Author Topic: Paint problems! (Read 1835 times)

steve pagano · « **on:** September 05, 2007, 12:22:58 PM »

Hello gents

Lately when i paint i get a beautiful shine but after it dries it gets dull and full of blotches. I usual use a mixture of 60-40 with a little retarder. Brodak dope of course.

Any suggestion?

T.I.A.
-Steve

Randy Powell · « **Reply #1 on:** September 05, 2007, 12:28:27 PM »

Steve,

There are a lot of things that can cause the problem. Usually it's too much retarder or shooting in to humid conditions or something. You can try a test on the bottom on one of the splotches. Lightly sand it with fine grit paper (maybe 800 or 1000 grit) until it's dulled out. Let it sit for a bit and see if it clears up. Sometimes breaking the surface allows trapped water to escape. then use some rubbing and finishing compound to buff it up.

steve pagano · « **Reply #2 on:** September 05, 2007, 12:40:27 PM »

Randy

what do you use to buff it out ?

steve pagano · « **Reply #3 on:** September 05, 2007, 01:24:09 PM »

Thanks Ty

Got another rookie question! What's the best amount of time to wait after giving a coat of color to apply clear?

P.S. Anybody use retarder when spraying clear?

Leester · « **Reply #4 on:** September 05, 2007, 03:06:02 PM »

Steve: Usually I wait about a week, and that's because of either limited time or crappy weather. You want the paint to dry as much as possible. As far as retarder in clear, only when it's absolutley necessary. It doesn't hurt anything ( some canopys it will ) just my preference.

Chuck Feldman · « **Reply #5 on:** September 05, 2007, 03:21:58 PM »

Retarder is a big problem. Best to never use it. When paint is drying it makes the surface cooler than the surrounding air. If the dew point is the same or higher than the surface temperature you will condense water into or on the finish. (blush) Always paint with the lowest humidity this is usually about 2:00pm. If you get a blush you can wait for good air and then spray it again too release the water and remove the blush. This is a hard problem to solve in areas where humidity runs on the high side.

Alcohol has an affinity for water. I have never tried this but if you wet a tissue with alcohol and lightly rub it on the blush it might just remove the water? I never tried this as I just now thought of it.

Chuck Feldman
Stuart, Fl.

Bill Little · « **Reply #6 on:** September 05, 2007, 03:30:29 PM »

Rubbing (wet sanding then a coumpound) removes blushing. And sometimes just the clear application (if the humidty is low) will remove blushing.

Once color is on the plane, I never use any sandpaper that is courser than 800 grit. I usually start with 1000-1200 and work up to 2000.

Like Ty said, the finish will only have a super glossy smooth look if you have the substrate smooth! Gloss increases the "flatter" (smoother) you can make the surface. Flat paints are so because they dry with a "rough surface" which refracts the light off of it instead of reflecting the light.

Tom Perry · « **Reply #7 on:** September 05, 2007, 04:33:15 PM »

Steve,

A picture may help one of us in trying to resolve the problem. Describing the problem as a blotch could be a lot of different things. For instance my son described the problem he was having when painting a table top as a blotch. When I finally got over to his place to look at it is was really fisheye caused by silicone still remaining on the table after refinishing. In his case some fisheye remover in is laquer cured the problem. It is possible that your original surface could have been poluted from a little oil, silicone, or even oil from handling it. The surface you are painting should be as pristine as you can get it.

The last time I had a problem it was from SWMBO using an air freshener in my work area. It took a while to figure that one out. God bless her she was just trying to help out but It sure screwed up the process for that planes paint job.

Randy Powell · « **Reply #8 on:** September 05, 2007, 05:13:29 PM »

Steve,

I use 3M Rubbing compound (liquid) and 3M Finishing compound (also liquid) then usually a show hand glaze like Maguires or Aurora. Then wax it up.

As Tom notes, it could be anything. If you are talking about a sort of cloudiness, then it is probably blush and you can sand the surface to break seal and it will sometimes resolve. Or Ty's suggestion also works of shooting a solution of just a little dope and mostly thinner. That also will allow the water to escape. The cloudiness is from water trapped in the clear. But it could be other things and a picture would help.

Mark Scarborough · « **Reply #9 on:** September 05, 2007, 05:46:59 PM »

If it is a texture type of imperfectio that shows up after some time drying, then most likely you are trapping solvents. The material skins over quickly (to fast of reducer) and then as time goes the remaining solvents evaporate and the "hard" top skin kind of falls down to fill the void thus a rough texture. In the trade its called "die back". Just another possibility. Truthfully, to diagnose paint problems it really helps to know the facts man,, the facts
air temp
type paint
type solvent
type gun
humidity
gun pressure
tip to surface distance
dry time between coats
what color socks you were wearing that day
and the list goes on
um yeah just kidding about the socks,, its really about what shirt you wear

steve pagano · « **Reply #10 on:** September 05, 2007, 07:31:38 PM »

OK guys hope these pictures go through. I really couldn't get a goo pic of the blotch but you can see a little bit of something.

Here's what I'm working with

15-20 psi on the compressor

6-8 inches from tip to surface

My gun is an 8oz automotive touch up gun from lowes.

