Filling Pine Wood Knots?

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kellyh88's picture
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Joined: 2010-08-31 04:46
Filling Pine Wood Knots?
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I'm very new to this woodworking thing. The bug has bit and I love it!

I've only stained one item and it was oak, so I didn't have to worry about knots in the wood. I'm going to build the farmhouse table soon out of pine and I plan on staining it. Is there something clear I can use to fill the knots on the wood to make the tabletop surface smooth and flat? Has anyone used a product that filled knots in wood? How does it work? Before the stain? After the stain? Any input would be greatly appreciated!

jokunokun's picture
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Joined: 2011-03-01 16:21

There are products called wood grain fillers that are used to fill the wider, more open pores in woods like oak. They're used when the goal is to get a nice smooth surgace, without the wood grain texture coming through. I've never used any so I can't recommend a particular one or give any adivce on how to apply it, but you can see if your local hardware place carries something like that.

Googling "wood grain filler" will bring up a lot of info and can probably point you in the right direction.

claydowling's picture
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Joined: 2011-01-26 17:28

There are two products which are useful. I've used two-part epoxy very successfully, but be warned that in larger holes it has a sickly green cast. You don't notice it in smaller quantities.  It's also easy to scrape or plane. Sanding is slightly annoying, but if you give it a few days to cure it won't be a problem.  Epoxy is your single best bet if you have a knot that's a bit loose.

Auto-body filler is the other big winner. You can tint it to whatever color you want, and it sands easily. My dad uses it when he has voids to fill in oak.

Be careful when choosing wood to avoid knots in structural pieces, such as support rails on the table. A knot is a weak point in the board, and if the piece is to support a load across its width, it will probably break at the knot.

tmchoops's picture
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Joined: 2011-02-03 11:17

If you are going to stain pine make sure that you get "stain grade" pine and not "paint grade". You will not have as many of the big knots. There will also be a little more expensive pine that will have no knots at all (you get what you pay for)...it is still MUCH less expensive than oak. As for the filler they do make stainable wood filler, there are several companies (I have used elmers and it works good).

The better product you start with the better end result you can expect, especially when staining.

hillarylouise's picture
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Joined: 2011-01-21 19:59

I researched this a few months ago and found lots of posts about using a two-part epoxy to fill knots but keep them recognizable as knots. I think that is a great option -- it would give great depth to the table, I think. When I was reasearching it, I didn't see anything about the epoxy turning green -- maybe it depends on the brand? Instead of epoxy, I ended up using Timbermate wood filler (which I looooove but where I live I can only find it at Woodcraft, definitely not at Orange or Blue). I used black Timbermate to match the color of the perimeter of the knot holes and then stained and tung oiled the whole thing (it was a floor, actually). It turned out great. I couldn't be happier. If you decide to use regular filler and have it match your stain, either buy filler that is already colored to match your final finished color (stain a piece of scrap and take it with you to the store) or add your stain to tintable filler before filling the holes. No filler takes stain well after the filler is dry, not even "stainable" filler.

claydowling's picture
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Joined: 2011-01-26 17:28

I was surprised by the gree cast as well, but I've seen it in two different brands.  I haven't seen it when I used epoxy in the past, so maybe common formulations have changed, or just the brands available to me have changed.  Like I said though, it takes a pretty big hole before you can see it, and even then you have to be paying attention to the hole before you actually see it.