Why the older the nail the more difficult to remove?

[Charles123]

Why is it that makes more difficult to remove a nail from wood as time passes? What changes in the wood?
Thank you
Regards

 

[Integral]

Depends on the wood. For my 10yr old fence, this is certianly not true.

 

[OmCheeto]

There are probably different reasons. I would imagine it's primarily chemical in nature, and some sort of petrification process takes place. I've a boat keel that is almost 70 years old, and the places where the nails went through are noticeably harder than the rest of the wood. That, and the fact that rust itself is abrasive, would add up to: sandpaper nails embedded in rock.

We should ask LisaB. She's a wood chemistry guru.

My knowledge of chemistry: Different kinds of atoms like each other, and form bonds. The end.

 

[Danger]

I don't know that the wood has the final vote in the matter. As Integral mentioned, my experience with old wood (and no, I'm not referring to my sex life) is that it tends to deteriorate in most instances.
My thought is that perhaps rust accumulation along the shank of the nail might act as "barbs" to make removal more difficult as long as the wood is structurally sound.

 

[fleebell]

I don't know about most woods as most of my experience comes from working on houses for years and most houses etc have used pine wood in the framing for a long time. Pine wood takes a long time to really dry out and for years it will 'breathe' moisture in and out. As it does this the wood fibers keep expanding and contracting and eventually will fit around a nail like a molded form.
Add rust, galvanizing or any surface coating and it's stuck in there pretty well. Another thing is over time the pine resin slowly dries out and hardens almost like an glue so what you essentially have is a rough shaped nail glued into a form fitting hole.
It isn't going to come out easily. Many times the nail will break off from strain from the pulling or rust before it can be removed from really old pine type woods.

 

[Danger]

Good point, Fleebell. For some reason, I was thinking along the line of barnwood or other "plank" type pieces. I've had a pine 2x4 glom onto a screw so tightly that the head sheared off when I tried to remove it. That had escaped my memory until now. I always drill pilot holes for screws, so the basic effect is probably similar to that of a nail without a pilot hole.

 

[Watchman2012]

I'd have to go with the Rust accumulation on the nail, it adds more surface area.
Seasonal moisture is adsorbed by wood (humidity in summer) and will rust nails over time.

although I do agree with Feebell & Danger that Pine resin will harden as well.
over eons it becomes amber...

 

[turbo]

When I was a kid (8-9 or so), my grandfather bought an old hotel/general store/stagecoach stop in the West Forks, and he and my father and I spent all of our weekends for the next couple of years disassembling that monstrosity. The adults spent their time taking that place apart while preserving all the boards and beams, and I was relegated to nail-puller first class. I still hate square cut nails. Man, they came out hard.

My father had intended to build a house with that lumber, but he ended up selling it to somebody else who wanted to build a house, and used the money to buy us a house across the road. Timber-framed, and cold as hell, but it was a house. He still lives in it. The lumber we salvaged would make restoration experts drool, including floorboards that were 14-16" wide, 8x8 timbers, and trim to die for. I hated Sundays, because the blisters from Saturday hadn't healed and they got my attention with every old stubborn nail. We had cat's paws and other tools, but my favorite was a mechanical nail-puller with a lever. If I could get a purchase on a nail, that thing was coming out.