If the gun is not working properly, use the following  information to troubleshoot the problem:  As a general practice on any surface being painted, spray each  application of coating in a different direction to facilitate even  and complete coverage. After you apply the primer, apply  the tack coat and subsequent top coats in opposite directions,  one coat vertically and the next horizontally, as appropriate.  Blushing is the dull milky haze that appears in a paint finish.  [Figure 8-14]  It occurs when moisture is trapped in the paint.  Blushing forms when the solvents quickly evaporate from the  sprayed coating, causing a drop in temperature that is enough  to condense the water in the air. It usually forms when the  humidity is above 80 percent. Other causes include: •  A pulsating, or spitting, fan pattern may be caused by  a loose nozzle, clogged vent hole on the supply cup,  or the packing may be leaking around the needle. •  If the spray pattern is offset to one side or the other,  the air ports in the air cap or the ports in the horns may  be plugged. •  If the spray pattern is heavy on the top or the bottom,  rotate the air cap 180°. If the pattern reverses, the air  cap is the problem. If it stays the same, the fluid tip  or needle may be damaged. •  Other spray pattern problems may be a result of  improper air pressure, improper reducing of the  material, or wrong size spray nozzle.  •  Improper cleaning and preparation of the surface to  be finished. •  Application of the wrong primer. •  Incompatibility of the topcoat with the primer.  [Figure 8-13] •  Improper thinning of the coating material or selection  of the wrong grade reducer. •  Improper mixing of materials.  •  Contamination of the spray equipment and/or air  supply. Correction for poor adhesion requires a complete removal of  the finish, a determination and correction of the cause, and a  complete refinishing of the affected area. Poor Adhesion Sequence for Painting a Single-Engine or  Light Twin Airplane Blushing •  Incorrect temperature (below 60 °F or above 95 °F).  •  Incorrect reducer (fast drying) being used. •  Excessively high air pressure at the spray gun. Start by spraying all the corners and gaps between the control  surfaces and fixed surfaces. Paint the leading and trailing  edges of all surfaces. Spray the landing gear and wheel wells,  if applicable, and paint the bottom of the fuselage up the sides  to a horizontal break, such as a seam line. Paint the underside  of the horizontal stabilizer. Paint the vertical stabilizer and the  rudder, and then move to the top of the horizontal stabilizer.  Spray the top and sides of the fuselage down to the point  of the break from spraying the underside of the fuselage.  Then, spray the underside of the wings. Complete the job  by spraying the top of the wings. If blushing is noticed during painting, a slow-drying reducer  can sometimes be added to the paint mixture, and then the  area resprayed. If blushing is found after the finish has dried,  the area must be sanded down and repainted.  The biggest challenge is to control the overspray and keep the  paint line wet. The ideal scenario would be to have another  experienced painter with a second spray gun help with the  painting. It is much easier to keep the paint wet and the job  is completed in half the time.  Common problems that may occur during the painting  of almost any project but are particularly noticeable and  troublesome on the surfaces of an aircraft include poor  adhesion, blushing, pinholes, sags and/or runs, “orange peel,”  fisheyes, sanding scratches, wrinkling, and spray dust.  $^{ }$Common Paint Troubles Figure 8-13.  Example of poor adhesion.  8-13