Do’s Don’t’s & What If’s of Paint

[SoloQue]

Below are some of the things I have encountered or observed while working in a paint lab. Some of these items might be common sense and some might be pretty useful for trouble shooting. I’ll just list everything out and let y’all sort it through.
The best way to get good spray application is through practice. Whatever method you chose stick with it and remove any variables you can so that you can work on your technique and not have to factor in outside influences. Buy the same brand of paint once you find one you like and write down the guns settings you use when spraying. Humidity and extreme temps will change the way paint performs. If you get a level environment then you can work on application. The goal in my opinion is a single coat application that gives total uniform coverage. A one coat application does not mean a single spray pass application. In reality you want to aim for 4 – 5 spray passes with the paint with maybe only 1 or 2 seconds between passes. This will allow the paint to bond into a single layer and cure out evenly.
Technique – Do a few test sprays to see if the paint is forming a nice fan or cone coming out of the nozzle. If using a gun always run about 10 seconds through the nozzle to purge anything from previous usage. Target the area off to the side from where you intend to paint, start the arm sweep towards to be sprayed area and start actually spraying before you aiming at the actual spray area. Continue the sweep past the target area before you stop spraying. Basically you always start moving your spray arm before you start spraying and you are only spraying when your hand is moving and never start the paint spray over the actual target area but instead just outside the area. This will give you a better chance of laying down a smooth even coat, building with each pass
Working at the top corner of the area to be painted (left or right it’s up to you). Start your first few passes continuing off each side of the target area with each sweep. On these first sweeps you are actually over spraying off the top of the target area. On sweep 2 or 3 depending on how heavy you are applying drop down about a 3rd of the area you are covering and start the count over. Repeat this overlap process until you reach the bottom and actually end up with the lowest part of your spray being off the bottom of the target area. This gradual overlap should help prevent heavy spots or the tendency to overspray a given area. Let this initial full coat sit 30 seconds and look for shallow or light areas where the color is not full or uniform. Hopefully you will not see any of the defects listed below and if you do see light areas pull back a bit farther than before and with the sweeping motion “dust” those areas with a few sweeps. This is when you will be tempted to overkill the spray application or “spot” spray without moving the gun or can which will almost always puddle or drip.
Thickness / Viscosity – In order to consistently spray a good coat of paint you will need to have a consistent thickness of paint. If you had access to a lab there are multiple tools out there to measure thickness but for the purpose of these guidelines we will just use a tongue blade. (pop-sicle stick)
Temperature has a big impact on paint thickness so like I said earlier aim for testing the paint under similar temps every time. If it is a little cold outside you can set the paint can in some warm water to get it around 75 – 77F. Dip the stick into the paint and see if it wants to stand up on its own. If this happens then I’m pretty sure it is too thick. If the stick wants to quickly slip to one side then the paint is on the thin side. Check the bottom of the can for settlement, if present just mix it in. (At this point you can either mechanically mix the paint until the thinner burns off or you can go ahead with the spray by intentionally backing off on the distance to the target and make a few more passes. To get a numerical idea of just how thick your paint is push the stick down until all but the top inch is immersed and pulled up quickly. As soon as the bottom of the stick clears the paint surface start counting. The count stops when you see the first real break or drip in the falling paint. The good thing about this is that you can record that number and you can have a target for future sprays. I did a few pop-sicle tests and 9 – 12 seconds (@ 77F) continuous drip time should give you a good thickness. To be honest the target here is to give you a chance to measure what you are using and be able to reproduce this thickness on future sprays. You can decide what number works best for your own spray technique.
Thinning – Anytime you are going to thin a paint with something that is not specifically listed on the paint container itself I would recommend pouring off a small amount into a cup and add a generous amount of the intended thinner. If you see strings or moss-like pieces form as you stir in the thinner or the whole thing snots up you are trying to use a non-compatible solvent which will ruin your paint. Not all pigments or resins work with all solvents so a little trial and error is advised Probably one of the most universal is Acetone but it has limits
Acetone – Try thinning in 1% by weight increments. A 5% adjustment by weight using Acetone should be easily noticed and is probably the most you would need unless your paint is extremely old and thick. Be careful using too much Acetone, it flashes so fast that the top layer of your paint can “flash” cure (like a tacky top skin) which will trap the other solvents needing to work to the surface as the paint dries. This can lead to blisters once it has cured. Acetone might not be your best bet on really hot days since it will be flashing so quickly that the paint won’t get a chance to lie down so to speak as it dries
Toluene – Another good solvent for thinning with a higher flashpoint. Toluene is a wetting solvent that will not thin as drastically as Acetone but can help with smooth lay down of the paint
Xylenes – Be careful using Xylene for thinning if you are spraying colors. Thinning with Xylene can cause colors to fall out and what you end up with could be visually off from what you thought you were spraying. The bad part is that it will not become apparent until the paint starts to dry. Especially true with yellows for some reason
Thinning with Heat – If you don’t have anything to thin with but you feel the paint is on the thick side you can put the can in some hot water and heat it up to around 90 – 95f. This will allow you to get the paint sprayed and improve the application. This is a thin and go situation since leaving a can open at elevated temps will change the properties of your paint. Keep in mind that at 95F you are probably flashing off some of the solvents and you will need to keep the 4 – 5 passes fairly quick to prevent the layers from flashing and getting tacky which will trap moisture. Note: Most paints are not made with a single solvent, they are a blend of materials that burn off at unique temperatures. To intentionally raise the paint temp will not flash off the components equally and will effect cure rates and long term performance. (lab talk there but useful to understand the effects of over heating)
Paper Cone Filters - Anytime you are using a paint gun I would recommend running the paint through a paper filter cone before actually trying to apply. You will keep your sprays more uniform and have a better chance of a good final appearance
Defects Paint Thickness – Biggest contributing issue to poor appearance is over application
If you can see the paint rolling onto itself as you spray then you are too close.
Runs - If as you spray you can visually see the paint sag or form curtains or droplets while you are spraying you are either too close or moving too slow across the target area. You might have over thinned and need to back up or move faster
Puddles - If the paint seems to sit almost like a puddle instead of lying flat as you spray then either the paint is too thick or it is too cold to be spraying or you are spraying too slowly
Craters or Pinholes as paint dries. These are air pockets that are rising to the surface because the paint is on too heavy. Causes: Spraying to slow, spraying too close, Air pressure is too low (you have to have pressure high enough to fan out the paint and not allow it to come out in globs) or your gun needs adjusting
Orange Peeling – The wet or tacky paint surface looks like an orange peel. Many causes: Your paint might be thinned with a solvent that is flashing off to quickly and not allowing an even drying. The paint is too heavy and is drawing in unevenly as it tries to dry or air pressure might be too low and the paint is clumping as it is sprayed
Mudcracking – The paint looks just like an old mud puddle that has dried up and has cracks running every direction. Causes: paint applied too heavy, paint was not mixed properly, too many coats applied too quickly. Can also mean you added too much hardener and the paint cannot lay flat or is not curing evenly. Anytime you have decided to use hardeners you should allow for extra time between coats or if at all possible make the application a 1 coat process and allow for extended drying time
Fisheyes – These are empty bare holes on the metal like the paint has drawn back on itself. Cause: contamination. Either you have oily/greasy metal or your paint has been contaminated. Check your air line for oil or verify that you thinned correctly. If this happens you can let the area dry and then lightly apply layers over the fisheye area to layer it all out but it will be a long process. You might be better off letting the area dry and just sand it off to start over
Blisters or Pimples - small raised areas with paint still intact over the area. This usually means you have trapped moisture that didn’t get all the way out when the paint was curing. Causes: High humidity during spraying, dirty-oily metal, multiple coats and not letting lower coats dry enough. These can actually break open or fully pop off later leaving the metal exposed
Striping – Paint is not applying uniformly with heavy and light lines on your passes. Check the gun or spray nozzle for cleanliness
Grits and Bits – Could be dried bits or flakes that fell into the paint when mixing or if you added hardener it might need more agitation. Paint needs to be ran through a filter. If you filtered already check the surface being painted for dust.
Soft Mushy Surface – Paint is not fully cured. Could be overall too much paint applied. If a thinner was used the top surface might have flashed over and is preventing the lower layers from drying out. Sometimes the addition of hardener will slow the curing process and you just have to let it sit longer than usual. Could be too cold for painting or humidity is too high to allow for a good cure. This will work itself out with time but the painted area is prone to smudging or actually being scraped off if the paint is bumped or touched.
Transparent Appearance – Paint needs to be mixed thoroughly, the pigment has settled out. Hopefully you will notice the lack of color quickly and be able to wipe off and start over

