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allow the top surface of the coating to dry, trapping the solvents underneath. If another heavy coat is applied before the first one dries, wrinkles may result. It may also have the effect of lifting the coating underneath, almost with the same result as a paint stripper. 

Rapid changes in ambient temperatures while spraying may cause an uneven release of the solvents, causing the surface to dry, shrink, and wrinkle. Making the mistake of using an incompatible thinner, or reducer, when mixing the coating materials may cause not only wrinkles but other problems as well. Wrinkled paint must be completely removed and the surface refinished. 

## Spray Dust 

Spray dust is caused by the atomized spray particles from the gun becoming dry before reaching the surface being painted, thus failing to flow into a continuous film. [Figure 8-21] This may be caused by: 

• Incorrect spray gun setting of air pressure, paint flow, or spray pattern. 

• Spray gun being held too far from the surface. 

• Material being improperly thinned or the wrong reducers being used with the finish coats. 

The affected area needs to be sanded and recoated. 

## Painting Trim and Identification Marks 

## Masking and Applying the Trim 

At this point in the project, the entire aircraft has been painted with the base color and all the masking paper and tape carefully removed. Refer again to the coating manufacturer’s 

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technical data sheet for “dry and recoat” times for the appropriate temperatures and “dry to tape” time that must elapse before safe application and removal of tape on new paint without it lifting. 

## Masking Materials 

When masking for the trim lines, use 3M$^{®}$ Fine Line tape. It is solvent proof, available in widths of 1 ⁄ 8 –1 inch and, when applied properly, produces a sharp edge paint line. A good quality masking tape should be used with masking paper to cover all areas not being trimmed to ensure the paper does not lift and allow overspray on the basecoat. Do not use newspaper to mask the work as paint penetrates newspaper. Using actual masking paper is more efficient, especially if with a masking paper/tape dispenser as part of the finishing equipment. 

## Masking for the Trim 

After the base color has dried and cured for the recommended time shown in the manufacturer’s technical data sheet, the next step is to mask for the trim. The trim design can be simple, with one or two color stripes running along the fuselage, or it can be an elaborate scheme covering the entire aircraft. Whichever is chosen, the basic masking steps are the same. 

If unsure of a design, there are numerous websites that provide the information and software to do a professional job. If electing to design a personalized paint scheme, the proposed design should be portrayed on a silhouette drawing of the aircraft as close to scale as possible. It is much easier to change a drawing than to remask the aircraft. 

Start by identifying a point on the aircraft from which to initiate the trim lines using the Fine Line tape. If the lines are straight and/or have large radius curves, use ¾-inch or one-inch tape and keep it pulled tight. The wider tape is much easier to control when masking a straight line. Smaller radius curves may require ½-inch or even ¼-inch tape. Try and use the widest tape that lays flat and allows for a smooth curve. Use a small roller (like those used for wallpaper seams) to go back over and roll the tape edges firmly onto the surface to ensure they are flat. 

Finish masking the trim lines on one side of the aircraft, to include the fuselage, vertical fin and rudder, the engine nacelles and wing(s). Once complete, examine the lines. If adjustments are needed to the placement or design, now is the time to correct it. With one side of the aircraft complete, the entire design and placement can be transferred to the opposite side. 

Different methods can be employed to transfer the placement of the trim lines from one side of the aircraft to the other. 

