Thread: Best way to treat and fill knots?

I have used both superglue and epoxy, but these days generally use epoxy. Often the epoxy will be mixed with fine sawdust of the right colour.

It is also possible to buy pigment, but I have never done that and will allow others to comment on its use.

Epoxy works well - just be sure to cover the reverse side with packing tape if the defect goes through the board. Feast & Watson proof tint works well to dye the epoxy if you so desire. If you want the smoothest epoxy fill job, scrape or sand the surface until tear out and any other removeable imperfections are gone. Unless you tint the epoxy so heavily that it becomes opaque, any defects in the surface will still be visible.

Further to what's been stated above, yes collect/save sanding dust (saw dust is too coarse) and mix it with whatever your chosen lacquer finish will be and work it well into the blemishes. Don't use or mix with wood glue as it will comeback the haunt you. Also this post maybe of interest to you Pin holes/bubbles in NC lacquer - Page 2 (woodworkforums.com)

I have used epoxy with good results. Use a heat gun, or propane torch to draw out bubbles..works a treat.

Thanks for the comments! Sounds like I should try epoxy. I've watched a couple of videos and was a little concerned about possibly affecting the finish where epoxy flows over surrounding wood, although it looks like it cleans off OK.

I'll continue with a bit more dimensioning now before filling the knots and a final pass through the thicknesser. There looks like a supplier of West System epoxy not too far away. The Protite casting resin listed at Bunnies has a fairly poor review score.

Originally Posted by Fuzzie

There looks like a supplier of West System epoxy not too far away. The Protite casting resin listed at Bunnies has a fairly poor review score.

I use West System epoxy. Works for me, both as a glue and as a blemish filler. Some blemishes in "wild grain" veneers can be quite large, but the wildness in the grain means the epoxy and fine sawdust repair all but disappears. When repairing knots (such as noted in your pic) it seems that being slightly too dark works better than being a bit too light when colouring the epoxy with sawdust (or pigment, I suppose). Repairs that are too light scream at the viewer.

I use sawdust I have scavenged out of nooks and crannies in the table saw, and keep a few jars of different coloured sawdust. First I put it through a flour sieve, to produce a reasonably fine product. If I want it even finer I set up an MDF inclined plane, pour the sawdust along the raised edge and then tap the MDF with a mallet. The sawdust "jumps" down the inclined plane with each tap, gradually separating the fine from the coarse material. For larger repairs, the flour sieve (bought in most supermarkets) provides a great product to mix with the epoxy. I want some of the bigger chunks in there to give the look of texture. For small repairs a finer product generally works better.

When I was routing out the top of my router table for the insert the double sided tape on one edge gave way, but it did so gradually so that I didn''t notice for a couple of seconds. Had a large tapering gap to fill.
What I did was fill with Timbermate and when it was dry soaked with thin superglue. It's held up really well even on the edge.
I believe I seen this on youtube somewhere but no idea who to credit.

I purchased some West's today from the local distributor and had a bit of a chat to the tech guy there about colouring. I have a packet of black cement oxide pigment left over from some brickwork repair I did a while back and apparently that will be quite alright to use. He wasn't supportive of using sawdust/mill flour.

Along with 5min epoxy from Bob Smith Industries for larger cracks and holes.
I’ve started using Starbond Medium Thick CA with accelerator to fill small to medium size cracks and holes.
The beauty of the Starbond is that it can be built up in layers then sanded immediately.
Works great!
Cheers crowie

Originally Posted by Fuzzie

The boards I am using on my current project have some knots. On previous projects I have occasionally used Timbermate to fill small defects like nail holes and such and that has simply been applied just before the finish. These knots are in boards destined for a table top and I suspect they might be best filled with something other than Timbermate and before I continue with the dimensioning.

What suggestions are out there for stabilizing knots like these? Is this something best done with epoxy or is some sort of Superglue OK. Which brands to use for small quantities? And how do you tint it?

knot1.jpg knot2.jpg

The danger with knots, apart from the aesthetics, is that they will "pop out" later.

My solution for smaller knots, as in your second photo, Franklin, is to drill out the knot and insert a plug cut from the same timber with a Veritas plug cutter, and aligning the grain as far as possible.

For larger knots, as in your first photo, I chisel out the knot and make a plug to fit, from the same timber. Shipwrights call these plugs "dutchmen".

There may be hollows running from a knot (eg sap pockets). In this case I use gap filling WEST epoxy thickened with sander dust as glue. If the hole is clean and tight fitting, then PVA is more than adequate.

WEST advise against using saw dust and sander dust as filler/thickener. I wonder why? A free product competing against their microfibres, microballons, microspheres, colloidal silica, etc. I use sander dust because it works just as well and gives a better finish!