be able to eliminated the blushing with a good air dryer. But I know they are expensive..

wwwarbird · « **Reply #6 on:** June 20, 2011, 09:23:32 PM »

Allan,

It's always been my understanding that it's the moisture that gets picked up between the gun and the airplane.

So, I just went down and sprayed about four heavy coats back-to-back of roughly 80% thinner 20% clear on it. One good thing is that I did learn immediately that my normal 50:50 mix is too thick, this mixture sprayed and flowed out MUCH better. Gotta watch for running more carefully, but I liked it a LOT better. Overall the blushing is maybe 5% better right now. My idea and hope is that the thinner will work on it all overnight and it will be ok tomorrow. We'll see.

(If it's not ok tomorrow, this might be the first time I've had to totally succumb to major blushing. If that happens and I should decide to, can you rub it out and still end up with a good shine? If so, what products are recommended?)

Bill Little · « **Reply #7 on:** June 20, 2011, 11:08:08 PM »

If the blushing does not eliminate itself, shoot a coat of thinner, but not too wet. Let that dry for 24 hours and then see how it is. If any is still present, wet sand with 1200-2000 then rub and wax.

A coat of straight thinner can relieve the blushing sometimes since it is simply moisture captured under the film that quickly forms on top. And colors that blush can usually, if not always, be cured by shooting highly thinned clear over them. Any auto paint supplier can give you the next "hotter" grade of thinner (same thing as retarder, basically) in whatever brand of thinner you are using which will increase the drying time and further help to eliminate blushing (allow the moisture escape). I got some "hot" thinner one time and didn't realize it. Made some thin, trim stripe, colors on the bottom of the model disappear before I figured out I had switched thinner. But there was absolutely no blushing!

Big Bear

Mark Scarborough · « **Reply #8 on:** June 21, 2011, 09:52:34 AM »

With all due respect, be carefull with terminology,, a HOTTER thinner is one that dries faster,, for cold temperatures, a COOLER thinner is slower, and is for higher temperatures,, so the distintion needs to be made that you want a thinner for HOTTER air temps, which will be a slower thinner, or a thinner for COOLER air temps which will be a faster thinner.

Randy Powell · « **Reply #9 on:** June 21, 2011, 10:51:12 AM »

Mark, you have a guideline? Wow.

I will say that in some circumstances, I've used a slower thinner in colder temps. This is mostly because the colder temps often don't allow the paint to lay out (I'm talking outside the manufacturer's recommended temp range). I've had some problems sort of like orange peel when the temp is really too cold to shoot and using a very slow thinner allows the paint to lay out and level before it starts to dry. But this is a special case. In general, as Mark notes, it's slow for hot and fast for cold.

wwwarbird · « **Reply #10 on:** June 21, 2011, 05:42:28 PM »

I'm currrently using all Brodak products, including the their thinner which I have to assume is pretty hot/fast.

What would be a recommended cooler/slower thinner I could use straight to spray on top? I have a can of some cheapo NAPA lacquer thinner for cleaning. Maybe I could shoot a coat of it? Are there any standard codes or numbers too look for on that can to tell how fast or slow it might be?

UPDATE...with nothing really to lose, I just sprayed a good heavy dose of the cheapo NAPA thinner (ACME by name actually, for real!) on the separate wing strut assembly. It resulted in no change in appearance at all, if anything it may be worse. I figured since it was made by ACME it would fix things for sure.

I give up, and I hate giving up. Mother Nature is a bitch. I suppose at this point I have to just hang it back on the wall and wait for a good low humidity day to give it a couple good heavy coats of clear. That might be awhile in these parts, like maybe until this fall.

