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 a. Some of the common causes of an orange peel finish are:
(1) Too high or too low air pressure on the spray gun.
(2) Paint viscosity too high or incorrect thinners used.
(3) Inadequate surface preparation.
(4) Holding the gun so close to the surface that air ripples result.
b. Another common defect in spraying is mist or fog. These defects are caused by the following:
(1) Over atomization caused by:
(a) Air pressure too high.
(b) Fluid pressure too low.
(c) Wrong air cap for material used.
(d) Wrong fluid tip for material used.
(2) Improper use of gun caused by:
(a) Incorrect stroking.
(b) Gun too far from surface
5-11. Paint Failures. The types of paint failures to look for when inspecting a surface before or after an
application of paint are described below.
a. Alligatoring or Checking. Alligatoring, or checking, exists when the outer layer of paint is broken and
underlying paint coats are visible, often presenting an appearance similar to alligator hide. This may be
caused by applying paint:
(1) To unseasoned wood.
(2) Over a relatively soft undercoat.
(3) Over previous coats before they have dried.
(4) Of a hard drying nonelastic type over a more elastic paint.
b. Cracking. Cracking exists when a break extends through to the painted surface. Paints, which lack
elasticity because of aging or other causes, can no longer contract or expand with moisture and
temperature changes and, therefore, crack.
c. Flaking, Scaling, and Peeling. Flaking, scaling, and peeling are characterized by the detachment of
pieces of paint, generally irregular in shape. When pieces are small, it is termed flaking; when pieces
average over 1/4 inch, it is termed scaling; when pieces are larger (over 1 inch), it is termed peeling.
Flaking and scaling usually follow cracking and have the same causes. Peeling is often caused by the
presence of moisture behind the film or by incompatibility of paint film.
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