How to Tell the Difference Between Hard and Soft Maple

Ferrous sulfate solution applied to these sample boards turns the soft maple (left) a blue-black, and the hard maple greenish gray.

Q:

I was given some maple boards, but how can I tell if they are hard or soft maple? Also, what’s the best finish for each?
—Robert King, High Ridge, Mo.

A:

Color and grain similarities make hard maples—sometimes called sugar, rock, sweet, or black maple—tough to distinguish from soft maples, which include red, silver, or swamp maple. For a simple test to tell the difference, Robert, mix two tablespoons of ferrous sulfate (iron sulfate) in one cup of water and shake until dissolved. (You can find ferrous sulfate at many lawn and garden stores.) Wipe the solution onto a piece of the unknown lumber and wait a minute for the wood to change color. Soft maple will turn a translucent blue-black color. On hard maple, the surface turns greenish gray.

Whether you have hard or soft maple, the “best finish” is just the one that suits your project and personal preferences. To preserve maple’s light color, apply a non-yellowing, water-based finish. To bring out the pattern in bird’s-eye or curly maple while giving it a light amber color, apply boiled linseed oil and allow it to dry for a week before applying a clear film finish.

If you want darker colors, though, use a dye instead of a pigmented stain. Maple’s small pores don’t trap enough pigment to produce an even color without blotching. Unlike stain pigments, dye will fade with age, however, so apply a darker surface than you want for the long term.

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