I just hope it works when I do.

bill bischoff · « **Reply #11 on:** June 21, 2011, 08:11:13 PM »

On the profile carrier Hellcat I recently finished, I had this experience and made these observations. I was spraying in my garage in Dallas with the door wide open. The OAT was in the 90's, and the humidity didn't seem too bad (downright arid by Houston standards!). The first coats of Brodak Piper blue were sprayed with an 8 oz touch up gun at about 35 PSI. Plenty 'O blushing. An hour later, the next coat was sprayed with a cheap Badger siphon gun with a 2 oz jar. Perhaps it was the reduced volume of air flowing through the gun, or the fact that I was spraying closer to the surface, or who knows what, but there was no blushing. Two days later I sprayed the clear with the touch up gun. Slightly cooler outside earlier in the day, more reducer in the mix, and still there was blushing. I moved the airplane into the air conditioned house and that seemed to help somewhat. The best thing was that I discovered that a bit of hand polishing with some 3M "Finesse It" swirl remover/ polish got rid of the blushing. I have never rubbed out an airplane finish, so this may be how it usually works. I don't know. I was just happy to be done!

( I have done a couple of rubbed out lacquer finishes on guitars, so that's why I had the Finesse It. That's my story, and I'm stickin' to it!)

Mark Scarborough · « **Reply #12 on:** June 21, 2011, 08:26:43 PM »

Quote from: wwwarbird on June 21, 2011, 05:42:28 PM

I'm currrently using all Brodak products, including the their thinner which I have to assume is pretty hot/fast.

Actually Brodaks thinner is a pretty moderate thinner, I would rate it as mid grade, its a very high quality thinner, but formulated ( as one would expect) for general all around suitablility, which means, to fast for hot weather, to slow for cold weather LOL

Quote from: wwwarbird on June 21, 2011, 05:42:28 PM

What would be a recommended cooler/slower thinner I could use straight to spray on top? I have a can of some cheapo NAPA lacquer thinner for cleaning. Maybe I could shoot a coat of it? Are there any standard codes or numbers too look for on that can to tell how fast or slow it might be?

UPDATE...with nothing really to lose, I just sprayed a good heavy dose of the cheapo NAPA thinner (ACME by name actually, for real!) on the separate wing strut assembly. It resulted in no change in appearance at all, if anything it may be worse. I figured since it was made by ACME it would fix things for sure.

Wayne, not a bad idea, but you are missing the boat there, what you really need is for the surface to stay open longer so that the moisture can escape from inside the paint. a SLOW/hot weather reducer is the ticket. Acme thinner is HOT/ cold conditions thinner, or I would expect it to be. this really wont accomplish anything except to pump extra solvent into the paint which can create issues down the road. What you are trying to accomplish is to allow the paint as you apply it to stay open long enough to allow that moisture trapped in the applied material to evaporate. hence the use of retarder, to keep the surface more to the "fluid" side longer. If you wanted to try the thinner idea, I would use the slowest thinner you have( brodaks apparantly) perhaps add a bit of reducer, then spray that on there. I must confess, I dont like that idea, I would want at least some percentage of clear in what you spray on , the idea of spraying pure thinner onto a dry finish give me the hee bee gee bees,, It can cause the finish layers to separate, blister, or shrink out excessively.

Quote from: wwwarbird on June 21, 2011, 05:42:28 PM

I give up, and I hate giving up. Mother Nature is a bitch. I suppose at this point I have to just hang it back on the wall and wait for a good low humidity day to give it a couple good heavy coats of clear. That might be awhile in these parts, like maybe until this fall. I just hope it works when I do.

Not sure about where you are, but typically early morning is a better time to spray, less humidity

Mark Scarborough · « **Reply #13 on:** June 21, 2011, 08:28:46 PM »

one additional note, typically, cheap thinner is FAST, the slower a thinner is, the more expensive it is,, because the componants that make it up are more expensive,, we call ACME, or other hardware store thinner, Rocket fuel, cause its very very hot, and low quality, usually great for starting fires, or washing the floor or spray guns with,, NOT for use in paint,, at least not paint you want to be shiney, smooth, or look good

wwwarbird · « **Reply #14 on:** June 21, 2011, 10:57:19 PM »

Thanks a bunch for the info and advice guys.

