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2 posts from August 2010

Monday, August 16, 2010

Advice from the Pros:

Stain Stoppers: Primers That Block Bleed-Through

wood knot bleed

Stains or bleed-through present special challenges and often call for special primers and/or specialty sealers. An effective blocking product depends upon the problem stain and on the finish material. But with all of the possible stain offenders (wood knots, smoke, soot, ink, crayon, lipstick, tannins, oils, watermarks, rust, etc.) and the vast varieties of primers, what's a painter to do? Here are a few guidelines on how to choose the right primer/sealer to stop the problem stain:

  • First, is there a difference between a primer and a sealer? Yes, a primer provides a foundation for adhesion and coverage of the finish material, while sealers are formulated to suppress stains.
  • What is an underbody? An underbody is an alkyd or acrylic primer that is heavier-bodied, allowing you to sand it to a smooth finish before applying an enamel paint (typically on wood). Its perm rating (less than 1) means that a film of Alkyd Enamel Underbody not only blocks stains, it also acts as a vapor barrier.
  • Which is best: acrylic primers or alkyd? That depends. If the offending stain is an oil-base substance (such as crayon, soot or a build-up of skin oils), a water-base (acrylic) primer is less tolerant. Spot-prime these bleed-through problems with oil (alkyd) sealers.  A solvent-thinned primer, such as Benjamin Moore 024 Fresh Start All Purpose Primer suppresses wood knots, smoke stains, and water marks for interior applications.
  • Are fast-drying primers best? Fast drying primers have the advantage of being ready to topcoat soon but will become brittle. But slow-drying (alkyd) primers penetrate better into the substrate, and they remain more flexible, offering better penetration and adhesion.
In all cases, you want to stop the stains and block the bleed-through--because whether your goal is to have a change of color, to add a layer of protection or to refresh a worn finish, one thing you don't want to see on your finish coat is any telltale sign of what lies beneath.

Tuesday, August 03, 2010

Advice from the Pros:

Finishing Hardwood Decks

Staining hardwood decks 

Decking and outdoor furniture made of exotic hardwoods (mahogany, ipe or teak, etc.) are uncommonly beautiful--and they require uncommon care. Unlike their more porous cousins (softwoods such as pine, cedar and redwood), hardwoods do not absorb finishes in the usual way. In fact, they don't absorb the usual finishes. If you own hardwood decking or patio furnishings, here are six key tips for their care:

  1. Start with the right finish. We recommend an alkyd stain made especially for hardwoods (Benjamin Moore product 321), a transparent finish designed to bring out the natural colors of the wood. Incorporating a very finely milled pigment, this product will penetrate dense, exotic woods, rather than coating them with a surface film.

  2. Don't over-apply the finish. Hardwood absorbs only so much material--no matter how long you let it soak. This brings us to pitfall #3:

  3. Don't leave excess material standing on the wood. Apply a minimal amount and wait no longer than 15 to 20 minutes; then wipe off the unabsorbed "residue" using a pad or a rag. Any more time, and the finish begins to oxidize and will ultimately fail. This is not a case where more is better.

  4. Maintain a wet edge. Work along the entire length of the board so you can keep a wet edge. You may be able to coat and wipe off two or three boards at a time, as long as you can stay under the 20-minute soak-and-remove time as you go.

  5. Watch the weather. As with applying any outdoor finish, never work in direct sun or extreme heat. Check the forecast and postpone your project if rain is anticipated within 24 hours.

  6. Repeat as needed (every one to two years, depending on the surface's exposure to sun). If the wood has turned gray (a sign of dead wood fibers), you can treat it with a brightener or restorer using the same procedure as for softwoods. Then apply a finish to bring out the wood's natural beauty and color.