Painting a car using two stage system with HVLP paint gun

by David Lavalley on March 15, 2013

Paint finishedIn a previous article, I showed you the basic technique of doing body work. As promised, I will now show you how to finish the job using a two stage paint system sprayed on with a HVLP gun. A special thanks to my father who spent many years in the auto paint industry and assisted me with the writing of this article.

What’s the difference between single stage and two stage paint?

There are basically 2 different ways that you can paint a car. The single stage or the two stage method. Both methods can yield great results. The single stage paint technique was the only way you could paint a car prior to the 1980′s when 2 stage was introduced. With the single stage, the clear coat and base coat are mixed together and sprayed on with multiple coats. The end result often yields surface imperfections that needed to be buffed out.

Two stage paint was introduced in the 1980′s and is still popular today. The idea is to first spray what is called a base coat followed by a clear coat. The clear is spayed directly on top of the base coat almost immediately after the base is sprayed. This technique generally results in a better over all finish. One disadvantage of using a 2 stage is that the clear will eventually peel off and also if you buff too much in one area, you will burn through to the base coat.

Two stage painting – How to

Equipment and supplies required

First, you must gather the proper supplies in order to get the job done. There are a few tools that one must have access to before getting started.

  • HVLP paint gun. HLVP or High-volume, low-pressure gun can be purchased from a number of retailers including Lowe’s, Harbor Freight, or Grainger. Choose one that has a hopper size large enough for the job that you are interested in doing. If you are only painting a small panel such as a door or fender, pick one with an 8 oz or so hopper. Also, check out any available reviews before making a purchase. Some guns are poorly constructed and should be avoided. 
  • Air compressor with hose. This is also another necessity. If you already have an air compressor, ensure that it is large enough to get the job done without running out of pressure or overworking the compressor. The packaging should give you an idea of the types of jobs that it can handle. For instance, a 1 gallon compressor will likely not get the job done.
  • Face mask. Many of the chemicals used are toxic and can cause respiratory problems among other issues. When doing large jobs especially, pick up a respirator that is rated for use with chemicals.

With these three necessities, you are going to need some chemicals and other supplies. Most of these can be picked up from your local paint supplier or even car-quest. Ensure that all the chemicals that you choose are compatible with each other.

  • Paint base coat. If your vehicle is painted the original paint color, there are a couple ways that you can identify the color of the paint. The first is the VIN number located on the dashboard near the drives side. Call the dealership with this number and they can give you the paint code. The other way is to locate the information plate on your vehicle. This plate contains all types of information about your car – paint color, trim type, and other feature. This plate can be located in the door jam, under the hood, inside glove box or even in the trunk. Once you located it, have your local paint store mix a batch up for you. For a small job, a half pint to one pint will do.
  • Reducer. Your paint will be too thick to spray through a paint gun. For this reason, you must thin it out. Since these paints are oil based, mixing with water will not work. You will need a reducer which acts like a thinner, giving you the needed consistency for spraying. Once again, ensure that you choose a product that is comparable with your paint.
  • Clear coat. This is the stuff that makes your car shine and is used during the second stage of painting. Clear coat is simply a semi flexible product that causes the paint to shine and protects it from the elements for many years to come. There are several manufacturers who produce this product. Only a few ounces are required for a small job.
  • Activator. Necessary to activate the clear coat. This product acts as a harder, causing the clear coat to quickly dry to a hard shell. For a small job you will only need a few ounces. Pick an activator that will work in the desired painting temperature range.
  • Prep-sol. This product is used to assist with the removal of surface contaminates prior to paining. It is necessary and ensures that the paint properly sticks to the surface.
  • Lacquer thinner. This is used to clean your spray gun after being used. It is extremely effective at removing fresh paint and clear coat. It will even work on dried paint. Do not use this product under any circumstances near or around where you are about to paint.
  • Lint free paper towels. Before painting, the surface needs to be cleaned of all contaminates, including dust. Standard paper towels are not up for the job. A good quality towel that does not leave lint behind on the surface is a must. Scott’s shop towels are a good choice.
  • Masking tape.  A quality masking tape is a must when painting. Cheap tape can be hard to work with and difficult to remove from surfaces once you are finished. 3M makes some really great products when it comes to painting. These tapes leave a nice clean edge, which is what you want when masking off areas that you don’t want paint on.
  • Masking paper or newspaper.  You will want to mask the area around where you are working with masking paper or newspaper. If you do not paint much, newspaper will do the trick.
  • Miscellaneous.  Paper or plastic cups to mix paint, stir sticks, strainers. Most paint stores will give you these products free of charge.

Choosing a paint location and day

Having a paint booth is not necessary when painting a small panel or in some cases an entire car. I have seen some really great outdoor jobs that are difficult to differentiate from a paint booth job. The key is to choose a good location and good weather. Pick a grassy area away from loose sand. Choose a sunny day, low humidity and low wind. The ideal painting temperature is between 50 degrees and 80 degrees F.