Mark,

Yeah, I'm more or less familiar with the basics, I knew right away that the problem was that it wasn't staying "open" long enough. I didn't have any reducer on hand either, in fact I've never used the stuff. I created the problem myself, I knew going in that it was risky conditions for spraying but I went for it anyway because I was trying to get it finished to bring to the Sig contest this weekend. It was kind of like when you know something is going to hurt, but you go ahead and do it anyway.

Being stubborn, I just tried buffing some areas with a plain dry paper towel. It actually worked pretty good if I rubbed hard enough. I can't rub that hard over the open bays though. If I can come up with some miracle compound it looks like I might actually be able to buff it all out like Bill mentioned above without too much trouble. I've got one more night after work tomorrow to work on it before the weekend so I'm going to look around tomorrow for something to try on it.

Here are a couple photos attempting to show the dull finish. You can really see the line in the elevator/stab photo. The shiny areas in that photo and a small spot on the extreme nose are about the only good spots on the entire plane. Like Randy says, SIGH. $:-\$

Allan Perret · « **Reply #15 on:** June 22, 2011, 06:14:27 AM »

I have checked the humidity thru the course of the day many times. Here in southern Louisiana the lowest is usually between 1 - 4PM. Early mornings the humidity is the highest.

john e. holliday · « **Reply #16 on:** June 22, 2011, 09:20:09 AM »

My "Thirteen" I built for Old Time Stunt looked like it had been painted with milk when I put the last coat of clear on it. This was on the wings and tail surfaces. Finally I sat outside the basement with a jacket on as it was cold and I brushed on another coat of clear dope thinned to 50%. By the time I got every thing cleaned up and back inside the dope was nice an clear/shiny.

Randy Powell · « **Reply #17 on:** June 22, 2011, 09:26:04 AM »

>>I didn't have any reducer on hand either<<

I think you meant retarder.

Looking at it, were it me, I'd shoot a heavily thinned coat of clear on it. Something on the order of 80% thinner/20% clear dope.

wwwarbird · « **Reply #18 on:** June 22, 2011, 06:03:10 PM »

Quote from: Randy Powell on June 22, 2011, 09:26:04 AM

>>I didn't have any reducer on hand either<<

I think you meant retarder.

Looking at it, were it me, I'd shoot a heavily thinned coat of clear on it. Something on the order of 80% thinner/20% clear dope.

DOH! Yeah, I meant retarder. (Too many paint fumes the last few days

)

Mark Scarborough · « **Reply #19 on:** June 22, 2011, 06:06:49 PM »

HMMM retarder,,,
paint fumes,, something slightly ironic about that

Jim Thomerson · « **Reply #20 on:** June 22, 2011, 08:42:59 PM »

We are in extreme drought,, but doubled the year's rain with 2 inches last night. I finally made it out to the shop to brush a coat of butyrate on some recovered wings. It blushed. I brushed on a coat of retarder and the blush went away.
When I lived in a rooming house in college, I decided, although it was misting rain, to go outside to dope a wing. I mixed butyrate with about 50 % retarder and had no trouble with blush.

wwwarbird · « **Reply #21 on:** June 22, 2011, 10:23:32 PM »

Quote from: Mark Scarborough on June 22, 2011, 06:06:49 PM

HMMM retarder,,,
paint fumes,, something slightly ironic about that

Huh?

Well, this time I really did give up. (SIGH)

Tonight I tried rubbing and buffing with a few different compounds and nothing wants to do the miracle. I'm just going to have to give it all a light sanding, wait for a good weather day, and hit it with some more clear.

(BTW Doc, that was a very good potential tip to brush on a coat of clear. For the heck of it I tried it on the bottom of one side of the stab/elevator and it came out real nice and shiny. The thing is that I want to go for the smoother finish by spraying though. Thanks for the tip!)

