Effective spray masking can save time in the paint booth

Jan. 1, 2020
Spray masking a vehicle is a highly individualized task and each vehicle requires a different technique, depending on what is being painted.

Masking – we do it every day for every car that we paint (Fig 1). We often give it little or no thought, commonly assigning the task to the most junior employee in the shop. If you were to give masking tasks to 100 different painters, the cars would be masked in 100 different ways.


It is a highly individual task; each worker has his or her own likes and dislikes, and each vehicle requires a different technique depending on what is being painted. One of the things I tell young technicians is that because each job is different, it keeps our work from feeling repetitive.

Each year as a college class is about to graduate, we invite technicians from local shops to judge our graduates on their ability to paint a project. One of the most difficult areas to judge is the masking. Ask any painter's helpers: it takes a while to learn exactly how any given painter wants a helper to mask a car. And though there are hundreds of techniques that will get the job done correctly, it is a task that continually needs refining.

Over the years, the industry has seen changes to materials and techniques for masking vehicles. Masking tape now comes in a staggering array of types and sizes. There's lift tape, aperture tape, fine line, plastic masking film for "bagging" and more. It seems as though every few months something new comes out that's available for painters or painters' helpers to try.

As with many other tasks in the paint shop, the faster one can complete a job increases the opportunity for profit. Masking with bagging (plastic film) has become very popular and is done in most shops. Unfortunately, unless care is taken, overspray can find its way under the masking film and cause a great deal of extra cleanup on the vehicle.

Shops also seem to be looking for the magic bullet that will eliminate dirt in the paint booth. Although there is no such thing as a perfectly clean paint job, we must continually look for ways of reducing dirt to as little as possible.

Also, we would like to find ways to reduce the amount of time it takes to detail a car and prepare it for delivery. If we can leave the masking paper on while we detail, cleanup is much faster; but driving a car out of the booth that still has masking paper or even plastic masking film on reduces the visibility; therefore, many painters remove it before moving the vehicle. This results in exposing glass and other areas of the car, which can become dirty from polishing compound.

Masking a vehicle can take as much as 20 percent of the paint time. If the vehicle is masked and bagged for priming, the masking is then removed to wash the vehicle, and finally re-masked for paint – a process often done to reduce the amount of dirt in the final paint. This procedure does reduce the amount of time necessary for cleanup and in the long run will pay for itself because of the decreased amount of dirt. Yet, it is still quite time consuming and costly.

Even with the best masking, overspray often finds its way under the paper and masking to areas where it should not be, causing more cleanup. Also, in vehicle areas that are very difficult to both clean and mask (such as wheel openings), dirt often finds its way from these areas to the paint job.

Liquid spray mask (Fig 2), which can be applied easily with even an old siphon feed spray gun, can help eliminate or at least reduce many of the problems mentioned above. Liquid mask has been around for some time, and despite its advantages, many shops have not used this product. It can protect vehicles while in the shop as an overspray masking, which can be left on during cleanup. It can be sprayed in areas such as wheel wells, which can be easily washed off while the vehicle is being cleaned for delivery. Overspraying, compound contaminants and even just typical shop dirt that can fall onto the vehicle during the repair process can be washed off with a hose and water.

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Vehicle protection

One of the advantages to spray masking, especially for vehicles that may be in the shop for a long period of time like the restoration vehicle shown (Fig 3), is that it can be applied to a vehicle when it first arrives and left on for the duration of its time in the shop, protecting it from overspray, dust and other contaminants.

Some shops will apply spray mask to a vehicle in the areas that will not be worked on to protect it. It can be removed during washing.

Reduced masking time

The manufacturers of spray masks claim that more than 20 million vehicles have been protected with liquid mask since its inception. They also claim it can be applied within three minutes, with a rapid dry time (15 to 25 minutes); and that like waterborne paint, its dry time can be decreased by using a fan or air amplifiers (Fig 4), thus cutting costs by 60 percent.

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Liquid mask is applied with a conventional spray gun with a large needle-nozzle setup (we used a 2.0). The spray mask is applied within 8 inches of the areas to be painted (Fig 5). Then 12 inches of (Fig 6) masking paper is applied to the edge, which overlaps the spray mask area. A minimal amount of time and paper is used to complete the masking procedure.

Liquid mask can be sprayed on the inside of the wheel opening prior to masking with paper, thus reducing dirt that may remain and find its way into the paint job. The liquid mask can be left in place during detailing and thus any compound that finds its way onto the vehicle can be easily washed off during detailing. When the vehicle is ready for detailing, the paper is stripped and the vehicle is rinsed with water and left to stand for few minutes. The normal soap and water washing removes the liquid mask, overspray, dirt and other contaminants on the car.

Liquid mask and your booth

For years we have looked for ways to keep the walls and floors of our booths and prep decks clean and reduce the amount of dirt that eventually finds its way into the paint job (Fig 7). Even in the best of conditions, however, overspray finds its way onto the walls. Although various floor coverings have been used, a perfect solution has not been found. Liquid mask booth that I used in the past has been a clear covering, similar to the liquid mask applied to vehicles, and thus did not help provide the clean white reflective surface needed in a spray booth without considerable work and repainting prior to application.

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So we greeted the introduction of a white liquid mask for booths with great interest. The product will withstand up to 500 bake cycles and can be applied over a surface that may have overspray and various colors adhering to the wall. To try it out, we gave the booth, walls and floor a thorough cleaning (Fig 8), which removed a significant amount of overspray and dirt but did not clean the walls completely (Fig 9).

We then masked off the windows and lights (Fig 10) and applied two coats of white booth mask (Fig 11). To avoid getting the white booth wall liquid mask on the floor, a large piece of cardboard was laid down and moved as the application progressed, which reduced the amount of time necessary for masking (Fig 12). All the glass was thoroughly cleaned, and a clear sprayable covering was applied over all the glass to protect it from overspray.

After the walls were completely coated, a water-based particle control was applied directly to the concrete floor. This coating attracts dirt particles and overspray down to the floor and thus does not circulate while the vehicle is being painted. The manufacturer claims that in testing, it reduces airborne dirt by 60 percent.

For years we have been covering the floors with rosin paper, which requires periodic replacement that can be time-consuming. So far, applying particle controller directly to our concrete floor (Fig 13) has proven to be very useful. The floor swept easier and cleaned up quickly, and it appears to be reducing the amount of dirt in the air and thus on the paint job.

We applied two coats of white booth mask, which covered the wall well (Fig 14). While the application of a third coat would have likely covered any overspray that was on the wall, the finished product was a clean, highly reflective and pleasant paint booth to work in.

Dirt was markedly reduced and color match was more easily recognized with the increased lighting from the clean, white walls. According to the instructions, spray booth liquid masks do not have to be completely washed and stripped off. When it becomes necessary to reapply, we can simply have additional spray mask applied over the old masking to freshen up the walls.

Sprayable liquid mask has many advantages: the reduction of application time, reduced cost per vehicle, cleaner and easier-to-maintain spray booths and cleaner paint jobs with less detailing time. It seems as if the benefits of liquid mask for both vehicle masking and booth maintenance have been largely overlooked. Since no new equipment is necessary for its application, (and in fact its application to booth walls and floors take no longer than is normally done for booth maintenance), and it results in a cleaner working environment and cleaner paint jobs, its use in the shop may warrant a trial.