by Rick Hill
Q.
I would like to know what you think of the application of linseed oil and turpentine. My father has done a lot of restoration and reproduction. I've found all of his advice accurate and useful.
I have a customer who has used linseed oil and turpentine to seal some doors in his new home. The doors have since warped and though they are still under warranty the seller says they are not "sealed properly." I would like your opinion.
A.
Linseed oil was the finish of choice in your father's day and still has some uses today, but when manufacturers talk about sealing a door, they are referring to today's film-forming finishes.
The following excerpt from Bob Flexner's book "Understanding Wood Finishes" (Rodale Press) explains the problems with linseed oil as a finish.
"Linseed oil is extracted from the seeds of the flax plant... as it cures it changes from a liquid to a solid by absorbing oxygen from the air. Linseed oil absorbs so much oxygen when it cures that its weight increases as much as 12 percent... Oils as finishes have certain characteristics in common. They cure slowly compared to every other finish... and they cure soft. Of all finishes except wax, linseed oil is the least protective. It's a soft, thin finish, so it provides no significant barrier against scratching. It's also easily penetrated by water and water vapor. Liquid water will work through a linseed oil finish and cause a smudge within 5 to 10 seconds. Water vapor will pass through a linseed oil finish almost as if it weren't there."
So, when a manufacturer talks about sealing a door, they are referring to film-forming finishes (like lacquers, varnishes, etc.) that slow the absorption of water into the wood, preventing warping, swelling, cracking and splitting of the wood surface.
I would have to agree with the manufacturer -- the doors were not sealed properly.
Rick Hill is an independent representative and consultant for industrial wood finishes. He has been involved in the woodworking industry for 12 years, and has been known to actually hold, shoot, and clean a spray gun.
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