02-15-2011 07:22 PM
I applied boiled linseed oil to maple with the intent of top coating with garnet shellac in one week. The surface is extremely blotchy. Should I recoat with linseed oil or will the shellac even out the appearance?
02-15-2011 09:00 PM
BLO on maple... some call that character; or popping the grain.
On thin edge grain, it can look great; on large flat pieces some wont like the look. Garnet shellac may mellow it a bit.
Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.
02-16-2011 02:57 AM
I see that this is your first post to the WOOD Magazine Finishing & Refinishing Forum. I hope you will visit often...
I don’t know how you applied the BLO and I can’t see the maple (photos are always helpful); but, I will offer a couple of thoughts with respect to your finish schedule and your observation that the surface is “extremely blotchy”. You asked if you should recoat with the BLO. That depends on how you applied the oil in the first place. When applied to diffuse porous hardwoods like maple, BLO works best when applied liberally so as to give the wood all of the oil it wants. It should then be allowed to soak into the grain for 25-30 minutes with the excess oil then wiped off and the surface wiped dry with clean shop towels. If you have applied sufficient oil and given it time to penetrate into the grain structure of your maple there will be nothing gained by another application. If you have been stingy with the oil another application may help. (As an aside, BLO will cure in 8 to 12-hours under “normal” conditions. If you want to wait a week you certainly can; but, it isn’t necessary.)
But, it is more likely that the so-called “blotchy” look has little to do with the BLO and almost everything to do with the maple you selected for your project. Maple frequently exhibits figure resulting from a condition described as “wavy grain”. (Wavy grain results in areas of different pore diameter and density being exposed on the surface of your lumber). When the occurrence of wavy grain is uniformly distributed over the length of a board and its occurrence is tightly packed woodworkers prize the lumber as “curly”. Applying finish, especially oil followed by shellac, dramatically accentuates this curly figure. But, while curly lumber is rare and desirable, when the same wavy grain is irregularly distributed and widely spaced over the length of a board, applying the same oil/shellac finish will still accentuate the “figure”. Its look however will now be described as “blotchy”. Virtually any finish applied will accentuate wavy grain. Whether it results in “curl” or in the far less desirable “blotch” depends on the distribution of the wavy grain.
While it’s a bit late now, the best way to disclose wavy grain (what I prefer to call “latent figure”) in maple and other diffuse porous hardwoods with a tendency toward “blotching” is to apply a coat of paint thinner (mineral spirits). If figure (or “blotch”) is present the paint thinner “finish” will accentuate it (even in rough lumber) thus allowing you to either reject the board or use it in a way that takes advantage of the “figure”. (The paint thinner will evaporate and have no impact on whatever finish you ultimately apply.)
Applying more oil at this point may bring out additional “figure” if you did not apply it liberally the first time. If you did make a liberal application and give it time to penetrate, then more oil will not help. Added oil will not remove the figure; it can only more completely accentuate the figure that is there. My suggestion would be that you complete your finish schedule. As Scott has suggested, the BLO has resulted in “character” by accentuating the grain and figure of your lumber. To some the look is “blotchy”; to others of us it is desirable. Either which way, it comes with working wood…