Painting Hardboard / Masonite / Pressed Wood

Hardboard-Masonite/Pressed Wood. Made from chipped wood and reconstituted with resin (adhesive) under pressure. Available in interior and exterior grades with or without factory primer applied. Used extensively on exterior applications painted with a factory applied primer coat. ( Factory applied primers are intended for short term protection of the material while in transit and prior installation. They should not be considered a full prime coat prior to the application of field applied finishes.) Production materials and fabricating methods vary according to manufacturer and geographical locations of plant. Most West Coasts raw materials are composed of redwood and cedar (back of board dark brown) where Southern and Eastern varieties utilize yellow pine (light to medium gray). Each manufacture offers their own painting specifications, but the following will provide acceptable recommendations.

1.  NOT FACTORY PRIMED. This is seldom encountered for exterior work. Requires prompt protection with a full coat of oil/alkyd primer or a full coat of stain blocking latex primer. Finish with two coats of latex or oil type finish coat. On interior use, hardboard should be treated as unfinished wood. Some coarse “chipboards” require a filler coat if a completely smooth surface is desired.

2.  FACTORY PRIMED. Effective way of protecting the face and lap board siding during transit and during installation. All hardboard manufactures stress that pre-primed hard board must be finished before 90-120 day after exterior exposure. If finishing is delayed beyond that period, treat the exterior siding as though it were unprimed (i.e. requires an exterior primer and two finish coats). Failure to follow these precautions can cause premature delaminating (peeling) of the finish coat from the primer. Directions for application of siding (as listed on packages) should be followed, paying particular attention to vapor barrier instructions. Hardboard should be protected from the weather, as any water may cause stains that reappear after finish has been applied.


Painting Plastics

Painting plastics can be simple and successful or it can be complex and a disaster. The reason for this is that “plastics” include a wide number of organic resin formulations and a wide range of processing methods. On molded products, mold release items (silicone’s, waxes and surface active agents) can cause adhesion problems. Some mold release items are paintable, but others will keep the coating from adhering. The best advice: follow the directions for painting the specific product from the manufacture. Often the plastic has a factory applied primer or finish coat. This simplifies the problem, as you are now painting paint and not the plastic, so proceed with normal good painting practice, either interior or exterior.

  If the manufacture advice in not available and the object has not been factory primed-what next? Oil, powder, dust or almost any contaminate can adversely affect adhesion of paint. Paint adheres better to roughened surfaces than smooth surfaces. Certain proprietary primers are touted for good adhesion to plastics. An acceptable procedure would be:

1. Wipe the surface with a cleaning solvent. The cleaner must be compatible with the plastic, as the wrong solvent can be damaging. Sometimes scrubbing with soap and water is an alternative. Try a sample in a inconspicuous location and observe results. (Avoid solvents that cause crazing, cracking or dissolve the plastic).

2.  Sanding with “wet or dry” abrasive does a good job of removing the gloss or roughing dense surfaces. This often removes “mold release agents” and gives paint a chance to adhere. This can be done in conjunction with detergent or solvent. Rinse well after sanding to remove dust or residue. Let dry.

3.  Depending on the type of exposure, apply a primer (some clear, some pigmented) that is recommended for adhesion to plastics or hard to coat surfaces.

4.  Finish with appropriate finish coat.

A sample should be prepared before doing the entire job.


Painting Glass

Glass is very difficult to paint and, at best, should be considered a temporary solution. Glazed tile is often painted as a way of changing the color. Sandblasted glass, as opposed to smooth transparent glass, affords better adhesion to paint.

Painted glass often is subjected to heat shattering due to excessive absorption of heat by dark colors applied to glass and exposed to sunlight (i.e. showrooms). If painted, always coat the outside surface to minimize heat shattering.

Emulsa-Bond and XIM specifically claim adhesion (priming) on glass or tile, providing a “bonding coat” that can then be top coated with oil or latex products to extend the life of the coating.


Painting Fiberglass

New fiberglass must be thoroughly cleaned and all mold, wax, oils and surface gloss must be removed. Scrub with household cleanser and rinse. Use a “wet or dry” abrasive sandpaper and sand to remove all gloss. Rinse thoroughly and wipe down with a mixture of one part alcohol to one part water and allow thorough drying prior to painting. A 100% Acrylic finish provides good results on normal household applications such as awnings, windbreaks, patio covers, room dividers, etc (flexible surfaces should not be painted).

Weathered fiberglass normally has lost its gloss and exhibits a rough exposed loose fiber surface. Follow the directions on “New Fiberglass” dispensing with the cleaner scrub unless the surface is oily. Sand sufficiently to remove the loose fibers rinse and let dry. Prime surface, then topcoat with a 100% Acrylic paint.

Previously painted fiberglass normally only requires cleaning to wash off excessive chalk, sanding glossy surfaces and feather sanding of any loose or flaking paint. Touch-up bare spots with the selected finish coat, let dry, and then finish as required.


Painting Aluminum

A relatively easy substrate to finish if proper preparation is followed. Often inquires are made at a retail level on how to finish aluminum (i.e., trailers, siding, awning, storm sash, etc.) When finishing previously painted aluminum you are not coating aluminum you are coating paint. Be sure and follow proper surface preparation techniques and proceed as with any paint job. New aluminum surfaces will have a protective film from the factory which must be removed to insure proper adhesion. If this is raw (uncoated) aluminum it is recommended to clean and treat the surface using a chemical cleaning and etching solution. These type of products not only clean the aluminum but also provide a “conversion coating” that will promote greater adhesion of finish coats. Old aluminum surfaces may have oxidized and will require cleaning similar to new aluminum. A concentrated solution of Tri-Sodium Phosphate will remove oxidized salts from aged, bare aluminum. After any preparation solution, rinse thoroughly prior to painting.

  Follow the directions on the container making a special effort to rinse thoroughly with clear water to remove excess solutions or salts. Clean surfaces will “sheet” water while contaminated surfaces will cause water to “bead” . The clean surface may be coated using either oil or latex system.


Painting Acoustical Material

Modern construction depends a great deal on acoustic materials as sound containment or sound control either in residential or commercial application. These materials are either mineral in nature or more recently have included synthetics as an economical material. There are many forms of these products available but the one thing they have in common is porosity and cavities that capture sound. In new installations, these products usually do not require a coating. The acoustical plaster is tinted to the final color before application and the ceiling panels are factory finished. Practically all on site finishing is limited to the repaint market.

  To repaint acoustical materials, the object is to retain the porosity and cavities (to keep the sound deadening properties) while applying a new, decorative coating. this is best accomplished with flat latex rather than a higher sheen product. Harder drying, low sheen to high gloss materials will reduce the efficiency of the sound reduction. The flat finishes will provide a more uniform appearance without amplifying the inherently inconsistent surfaces of acoustic materials.

  Acoustic plaster is best finished with airless spray. Using highly pigmented flat latex paint. Normally, this material is reduced with water to prevent bridging and give easy flow into the acoustic cavities. The reduced material is thin and may even be applied with H.V.L.P. spray equipment. Two coats are usually required and should be applied in opposite ( crisscross ) directions to eliminate shielded or shadowed appearance.

  Acoustical panels are rolled almost as easily as sprayed ( using a 1″ or 1 1/2″ nap synthetic roller ). Again, two coats are recommended, rolled in opposite directions. In most cases, washing the surface prior to application is not necessary or feasible due to the delicate nature of the plaster and porosity of the panels. If washing is desired, a TSP solution or laundry detergent is suggested. Any water stains should be sealed with pigmented white shellac ( available in aerosol containers ) or a high quality water based stain blocker prior to finish.