Wet Sanding Tips

[redvettemike]

i am about through with a '71 442 that I have restored. I do my own body work/paint. I am still learning (although I have been doing same for 4-5 years). I use duPont bc/cc products. I painted the car (less hood) recently and then waited several days before wet (color) sanding the car. The paint had had a chance to harden and it was a real chore to cut the orangepeel out of the paint. Two days ago I painted the oai hood. This time I waited about 15 hours before wet sanding. I was amazed at how easy it was to cut the orangepeel out (using 1000 grit followed by 1200 and 2000). The paint jobber say to wait some (1/2 day) on buffing and I am doing as he says. It is pretty warm here and that can affect how long you must wait before wet sanding. There are many different ways to paint/wetsand/buff/etc. I am advising a process that worked for me.

[csstrux]

Assuming I remember correctly, the shop I worked in would usually paint at the end of the day, and would cut and buff the next AM. That is what I have done in the past with no issues.

[Texascarnut]

Each paint system has different recommendations or requirements. There are even different requirements for seemingly similar paint systems from different paint manufacturers and within differing grades of their similar individual products. Temperature and humidity conditions always play a roll in application and ultimately the processes involved in mixing thinners, activators, retardants, and deglossers. Explicit observing of the requirements in the manufacturer's data sheets for a given paint product are just as important as the paint gun having the correct tip, painting pressure, and compressor capacity, i.e.; compressor CFM rating.

All BC/CC paints have a time window for properly applying the clear over the base and it must be observed or bad things will indeed take place. In the case of DuPont Premier Pro maximum time between Base and Clear should be no more than 30 minutes. If using DuPont Nason 15 to 30 minutes between base and clear depending upon atmospheric conditions and number of base coat applications before applying clear.

Orange peel is just one of the many possible issues that can occur from failure to observe the manufacturer's application procedures. Which is to say there should be no or little orange peel issues with BC/CC paint application.
Orange Peel



Also known as: poor flow, poor levelling, pebbling


Description
Uneven surface formation - much like that of the skin of an orange - which results from poor coalescence of atomized paint droplets. Paint droplets dry before they can flow out and level smoothly together.





Origin and Potential Causes:

• Improper gun adjustment and techniques. Too little air pressure, wide fan patterns or spraying at excessive gun distances causes droplets to become too dry during their travel time to the work surface and they remain as formed by gun nozzle.
• Extreme shop temperature. When air temperature is too high, droplets lose more solvent and dry out before they can flow and level properly.
• Improper dry. Gun fanning before paint droplets have a chance to flow together will cause orange peel.
• Improper flash or recoat time between coats. If first coats of enamel are allowed to become too dry, solvent in the paint droplets of following coats will be absorbed into the first coat before proper flow is achieved.
• Wrong thinner or reducer. Under-diluted paint or paint thinned with fast evaporating thinners or reducers causes the atomized droplets to become too dry before reaching the surface. Too high viscosity.
• Low shop temperature.
• Too little thinner or reducer.
• Materials not uniformly mixed. Many finishes are formulated with components that aid coalescence. If these are not properly mixed, orange peel will result.
• Substrate not sanded thoroughly

Prevention Techniques:

• Use proper gun adjustments, techniques, and air pressure.
• Schedule painting to avoid temperature and humidity extremes.
• Select the thinner or reducer that is suitable for existing conditions. The use of a slower evaporating thinner or reducer will overcome this.
• Allow sufficient flash and dry time. Do not dry by fanning.
• Allow proper drying time for undercoats and topcoats. Not too long or not too short.
• Reduce to recommended viscosity with proper thinner/reducer.
• Stir all pigmented undercoats and topcoats thoroughly.
• Prepare and sand substrate correctly.
• Follow recommendations on technical data sheets.

Remedy

• For mild cases, sand and polish using recommended materials and techniques.
• In extreme cases, sand down to smooth surface and refinish, using a slower evaporating thinner or reducer at the correct air pressure.

[gearheads78]

^^^ Thats about the worst exable of orange peel I have seen.... WOW!

That said I don't care how good of a painter someone is. You have to cut and buff to make paint slick.

[Texascarnut]

Originally Posted by gearheads78

^^^ Thats about the worst exable of orange peel I have seen.... WOW!

That said I don't care how good of a painter someone is. You have to cut and buff to make paint slick.

Yeah, I think DuPont techs out did themselves in creating an example of orange peel. I know guys that are good enough with BC/CC painting nothing but a light buffing was necessary, I ain't one of them. But every now and then accidents do happen and little or no buffing required.

It's truly all about the proper mixing for the atmospheric conditions, gun setup, and of course technique. The latter being where most of us amateurs are extremely lacking in developing proper skills. Once every now and then does not lend itself to developing great skills.

[redvettemike]

Originally Posted by gearheads78

^^^ Thats about the worst exable of orange peel I have seen.... WOW!

That said I don't care how good of a painter someone is. You have to cut and buff to make paint slick.

In my limited experience, that is what I am seeing. The paint on this oLds flowed out pretty good. It still needed some cut/buff. I appreciate the facts given by txcarnut.

[BLUE72RAGTOP]

I'm an auto damage adjuster and one of our guaranteed repair shops is a dupont shop. They sand and buff every job, usually the same day with excellent results. They like to do this while the finish is still soft. They've got it down to a fine art, but they basically agree with redvettemike.

