minimizing wood movement due to humidity

[Scott Perkins47]

I've been thinking that wood containing a lot of oil that wont
dry out would not change in dimension so much with
changes in humidity. I think if the wood has a lot of oil
in it, then it would not soak up moisture from the air.

Since I found out baby oil was mineral oil with fragrance
added, I have been using baby oil on all my antique furniture.

I use to stain and polyurethane all my projects but these
days I am just staining and using a non drying oil.

[Alan Schwabacher]

Do you really want your woodworking projects to smell like baby oil? And to leave oily smudges on things they touch? I don't think it will be very effective at preventing expansion and contraction unless it's so full of oil it will tend to drip out.

[Richard M. Wolfe]

I'm afraid that you (or a customer) may be unhappy with some things set on the oiled surface (especially for any length of time or under pressure).

[Steve knight]

it does not work. even if you use a vacuum to pull the oil into the wood it does not stop moisture from entering. only things that work is heavy coats of epoxy or wax.

[Michael Schwartz]

Wood moves and there are enough established ways to accommodate its movement that it is so routine and easy to just allow it to do so, once you know a few basics. Well designed furniture has the potential to last through centuries of expansion/contraction from seasonal movement.

[Scott T Smith]

The flooring in my home is heart pine planks made from beams that came out of a large textile mill in Kanapolis, NC. This mill was very old - with parts of it dating back to the 1860's. My flooring planks vary between 4" - 6" in width, and were installed in the traditional manner (flooring nails through the tongue - boards installed over roofing felt paper on top of the subfloor.

The particular beams that my flooring came from were once installed as the subfloor in the machinery rooms where the mill had their cotton presses. Consequently, over the years the entire floor in that area became saturated with cotton oil, as did the subfloor beams.

Most of my flooring boards are still saturated with the oil. It does not "drip out", but you can tell by the way that the raw boards feel, touch and weigh. I have 400 bd ft leftover from the flooring installation stockpiled in the basement for any potential future needs.

The floor is coated with a "moisture cure polyurethane" sealer. There are no problems with oily residue or with the finish lifting.

However, I have not noted any decrease in the wood movement - there are still some small seasonal gaps that open up in certain portions of the floor.

[Lee Schierer]

It really isn't possible to stop seasonal wood movement due to moisture changes. You can design around it and you can minimize the effects by applying equal amouonts of finish to all sides. Even the best penetrating oils only go a few thousandths of an inch into the wood.

I routinely aply finish inside and out on the furniture I make. That way the mositure changes occur more uniformly.

[Eddie Darby]

Wood is made up of molecular units called Cellulose, but Scientists jokingly call it Swellulose. There is a number of people pursuing the creation of new materials, that will mimic the characteristics of wood, but will not swell. So far they have largely been unsuccessful, but it does show you how desirable wood is.

The basic affinity that cellulose has for water will not change. Not all woods have the same swelling properties, so you could use more stable woods. This is due to the way the wood fibers are laid out. You should be able to find wood swelling tables. See page 25 from this link.

http://www.ces.purdue.edu/extmedia/FNR/FNR-163.pdf

Using oil, or for that matter any finish merely slows down the reaction time to environmental changes. Once the water vapor gets past the coating, and it will, the wood swells. Slowing down the absorption rate though will help with seasonal changes, since most conditions are only short term. So checking on the effectiveness of coatings will help, since some are better at doing the job of slowing down water penetration than others.
Just follow the time tested traditions of coping with Swellulose, and everything should be fine.

[Tony Bilello]

If you were concerned with the moisture exchange between the wood and the air, an oil finish is the worse protection of any kind of finish. Dont believe it? Splash coke or anything wet on an oil finish, a poly finish, a shellac finish or lacquer and tell me the results. Or even beter, put one end in water for a few hours and see what holds up best. If it takes in moisture, it will swell. BTW, on really hot days, the wood will sweat out the oil.
There are two things to consider with furniture. One is that movement should be planned into the design of furniture and two, with a hard finish, moisture will eventually penetrate through it, but the normal everyday exchange of moisture is so slow that it is negligable.