Sealing cracks in old timber for oil finish?

[Gunnaduit]

I've been working on some recycled 8"x4" bridge timber, which I dressed smooth.

Where it deeply weathered in its past life as bridge decking, there's black cracks which I don't want to hide, but I do want to fill. Some cracks are almost 1mm wide.

Then I'll sand it all down and oil it.

But what's good to fill the cracks before I oil?

Something other than plastic wood putty. Maybe some natural product?

[geoffo]

G'day Gunna

As a very amateur woodworker what I would try on an offcut of the timber is a paste made up of some sawdust from the bridge material and Aquadhere. Obviously the paste needs to be of a consistency that is not runny or stiff.

It's worth a try - the cost of it will be nil!!

Geoff

[Tung tied]

Hi Gunna,

Resin or epoxy is usually used, typically black but I've seen some work using clear so you can still see the detail in the cracks. You have to take a bit more care sanding it as it can be harder than the wood, not sand off as quick as the surrounding timber and lead to high patches. I use black putty and it seems to work well for me.

Cheers

Bryan

[Gunnaduit]

Gday guys, thanks for those responses. Didn't check the forums for a few days so a late response here. Thought nobody would ever reply.

Yeah, PVA glue with sawdust. Maybe, although I've heard it isn't reliable, that it can end up coming out of the crack. Nothing to lose in trying it I suppose, except the finish when it all starts coming out. Hmmm.

If I went with the PVA+sawdust mix, might as well use plastic wood putty, its probably a better formulation of about the same thing.

Carbatec fella reckoned that West System epoxy was the only thing that would work, because nothing else is flexible enough to follow the movement of the timber around the crack. Good, but shelf life is 12 months and I reckon the rest of the $37 tin will just get wasted.

He also reckoned that hide glue or shellac used as filler would just crack out, that the only reliable thing is epoxy.

Monaro timbers (Canberra that is) fella reckoned everyone's using casting resin for filling knots etc. Yeah, ok except the MSDS says its carcinogenic and kills cats. Well I used up my nine lives ages ago so I can't stand any MEKP/resin kind of stuff - just won't touch it.

So well I don't know. I suppose when I oil, and wet-sand the oil into the timber, the goop on the sandpaper will go into some of the smaller cracks, while the bigger cracks will just stay open.

I don't think any of this looks like the perfect idea. Maybe someone's still got a better idea, or thinks I missed out something or got the wrong end of the stick in all the above.