Safety
Paint fumes are often heavier than air – ignition sources on the floor are hazardous. If you are spraying paint indoors be mindful of pilot lights on hot water heaters and heaters in general that are positioned along the floor
Spraying paint generates static electricity and paint in a vapor form is at its highest flammability potential since oxygen levels are so high – ground your guns (run a wire with alligator clips from your gun to the tank you are spraying. Not all that common of a situation but we have had spray booth explosions that were linked back to static.

Hardeners
When adding hardeners, there is almost always a trade off taking place in performance. While hardeners offer protection from scratches they also increase how brittle the paint coating is when dried and you lose a portion of the adhesion to the metal you are covering. Too much hardener will allow the paint to crack and pop off. Paint with high levels of hardener added is also going to suffer more from the effects any metal that has traces of oil when covered. Paint with hardener additions can also remain soft and mushy for extended periods until the cure is complete. This is not terrible but your paint efforts can be destroyed if pieces are rubbed together while still soft.

I hope you find this useful,
Solo

[Gizmo]

Good Stuff - Thanks Solo...

[Smokeone]

Man that is a great post Solo!

Sent from my iPhone using Forum Runner

[Gizmo]

%#$@^%# DC!

I just noticed my "new" avatar - come on, you can do better than that!

[The Czar]

HOLY CRAP SOLO!!!!!!!!!!


Rick...I think you look fabulous darling....that EDNA from the Incredibles...

[Brewery]

Haha, Edna from the incredibles.... Good thinking

[DUAYNE B]

wow, that was good reading Solo, thanks for the thread, alot of typing went into that,,,,,,,

[SoloQue]

That turned into a brutal read! Well I basically gave y'all the new hire training on spraying and trouble shooting with some popsicle viscosity stuff thrown in for relevance. All the Bold and Underlines got lost in the cut and paste so now folks have to dig and sift a bit more than I planned. Anyway, thanks for the feedback. Bottom line, if you spray too heavy you're not gonna like the final results. Guess that could have been the condensed thread

[Gizmo]

No that's the Hadie from NCIS Los Angeles !

[PvilleComp]

Great read Solo - thanks for writing it up.

[Tom_Heath]

Fantastic read.

You really burst my bubble though, I love the orange peel look. So many times I have tried so hard to get it and failed.

[SoloQue]

So many times I have tried so hard to get it and failed.

I got a few co-workers that have it down pat. I'll gladly send them your way if needed for that special look on your next paint job

[morgansdad]

now THAT!!! is the kind of stuff that I am looking for . excellent reading and tech advise thank you !

[Frank_Cox]

You bet bro! Solo know's his stuff! It's what we are here for!