[ent72olds]

Originally Posted by Texascarnut

....

All BC/CC paints have a time window for properly applying the clear over the base and it must be observed or bad things will indeed take place.

Not all....Spies Hecker has an unlimited(infinite) window, which also makes it a good candidate for custom paint work.....and it is in writing!.......but, everything else you mention is dead on and very valuable info.

[Texascarnut]

Originally Posted by redvettemike

In my limited experience, that is what I am seeing. The paint on this oLds flowed out pretty good. It still needed some cut/buff. I appreciate the facts given by txcarnut.

Mike, hope you didn't think I was "picking" on you. Sometimes I have the finesse of an ill tempered alligator though not intending to come across that way.

Around these parts this time of the year it's a real bear to get paint mixed right because both the temperature and humidity can change in a heart beat. Just the temperature alone can drive one nuts, generally best to plan on shooting paint either between 11:00 am and 2:00 PM or waiting until 7:00 PM and plan on being finished by 10:00 PM. Typically too darn hot between those periods to control the mix to the point problems can be avoided. Too early and humidity is a problem and nasty things will happen.

[ent72olds]

Oh, and the biggest drawback to wet sanding and buffing a urethane clearcoat too soon is a few days after you think your done, it will finish curing(because by sanding and buffing, you opened up the surface and released the remaining solvent), and it will lose it's shine and you will notice the sanding marks again in the clear. Of course, another buff will remedy the issue. And that goes with all clearcoats all brands if not fully cured before buff....

[442_Mustang]

Another way to get a nice finish is to wet sand with 800 grit and reclear. Yes it's a bit more hassle but the paint should come out much cleaner. Every coat you spray will pick up imperfections and orange peel and the idea of reclearing is you should have only 2 or 3 coats on top of a perfectly flat surface. The shrinking should not happen. Also, it gives the paint much more depth. I'm going to spray my car tomorrow morning and I'm going with black single stage. Some evening next week I hope to wetsand with 800 and reclear. It really makes it look nice

[ijasond]

it's always best to follow the manufacturer's recommendations. Most clearcoats can be buffed in as little as about 4 hours, especially in the summer heat. Some of the new clears we use can be buffed in as little as 30 minutes. There are up and down sides to doing it soon after painting or waiting for it to cure. If you do it shortly after painting, your sand scratches will level out much quicker & with less effort. You can also get away with using a slightly courser sandpaper. The downside is, buffing this soon makes it much easier to burn the paint with the buffer. I've also sanded & buffed cars a month or more after painting. If you wait this long you might want to step up to a 2500 grit paper as the scratches will be more difficult to remove. I prefer to sand & buff after the paint has had time to cure(I usually wait at least a couple of days). On customer's cars we often have to buff the same day to get the car out, but on my stuff I take my time. I have a lot of experience & sanding/buffing and it is still a pain in the neck. For someone with limited experience, my best advice would be to take your time & have someone who doesn't mind answering a bunch of questions. Patience, patience.
I can make a beautiful paint job with a crappy gallon of clear, but having crappy buffing compounds & pads can make life way more difficult than necessary. I love the Meguiar's products and prefer them far more than the 3M stuff that costs 4 times as much. I use Meguiar's Diamond Cut compound, followed by their Dual Action Cleaner/Polish followed by a good sealant. Wax can be used if the paint is cured, but if your paint is not fully cured, wax can stop the curing process & your new paint job will self-destruct. I use a sealant called Vitreo which I also use in place of wax for all my other cars now. I also prefer the foam pads, some people still prefer the wool. Foam is the newer technology, but if you've used wool for a long time, it can be a tough transition. It's just a matter of preference.
The diamond cut compound will easily remove 2000 grit scratches, but can remove 1500 scratches(with a bit more time & effort).
When buffing, also follow the manufacturer's recommendations. Most compounds are best used at or around 1200-1500 rpms, slightly higher on the finer compounds. The slower your buffer turns, the deeper the cut. Start slow and speed up as you go to reduce swirling. This applies to any abrasive compound. You need to move the buffer back and forth slow enough to generate the heat needed to soften the paint, but not so slow that you melt it(which is pretty easy to do on new paint) I finish the job with the sealant on an orbital buffer and by hand with microfiber towels. You'll probably have to go back over things a few times, just be patient, it takes a long time to do it right.
I started painting when I was 16 woking after school in my dad's shops. I've worked as a detailer/floor sweeper, I've worked as a prepper, a painter, a body man, I've traveled around training painters and shop managers and I've owned my own shop for 5 years now. When I do a big job, like the restoration I'm trying to finish on my 66 Delta, I try to tackle every task without hesitation. But when it comes time to sand & buff, I procrastinate. I like to start & project and finish it asap, but buffing takes time and is tedious as well as boring. It drives me crazy. So good luck to you!

[redvettemike]

This is a followup to this post that I posted some months ago. As regards wet sanding we are using a d/a with a soft foam interface pad to wet sand the newly painted car. We start with 800 grit wet/dry paper and wet sand. We move onto 1500 and then to 3000 paper before compound/swirlmark buff (with foam). You have to be real careful around all edges but this works for us. The resulting finish is exceptionally slick with much less effort than hand sanding. Prob not for all but this is working for us.