Wood movement and sealing

[Grahamshed]

This will show how much of a woodworking newbee I am

Wood 'moves' because the moisture content changes..... I assume this to be true.

So.... If the wood is properly sealed with varnish, oil, or whatever, then moisture should not be able to get in or out. No ?

Therefore it shouldn't matter how green, or dry, wood is when you get it.

But I know it isn't like that in reality..... Why not ?

 

[Sgian Dubh]

Here are a couple of short answers that will get you on the way.

No finish is impervious to water at a microscopic level, ie, water vapour will pass through a film forming finish, although the film will slow down the passage of the molecules. Epoxy finishes are probably the least permeable of the film type finishes. Non-film forming finishes such as oils and wax, allow the passage of both water vapour and even gross water relatively easily.

Although your question didn't say so, there's an implication that you might consider applying a finish over green or wet wood. The problem with this is that wood finishes generally won't stick to wet wood. Wood generally needs to be drier at about 20% MC or below before most finishes will adhere. Slainte.

 

[espookid]

of course the previous post is quite thorough but there are some water based stains and paints that will take a higher moisture content although they will be affected as the wood dries

 

[Grahamshed]

Thanks for that guys. I hadn't really considered vapour. One of these days I am going to take up a nice simple straightforward hobby.
Anyone for origami ?

 

[RogerS]

....
Anyone for origami ?

I did but I folded.

Coat..get

 

[Grahamshed]

I think that is your coat over there. The one with the white tapes on the sleeves.