Spray Gun Air

Spray Guns And Spraying For Lacquer

Dirt is the biggest bugbear of spraying. Nozzles, tubes and liquids should be spotless; soak the parts in thinners and strain your lacquers through a single thickness of nylon stocking. Having carefully prepared your surface, damp all dust and sweep up thoroughly, then disturb it no more.

Practise spraying on a large piece of flat panel until you have a flat fan of spray, which will coat an area 35-45cm (15-18in.) wide with the gun held 20-30cm (8-12in.) from the surface at 90° to it. It is easier to spray a vertical surface than a horizontal one. Wait a minute to see the effect on your test surface, because lacquer takes some time to run if it is going to. Thin it 10 per cent and get the right consistency by timing it through a viscosity cup. The liquid should flow in a continuous stream off the end of a stick held at 45°.

Spraying techniques are illustrated opposite. Never trigger or stop the gun while it is pointing at the surface. Start the spray, and stop it, off the panel at the beginning and end of your strokes. Do internal corners in one smooth movement; external corners should have one stroke each side and one at a 45° angle.

Pre-catalysed lacquers can be de-nibbed with 600 grit wet and dry paper and water, wiped and tack-ragged after 45-60 minutes, and are then ready for recoating. Acid-catalysed lacquers take longer, about three hours on average. Final coats should be steel wool and waxed, or rubbed with burnishing cream.

Damp in the air causes a milky bloom as the lacquer dries. Burnish it with abrasive cream or paste, or if that does not work strip and refinish. Spray will pick up moisture in a cold damp atmosphere and take it to the surface, where it mixes with the lacquer, causing pits and craters in the finish, with the same white bloom. The air must be dry and warm, but if it is too hot it will dry the lacquer too quickly.

Always clean the gun as if it was a surgical instru¬ment. Dismantle it, soak all the parts in thinners and blow thinners through the gun until there is not a trace of lacquer in the spray.

Finally, take elaborate safety precautions. Fine spray vapours are highly volatile, and extremely unpleasant to inhale; always wear a face mask, have a good extraction system, or do the work outside. Just having the windows open is not nearly enough.

About the Author

Also learn how to drive your car in the rain and how to dress during spring. Dress represents your personality.

FUSION Air Purge spray gun from GRACO