W&WP December 2002

Finishing Cherry Requires Special Care

Careful preparation and technique will improve the finish on this increasingly popular wood.

Cherry is well-known as a fine furniture and cabinet wood. But as many experienced woodworkers know, finishing cherry requires special attention, because it is susceptible to a blotchy or mottled finish if not treated properly.

Bill Altman, president of the Hardwood Plywood and Veneer Association, says his members have recently seen an increase in claims for defective cherry.

“Cherry has become very popular in the past few years,” he says. “And more people are beginning to finish it with lighter or natural stains. When dark colors were popular for cherry, flaws were hard to see. But when you use a natural or light finish, the characteristics of the wood are magnified.”

David Bailey, president of Numatic Finishing in Seattle, says proper treatment of the wood is key. “Of all the wood-related finishing problems I’ve investigated over the years, 95 percent are caused by lack of preparation,” he says.

The first step, Bailey says, is to sand the wood prior to finishing it. “People will tell you plywood comes pre-sanded from the factory, but it needs to be sanded again within 24 hours of finishing.” Both Bailey and Altman then recommend applying a pre-sealer — a thin, clear finish that absorbs into the wood. Pre-sealers are available commercially or can be created by thinning the sealer with eight to ten parts thinner to one part clear sealer.

After sealing, the wood must be sanded again before applying the stain or topcoat. If multiple topcoats are applied, sanding is necessary after each coat.

Finishing cherry requires extra attention, as these two panels from the same log show. The panel on the left was not pretreated with a wood sealer and has a blotchy appearance; only stain and a topcoat were applied. The panel on the right was treated with a sealer, followed by stain and a topcoat.
Additional steps are often required to meet certain architectural standards. Bailey follows procedures recommended by the Architectural Woodwork Institute in its Architectural Woodwork Quality Standards Guide. The HPVA also offers a tip sheet entitled “Helpful Hints to Ensure a Beautiful Finish on Wood Veneered Products.”

Pre-Sealing Can Prevent Uneven Finish
Cherry is susceptible to a blotchy finish if the wood is not pre-sealed. Ang Schramm, product engineer at Columbia Forest Products, explains, “Cherry often has a wavy grain pattern and slicing veneer from the log results in cuts that are both parallel and perpendicular to the grain. Areas where the cut is more perpendicular to the grain absorb more finish,” he says.

Schramm likens the process to staining a two-by-four; the ends absorb more stain than the rest of the wood, so they become darker. “The same principle is true when finishing cherry. The finish absorbs at different rates depending on the angle of the grain,” Schramm says.

Book-matched veneers also are susceptible to an uneven finish if not treated with a pre-sealer, Schramm says. Book matching is accomplished by turning over every other slice of veneer and matching the two pieces, producing a mirror-image grain pattern.

The finish can be uneven, however, because one side of the veneer has different absorption characteristics than the other. When veneer is being sliced, the side furthest from the center of the log, the tight side, compresses, while the “loose side” contains lathe checks that open the grain and therefore may absorb more finish. Pre-sealing helps reduce the “barber pole” shading effect in book matched plywood.

There is a way to detect cherry that’s likely to produce blotchy patterns, says Jeff Jewitt, author of two books and four videos on finishing and the owner of a restoration and refinishing company in Ohio. “If you wipe the wood with alcohol or mineral spirits, it will give you an idea of which area will turn dark when stained,” he says. He too recommends using a pre-sealer for cherry. When using oil-based and non-grain-raising stains, he says finishers can also use a technique called glue-sizing — applying a thinned glue solution that is sanded down before the applying stain.

Altman says the HPVA is currently developing a finishing seminar to educate people in the industry on how to correctly finish various types of hardwood. “End users will often return the product and say ‘there’s something wrong with this wood.’ But usually there’s nothing wrong with the wood. They just don’t want to go through all the necessary steps in finishing.”

Bailey agrees. “It’s the finisher’s responsibility to understand the characteristics of the wood he or she is about to finish and to prepare the wood properly.”

 

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