Surface preparation

Prepare area with prep-solOnce the surface to be painted has been sanded and all bare metal primed as described in the dent removal post, you will need to prepare the surface to for painting. First, mask off any surrounding areas that you do not want paint to get on. Use your masking tape and paper to mask off an area that is 1 to 2 feet from where you will be spraying. The more masking you do, the better, as over-spray is difficult to remove. Start by getting a clean edge with 3/4″ tape and then lay your paper down and tape this to the masking tape. The work area needs to be wiped down prior to painting. This step should take place right before you pick up the paint gun and lay the first coat. Use Prep-sol and a lint free paper towel to wipe down the work area. On a moderately warm day, this should evaporate almost instantly.

Apply the base coat

2 stage chromat paint adding full base nason reducer to paint Pour paint into hopper with strainerspraying base coat on doorFor a small panel, you should start by mixing 4 oz or so of paint up. Create a 50/50 mixture of paint and reducer. The reducer will thin out the paint so that it will easily flow from the gun to your panel. This may take some experimenting depending on the technique that you develop and the  paint gun that you choose. Pour your mixed paint into the gun hopper. Use a funnel strainer with a fine mesh screen when pouring just in case there are large contaminates in your paint such as dried bits of paint. In the mean time, fire up your air compressor and allow it to fully charge. Pull the drain plug an allow any water in the tank to escape and then let it fill back up. Water in your air lines is not good and will result in a poor paint job.

Zero in your paint gun by turning the pressure regulator down to get it within the manufactures specifications. This can vary greatly depending on the spray gun that you are using. The pressure will likely be somewhere around 25 PSI for a HLVP gun. Before spraying any paint on the vehicle, wipe the surface down with a paper towel and prep-sol. Spray a bit of paint into the air and adjust your stream. To concentrated and you will get streaks and runs. Too wide, the paint will dry before it hits the surface and will not lay properly. Hold the paint gun approximately 1 foot from the panel and use a sweeping motion to apply. While doing this, pay close attention and ensure that you are slightly overlapping your spray lines. Too much overlap or not enough overlap and you will have wet or dry streaks. Apply several coats, waiting a couple minutes between coats. When finished, the entire panel should be one consistent color. It will not shine yet but don’t worry, this step is next.

Apply the clear coat

Pouring clear coat Adding activator to clear Mirror with clear coatThe clear coat is applied in the same manner. Once the base coat is applied, clean your gun out by pouring thinner in the hopper, cap it, give it a shake and force the thinner through the gun to clean out the inside components. Do this a couple times and you are ready to apply the clear coat. Ensure that all thinner has been cleared before proceeding.

As with the paint, you will need to mix the clear coat before applying. The clear uses an activator that allows it to harden quickly. Without it, your clear will remain tacky and never dry. When shopping for an activator, take the ambient temperature into consideration. There are three different types of activator that you can purchase – High, medium and low temperature. Since we are going to be painting above 55 degrees, the mid temperature activator will be sufficient.

Mix up 4 oz or so of the clear coat according to the manufactures instructions. Pour the clear into your hopper and adjust your spray once again as described above. You will want a nice wet layer but not too wet. Use a sweeping motion to apply the clear coat while paying close attention to the wet edge. Look closely when applying to ensure that you are not putting it on too dry as this will result in a rough surface. Once the clear has been sprayed on, allow it to dry as you clean out your paint gun as described above.

Remove the masking tape and paper

Soon after painting you will want to remove the masking tape and paper. It is a good idea to do this just minutes after the clear coat has been laid. Carefully peal back the paper and tape at a 45 degree angle, being careful not to disturb the freshly laid paint. It is important to pay close attention as one slip at this point can ruin a good paint job.

Clean off any over spray immediately with prep-sol

Use a rag and prep-sol to clean off any residual over spray. Over spray is simply the paint and clear coat that has landed in areas other than where anticipated. If you catch the over spray early, a simple wipe will remove it. Old over spray will require a bit more elbow grease.

Sand and buff to a smooth finish

The fresh paint has been laid and a few days later you run your fingers across the panel and notice it has a bit of grit in it. This is simply dust and other organic material that has landed on your clear coat before it had a chance to dry. Give your paint a couple days to dry. Take a piece of 800 or 1000 sand paper and lightly wet sand it. Afterwards, hit the area with a rubbing compound and buffing wheel. Finish the job by applying a fresh coat of wax. Remember, since this is a two stage finish, if the contaminates are in the bottom base coat, buffing will do no good as it will remove the clear coat, leaving you with a dull unprotected finish. Only surface contaminates in the clear coat can be sanded and buffed out.

 

Before and After. Note, rear door dent was not removed. 

Dent is car door Paint finished

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