Mark Scarborough · « **Reply #22 on:** June 22, 2011, 10:33:56 PM »

Wayne, Make sure you give it a pretty thorough clean before you sand, some compounds have stuff that likes to make a mess when you repaint,,

I probably should not poke fun at you,, that just opens the door for you to harass me about some mysterious 109,, or uh something,,?

wwwarbird · « **Reply #23 on:** June 22, 2011, 10:37:05 PM »

Quote from: Mark Scarborough on June 22, 2011, 10:33:56 PM

Wayne, Make sure you give it a pretty thorough clean before you sand, some compounds have stuff that likes to make a mess when you repaint,,

I probably should not poke fun at you,, that just opens the door for you to harass me about some mysterious 109,, or uh something,,?

Yep, I know Mark, thanks for the heads up anyway. A 109? What?

Randy Powell · « **Reply #24 on:** June 23, 2011, 09:51:55 AM »

Wayne,

Mark's had an absolutely awesome BF-109 semi-scale stunter in primer for like 2 years. He keeps threatening to finish it, but so far, it's still in primer. Gives the rest of his stunt buddies lots of tease material.

Mark Scarborough · « **Reply #25 on:** June 23, 2011, 10:09:50 AM »

Randy,
Wayne gives me more crap about it than any of my local buddies do,, hes just very subtle about it, LOL

wwwarbird · « **Reply #26 on:** June 23, 2011, 12:39:58 PM »

Git'er dun Mark!

dennis lipsett · « **Reply #27 on:** June 25, 2011, 04:54:19 PM »

Quote from: wwwarbird on June 20, 2011, 07:00:25 PM

Thanks guys, I agree with pretty much everything above. I've never really considered the high humidity/lower temperature combo that Randy mentions. Thinking about it that makes sense because in my (basement) shop it seems to stay somewhere between 40 to 50% humidity year 'round, sometimes higher. By memory it does seems like when it's a little cooler down there (winter) I have a lot less trouble.

Now I just have to figure out how to fix this thing.

I didn't read through all of the posts but I usually have a dehumidifyer running in my shop when it's hot and wet. Seems to make my life a lot easier and its a fairly cheap fix.
Dennis

wwwarbird · « **Reply #28 on:** June 25, 2011, 10:18:32 PM »

Good idea Dennis, but I do have a dehumidifier running 24/7 through the summer months down there. I can't get it below 50% down there lately though.

Allan Perret · « **Reply #29 on:** July 01, 2011, 04:49:41 AM »

Quote from: Jim Thomerson on June 22, 2011, 08:42:59 PM

We are in extreme drought,, but doubled the year's rain with 2 inches last night. I finally made it out to the shop to brush a coat of butyrate on some recovered wings. It blushed. I brushed on a coat of retarder and the blush went away.

Straight retarder, 100% ?

Randy Powell · « **Reply #30 on:** July 01, 2011, 06:44:54 PM »

I just looked at a list of the 10 most humid cities in the country. 3 of them are within 80 miles of me. Joy!

Just shoot 90/10 thinner to clear on it.

wwwarbird · « **Reply #31 on:** July 01, 2011, 11:06:04 PM »

Quote from: Randy Powell on July 01, 2011, 06:44:54 PM

Just shoot 90/10 thinner to clear on it.

Thanks Randy but I already tried that on the separate wing strut piece as a test and got no change at all. I even tried straight thinner. I'm just going to give it a light wet sand all over and then shoot it with another coat of clear under better conditions. I'm pretty confident it'll work out that way, we'll see. Sigh.

Randy Powell · « **Reply #32 on:** July 02, 2011, 02:29:33 PM »

Sounds like you have a plan.

Steve Helmick · « **Reply #33 on:** July 02, 2011, 04:41:44 PM »

I'd like to hear more about Randy's list of most humid cities. Is there a link to a website? I've lived in Montgomery Alabama, Norfolk Virginia, South Central Tennessee, been to Boston, Florida, Wisconsin, Louisiana, etc. Our humidity is very low compared to all of those. When it's 103F and 99.7% humidity, you'll know it. Any of the above can get there. Normally, we're around 60% in Western Washington, except inside Randy's shop...and tornadoes are really rare!