My compressor is a 5 gallon Porter Cable nail gun compressor

Using brodak dope (Bellanca Orange)

not sure of the temp in the work shop but its not hot and no humidity.
While i paint i always keep a window fan going in reverse in the window to suck out the fumes.

Mark Scarborough · « **Reply #11 on:** September 05, 2007, 07:43:28 PM »

Steve,
the picts didnt make it however, based on what you said, it sounds more like trapped solvents than traditional blushing to me. several things contribute, stacking to much material on to fast is a prime way to get blushing. If you dont have the mix right and pressure right to get it to flow, the tendancy is to put more material on so it flows. what this does is like I said, it allows the material to skin over and trap solvents, then as the solvents evaporate, it will shrink back giving a really grainy appearance and texture generally a little finer than normal orange peel. It will also tend to look a little "sharper" than orange peel that you would see right out of the gun. were it me, I would sand with 600 after a day, let it dry another day sand again to remove the texture and respray being more worried about coverage than gloss. Use clear for gloss.

Patrick Rowan · « **Reply #12 on:** September 05, 2007, 10:14:53 PM »

"My compressor is a 5 gallon Porter Cable nail gun compressor"

This could be your problem.

Larger compressors allow humidity to turn to water on the bottem of the tank.

Mark Scarborough · « **Reply #13 on:** September 05, 2007, 10:45:43 PM »

very valid point Patrick, compressor probably workint all the time and the condensation could sneak through the lines. A good inline drier would help were that the case, a bigger tank would help MORE. I guess we still havent really established whether the problem is blushing or die back so its kinda hard to really say with certainty

steve pagano · « **Reply #14 on:** September 05, 2007, 11:13:13 PM »

Quote from: Patrick Rowan on September 05, 2007, 10:14:53 PM

"My compressor is a 5 gallon Porter Cable nail gun compressor"

This could be your problem.

Larger compressors allow humidity to turn to water on the bottem of the tank.

I totally forgot!!!!!!!!!!!!!
The other day i was letting all the air out and my hand got soaked! I gotta find out were i can get a water trap. About 2 years ago i asked windy if that would be a problem he said ''just add more retarder'' I guess he's got a bigger compressor.

Bill Little · « **Reply #15 on:** September 06, 2007, 12:10:22 AM »

What Mark said in reference to "GLOSS" is a point many new painters have to learn the hard way. Dope (or most ANY Lacquer) does not want to be REAL glossy in and of itself. The clear usually has a better gloss, but "rubbing out" the plane is what really gives the paint the gloss if everything else is done properly.

Automotive urethane clear top coat is VERY Glossy right out of the gun, but it ain't a lacquer!

Chuck Feldman · « **Reply #16 on:** September 06, 2007, 05:41:12 AM »

This is a very good thread, thanks to all for your input Now about water in the compressor tank. I worked in the process industry all my life. I am an instrument technician. Therefore I understand compressed air more than the average person. When air is drawn into the compressor and goes into the tank water can form in the tank bottom as the air cools. (condensation) As air is taken out of the tank and goes through a pressure reduction water vapor that is in the air will condense and return to water. If this is happening then you will be supply water in the air spray as your painting. The explanation of this in technical terms is lenghty so I am avoiding it. Here at home I do not have the equipment needed to to test the Dew point of the compressed air in my tank. So all I can do is bleed the air tank from time to time. I also run the spray gun with out paint in it and watch and feel the the air coming from the nozzle. It should be invisible. Water vapor is too though. I also spray the air on my hand to feel the temperature of it. My thinking is if it is really cool to the touch it has water evaporating from it. Another thing you can do is spray it (empty) on a piece of paper and see if there is any wetness. WINDY says add retarder all the time. I think that is a simplification and not a good answer. True he knows what he is doing but simply saying add more retarder is a very general thing.
I have found that retarder is not the answer at all. The answer is the right weather conditions and dry air for the spray gun.

Chuck Feldman
Stuart, fl.

Mark Scarborough · « **Reply #17 on:** September 06, 2007, 07:59:45 AM »

Further on the water subject. Just because you arent getting a buildup of water in yoru tank, especially with a small tank that the compressor runs most of the time, It doesnt mean you dont hav ea problem. The air never cools from the time its compressed untill it leaves the gun with small compressors and it will be introduced into the paint air mix. This could be a reason for blushing as well even though there is relativly minor levels of humidity. I have observed another problem but it is pretty obvious, that is the air hose resting on a concrete floor will cool the air and allow condensation of the air in the line that didnt occur in the compressor. Still not sure that what he is describing is blushing though. However all the information posted on this thread IS valid and good to know so regardless its helpfull to someone I am sure. As a proffesional painter for over 20 years, water is one of the worst enemys of a good paint job. dust can be polished out mostlyl, but water,, yech,, the only worse thing is silicone.

steve pagano · « **Reply #18 on:** September 06, 2007, 11:13:48 AM »

Well i had been adding only a couple of drops of retarder but windy suggested adding about 5% retarder to your entire mix. So i came out with 65-35 mix 60 being thinner, 5 being retarder, 35 being dope .

Randy Powell · « **Reply #19 on:** September 06, 2007, 10:54:52 PM »

Yea, I open the draincock after every use and have a dehumidifier (watertrap) in the line. Did all that the first time I got water splatter through the gun. That was fun. I just use a little Craftsman compressor. Works pretty well overall.