under humid conditions. Mineral spirits or acid washes should definitely not be used at this stage. 2.  Etch the surface with a mild phosphoric acid wash. Etching increases paint adhesion and helps  overcome  the  stress  forces  generated  by expansion and contraction of the galvanized coating. After acid washing the surface, rinse it with clean water and allow to dry. When using acid, remember the situation can represent ac- tual or potential danger to yourself and other employees in the area. Continuous and auto- matic precautionary measures minimize safety problems  and  improve  both  efficiency  and morale of the crew. 3.   Apply a specially formulated primer. Two basic types of primer are in common use: zinc-bound and cementitious-resin. The zinc-bound type is used for normal exposure. Most types of finish can  be  used  over  this  type  of  primer.  Latex emulsion paints provide a satisfactory finish. Oil-based products should not be used over ce- mentitious-resin primers. A minimum of two coats  of  finish  is  recommended  over  each  type of  primer. CONCRETE AND MASONRY In Navy construction, concrete and masonry are normally not painted unless painting is required for damp-proofing.  Cleaning  concrete  and  masonry involves  the  removal  of  dirt,  mildew,  and  efflo- rescence  (a  white,  powdery  crystalline  deposit  that often  forms  on  concrete  and  masonry  surfaces). Dirt and Fungus Dirt and fungus are removed by washing with a solution of trisodium phosphate. The strength of the solution may vary from 2 to 8 ounces per gallon of water, depending upon the amount of dirt or mildew on the surface. Immediately after washing, rinse off all the trisodium phosphate with clear water. If using oil paint, allow the surface to dry thoroughly before painting. Efflorescence For  efflorescence,  first  remove  as  much  of  the deposit as possible by dry brushing with a wire brush or a stiff fiber brush. Next, wet the surface thoroughly with clear water; then, scrub with a stiff brush dipped in a 5-percent solution (by weight) of muriatic acid. Allow the acid solution to remain on the surface about 3 minutes before scrubbing, but rinse thoroughly with clear  water  immediately  after  scrubbing.  Work  on small areas not larger than 4 square feet. Wear rubber gloves,  a  rubber  apron,  and  goggles  when  mixing  and applying the acid solution. In mixing the acid, always add acid to water. Do not add water to acid; this can cause the mixture to explode.  For a very heavy deposit,  the  acid  solution  may  be  increased  to  10 percent and allowed to remain on the surface for 5 minutes  before  it  is  scrubbed. Repairing  Defects All  defects  in  a  concrete  or  masonry  surface  must be repaired before painting. To repair a large crack, cut the crack out to an inverted-V shape and plug it with grout (a mixture of two or three parts of mortar sand,  one  part  of  portland  cement,  and  enough  water to make it putty-like in consistency). After the grout sets, damp cure it by keeping it wet for 48 hours. If oil paint  is  to  be  used,  allow  at  least  90  days  for weathering  before  painting  over  a  grout-filled  crack. PLASTER AND WALLBOARD Whenever possible, allow new plaster to age at least 30 days before painting if oil-based paint is being applied. Latex paint can be applied after 48 hours, although  a  30-day  wait  is  generally  recommended. Before  painting,  fill  all  holes  and  cracks  with spackling compound or patching plaster. Cut out the material  along  the  crack  or  hole  in  an  inverted-V shape. To avoid excessive absorption of water from the patching material, wet the edges and bottom of the crack or hole before applying the material. Fill the opening to within 1/4 inch of the surface and allow the material to set partially before bringing the level up flush  with  the  surface.  After  the  material  has thoroughly set (depending on the type of filler used), use  fine  sandpaper  to  smooth  out  the  rough  spots. Plaster and wallboard should have a sealer or a prime coat applied before painting. When working with old work, remove all loose or scaling paint, sand lightly, and wash off all dirt, oil, and stains. Allow the surface to dry thoroughly before applying the new finish coat. WOOD Before being painted, a wood surface should be closely inspected for loose boards, defective lumber, protruding nail heads, and other defects or irregularities. Loose  boards  should  be  nailed  tight,  defective  lumber should be replaced, and all nail heads should be counter- sunk. A  dirty  wood  surface by sweeping, dusting, and soap and water. In washing 8-5 is  cleaned  for  painting washing with solvent or wood, take care to avoid