Steve

Randy Powell · « **Reply #34 on:** July 02, 2011, 07:17:34 PM »

Steve,

The barometer on the side of my shop rarely drops below 70% over the winter. Often near 90%. Better in the summer.

http://web2.airmail.net/danb1/usrecords.htm

Interesting site.

W.D. Roland · « **Reply #35 on:** July 05, 2011, 01:20:32 PM »

Auto lacquer thinner can be bought 3 ways, Fast, Med and Slow.

Slow gives least blush problems.

With fast the moisture is trapped before it can evaporate.

Went looking for some slow today and the auto paint stores only stock fast now as shops only use it for clean up now a days. Fast is cheaper.

Stoped in at auto zone and HA! they have Med thinner so that is what I am stuck with for now.

Randy
A week or so drying time to hopefully let all the moisture out of what you have down might help.

If it blushed in and early coat and you have several coats on top of that then sanding it all off might be the only good solution.

In the past have sometimes brushed on straight thinner a couple of times to help let the moisture out of the paint already in place. Sometimes it worked and sometimes not.

Good Luck!

Bill Hummel · « **Reply #36 on:** July 05, 2011, 01:51:59 PM »

DuPont 3602 S is the "slow" thinner, lots of retarder, useful for humid/hot/high dew point dope painting. I've also had success on the clear coat with Poly Fiber rejuvenator product, used for re-painting old, damaged dope. This product, too, has high retarder %. Nothing works all the time...sometimes you just need to wait it out. I've had no success with all the "hardware store thinners"...

wwwarbird · « **Reply #37 on:** July 05, 2011, 10:41:50 PM »

Quote from: Randy Powell on July 02, 2011, 02:29:33 PM

Sounds like you have a plan.

Yep, I did.

I sent the plane home with Keith Sandberg last Friday when he was in town. He's 100+ miles away from me but his shop has much better climate control than mine. He was able to give it another coat of clear for me. I haven't seen it yet, but he called me today and said it came out good.

...I guess I can't ever enter it at the NATS now though!

john e. holliday · « **Reply #38 on:** July 06, 2011, 08:12:18 AM »

Hey you can't enter any of the age classes, but can enter any PAMPA class with no appearance points. Still don't see people are so picky about someone else doing a final clear coat. Iknow of several that have had the clear coat done and still got appearance points. I don't worry as they still beat me by a bigger margin than the 20 max appearance points.

wwwarbird · « **Reply #39 on:** July 06, 2011, 09:34:52 PM »

Yeah I was just kidding there Doc, couldn't resist tossing that one in.

john e. holliday · « **Reply #40 on:** July 07, 2011, 07:41:34 AM »

Well the skies are dropping moisture all over the place. Will be doing more dope today anyway.

Bill Little · « **Reply #41 on:** July 08, 2011, 12:59:26 PM »

HI Wayne,

I am glad it seems to have finally been taken care of. I thank Mark for the terminology correction, his definition is spot on. We always called the slow drying thinners "Hot" because they will really reach down into lower layers of paint since it dries so much slower.

When "rubbing out" blush" it is imperative that you wet sand first, like I originally said, before hitting it with your rubbing compound. The sanding will cut the top film and let the moisture escape. We are hideously humid here in "Hades, NC" and blushing is something that is a way of life when using dopes and lacquers around here.

On the other hand, when I painted the Argus, using DuPont Chromabase/Chromaclear, it was raining outside and it had no blushing effect on the paint. I wish it wasn't quite so expensive, I would use it for everything! Very, very, little material needed for coverage (less than 5 oz. of mixed green to paint the whole Argus) and the clear lays out so beautifully.

I actually got some NAPA "Econoclear" the last time I bought urethane clear and it works outstanding. It is a 4-1 mix, though and you have to use more clear material than in the 2-1 mixes.

Bill