Orange peel

Orange peel
Orange peel is a coating defect that occurs when the coating that emerges from the spray gun is not properly atomized. As a paint sprayer consultant, I usually give two predominant methods to eliminate orange peel:
Without changing the air atomizing pressure, DECREASE the flow of paint to the gun by turning the fluid control knob to the right, clockwise.
1 - Without changing the fluid flow to the gun, INCREASE the air pressure to the gun.
2 - With HVLP guns you are only allowed to increase the air pressure so that the pressure at the cap of the gun does not exceed 10 psig. There is a third method, namely to add some thinners (solvent) to the paint but as an environmental coating consultant, I never recommend this as it adds to air pollution.
Orange peel problem
Orange peel is a coating defect that occurs when the coating that emerges from the spray gun is not properly atomized.
CAUSE
A. Under reduction and/or air pressure too low.
B. Thinner/reducer evaporates too fast for spray conditions.
C. Excessive film thickness or piling on of heavy wet coats.
D. Improper spray gun set-up.
E. Improper painting technique.
REPAIR
1. Compound or polish to reduce surface texture.
2. Or, sand smooth with 1200 or finer grit sandpaper, compound and polish to restore gloss.
3. Or, sand smooth and refinish.
PREVENTION
A. Use proper reduction ratio and spray at recommended air pressure.
B. Select recommended thinner/reducer based on temperature, humidity, air movement, and size of repair.
C. Avoid heavy coats and excessive film thickness.
D. Use recommended spray gun, fluid tip and air cap for the material being sprayed. Always
adjust the gun for best atomization and balanced spray pattern before paint application.
E. During paint application, hold the gun perpendicular and parallel to the surface. Adjust speed of
pass, pattern overlap, and distance from the panel to achieve the desired appearance.
Orange peel measuring principle
Orange peel or texture of a painted surface is measured by scanning a light beam across the surface and receiving the reflected beam on an area detector generating a signal having a first component varying with surface slope variations in the painted surface and a second component due to scan rate. Apparatus is provided for orienting the light beam relative to the painted surface so as to be reflected there from to the detector area without re‐reflection from the painted surface;and a converging lens converges the light beam on the area detector. A portable, surface contacting embodiment uses a plurality of projecting feet for orientation to the painted surface and relies on the converging lens for convergence. In a non‐contact embodiment, variations in orientation and curvature of the surface are detected by the second component of the signal and compensated for in closed loop control of a mirror and the converging lens to dynamically converge the beam on the area detector.
Apparatus
A ‐wave‐scan dual
Company : BYK Gardner GmbH
Name : wave‐scan dual
Address : Lausitzer Straße 8
82538 Geretsried , Germany
info.BYK.Gardner@altana.com
www.byk.com
B-ROUGHNESS CHECKING
TAYLOR HOBSON LTD
PO Box 36,2 New Star Road,
Leicester, LE4 9JQ
ENGLAND
Tel: +44 (0) 116 246 3085
E-mail: sales@taylor-hobson.com