Mechanics of masking

July 29, 2014
This seemingly simple area of paint and refinish takes time, skill and know how.

Automotive refinishing masking is a job that appears deceptively simple. It is one of the job duties with which many entry-level workers start in the paint department, but it is not as simple as it appears. On the surface, you are covering the areas of the vehicle that will not be painted and opening the areas that will receive refinishing. Simple, right? Except that since each paint job is significantly different from the previous, a detailed plan must be made every time. With masking, you must be thorough, pay great attention to detail and work fast. The better the mask job, the cleaner the finished product will be. Another challenge is the vast array of masking materials to choose from, each with its own specific task. Finally, I have never stopped from being amazed at the innovative ways that workers come up with to use old materials. So let's investigate the details of this large and varied job.

Inspection
Masking starts with the vehicle inspection. As part of the paint department, you may not see quality control as your primary job. But before the department starts work on a new job, those involved should read the work order and understand what the estimator has designated for this repair. Often, it is best to go over the work order with the shop foreman, allowing both of you to inspect the repairs, confirming that all work ordered has been done and completed to company standards. Starting a paint job only to find there is still work that must be completed will cost both time and profit.

A painter should check to see if the repair has gotten too close to the next panel, requiring it to be blended. Most painters believe that it takes at least 12 inches of blend room before the next panel. If there is less, for whatever reason, the next panel should also be blended.

Also, the inspection should check that the repair area is ready for paint. Is the repair flat and straight? Are all body lines correct? Do all the newly installed parts fit properly? Has the vehicle been de-trimmed as needed?

Check that the non-repaired panels to be blended are free of dirt, debris, chips and scratches. If there are defects in a non-repaired area, it may be necessary to call the customer and offer the opportunity to repair them before the blend.

The obvious question is, "Are all vehicles blended?” This is hotly debated, with managers and painters alike having strong opinions. There are those who say "blend it and send it." In other words, yes, all vehicles will be blended. They believe that today's very complex paint colors with metallics, multi-stages and pearls make it nearly impossible to match a panel’s paint colors without blending. Others believe that some colors can and should be panel painted, which saves time and material. This is a decision that you as a painter must make; but, many shops believe that all vehicles should be blended, as it makes more money and has less repaints in the long run.

Remove parts vs. mask
Though most of the trim removal is often done in the body shop, it still may be necessary for the painter to take some things off and properly store them. If new areas are added to the paint work order, trim may often be taken off. So when do you take trim off, and when do you mask? It may be best to mask a part when it can be masked properly (that is to say, with no signs of over-taping (getting tape on areas that should not be taped) or under-taping (not having tape covering the areas that should be taped). However, if the part can be taken off in less time than it takes to mask it off, it should be removed. Most vehicles today have molding and parts that fit so close to the car’s surface that masking is often impractical, and most, if not all, of the trim parts need to be taken off.

When a part is removed, it must be bagged and tagged. It is also best to store each vehicle’s parts on a dedicated rack for ease of reinstallation.

Figure 1
Figure 2
Figure 3

Masking materials
The amount of materials used for masking is so large that I am bound to miss something, so I apologize ahead of time if I overlook one you prefer!

Tape. In the past, there was only beige automotive masking tape. It came in 2”, ¾”, ¼”, and 1/8” widths. We used these for all taping on the vehicle. It was better than the tape from hardware store because it would lift off the vehicle and wouldn't leave a residue. Now we have many more sorts of tape to choose from. We still have beige tape and most people use it in the paper machine. We have blue or green tape that goes directly on the vehicle; it is thinner than the beige, but not affected by water or heat from the baking process. There is also have blue plastic tape, which can be stretched around tight corners for covering those hard-to-reach areas. There is also lift tape, which has a hard edge that is placed under objects and then pulled tight, lifting moldings up a bit so paint can migrate underneath and not leave a hard line.

Paper. We now have a vast selection of paper types and widths to choose from: some very thick and protective, others with a special film to prevent color or clear from bleeding, and still others like the general masking paper commonly used for nearly all masking jobs. Masking paper comes in a variety of sizes including 6, 12, 18 and 36 inches. Masking machines also come in different varieties. One of the more popular ones is called the tree, and it dispenses three or four sizes of paper. The machine dispenses both paper and tape together; the tape is half on the paper and the other half off, so it can be applied with ease to the vehicle.

Liquid mask.  Though not all shops use this, it is gaining popularity. It is a liquid that is sprayed on the area to be protected (Fig 1) and allowed to dry. When the painting is completed, it is washed off.

Aperture tape. This soft foam tape that has an adhesive on one side is used to fill body openings such as between the fender and door.

Plastic covers (bagging). Some painters will apply a 12-inch masking paper to the vehicle close to the painted area, and then cover the remainder of the vehicle with special plastic film (Fig 2). Others do not use any masking paper and use the bagging film completely, only opening the area to be painted.

Masking
Several masking techniques below should be mastered and then used as the situation requires.   

Back masking In this technique, wide tape such as 11/2- or 2-inch is placed halfway, and paper is applied to the tape that is sticking up. Alternately, in some cases, bagging film is stuck to the exposed tape, protecting the opening (Fig 3).

Figure 4
Figure 5
Figure 6
Figure 7
Figure 8

Reverse masking is done by placing masking paper on in the opposite direction, then folding it backward, causing a slight roll in the paper edge to avoid a "hard line" (Fig 4), which occurs paint when covers the masking, leaving a hard, raised area (Fig 5).  

Masking for blending. When masking for a blend is selected, the area that is left open is the area that will receive the base coat (Fig 6). The area that will be clear coated, in this case the roof and complete 1/4 panel, are also left open. After the base coat is applied to the repaired area (Fig 7) and allowed to dry, the entire open area is cleaned, and then clearcoat is applied (Fig 8).

Masking removal. There are two schools of thought regarding the removal of the masking. The first is that it should be removed as soon as possible after it is cured, which is good advice. The second theory is that the masking should not be removed until the vehicle has been detailed so the cleanup will be faster. The wise choice would depend on how much detailing is required. Removal of polishing compound can be difficult, but you do not want the masking paper to remain on the vehicle for an extended period of time. If only light detailing is required, the paper should be removed quickly; but if considerable polishing will be needed, leaving the masking paper on will help reduce the cleanup process.

As we have discovered, masking is no simple job. To do it properly and efficiently takes considerable practice and decision-making skill. The reason that many new workers are put on as painters’ helpers may be to see how much potential they have to become a painter. If you can master the complex skill of masking rapidly and completely, you may have a successful future in the paint shop.

Subscribe to ABRN and receive articles like this every month…absolutely free. Click here

Sponsored Recommendations

Best Body Shop and the 360-Degree-Concept

Spanesi ‘360-Degree-Concept’ Enables Kansas Body Shop to Complete High-Quality Repairs

ADAS Applications: What They Are & What They Do

Learn how ADAS utilizes sensors such as radar, sonar, lidar and cameras to perceive the world around the vehicle, and either provide critical information to the driver or take...

Banking on Bigger Profits with a Heavy-Duty Truck Paint Booth

The addition of a heavy-duty paint booth for oversized trucks & vehicles can open the door to new or expanded service opportunities.

Boosting Your Shop's Bottom Line with an Extended Height Paint Booths

Discover how the investment in an extended-height paint booth is a game-changer for most collision shops with this Free Guide.