What to fill knot holes with?

[Toller]

I bought some walnut at an auction and am using to build a large cabinet. Well, the bargain wasn't all that good cause the wood is distorted and full of knot holes. There are two that are completely though the piece, and they have fallen out, so it is just a hole. I can stick them on the side that goes next to the wall so they will never be seen (except from the inside, and then not very well), but what do I do with them. I have to fill them with something. It seems too big for wood filler. Any way to make a walnut colored filler that will stay put; maybe mixing walnut dust with epoxy? Or cutting a hole with a hole saw and somehow making a plug to go in? Even though they won't be seen, I would still like them to be as nice as possible.

I got the walnut at about 1/3 of retail, but had to do a lot of extra planing (fortunately it was 5/4) to get down to good wood. I should have saved it for a project where I could cut around the defects, but misjudged how bad it was.

[Lew Hodgett]

RE: Subject

No matter how you try to match a filler color with the walnut, the results will SUCK.

It will look like a little kid who got caught with his hand in the cookie jar, IMHO.

What about a contrasting color like filling the entire hole with BLACK?

If you think that will work, get back to me, tell you how I'd do it.

Lew

[Toller]

Okay, black could work. How, what?

[fredfighter]

I'm not the guy you're asking, but here are some suggestions (his will probably be better).

You can use auto body filler (bondo) or spackling compound or mix sawdust with epoxy and then after the patch is cured and planed/scraped/sanded smooth paint it. If you feel really artistic you can get some artists' oil paints and a a fine brush and paint a knot on the patch.

ISTR that you can mix tempura paint pigments directly into epoxy.

Then there is JB Weld...

[Lew Hodgett]

You will need the following materials.

1 gallon kit of epoxy, some black pigment, and some micro balloons.

Don't know where you are located, but there lots of epoxy suppliers out there, especially for a job this size.

Supplies:

Single use latex (Medical type) gloves, paper cups, lots of clear packing tape and paint mixing sticks.

You want to make what I call a backing plate.

I use scraps of 1/2" CDX plywood covered with packing tape.

(Epoxy doesn't stick to packing tape)

These backing plates are then used to block the bottom side of the hole.

I attach them temporally with screws. If that will be a problem, use C-Clamps, bricks, whatever, to hold the plates in place while the epoxy cures.

Mix up small amounts of epoxy thickened with micro balloons that has also been colored and fill each hole about 1/2-3/4 full, then let cure for 24 hours.

Next day, finish filling holes proud and let cure.

Turn board over, remove backing pad which will release easily because of packing tape and fill proud as required with more thickened epoxy.

Let cure, then sand flush with some 40 grit on a ROS.

Why the multiple pours, you ask?

Several reasons.

Epoxy is an exothermic material. Pack too much in a hole, it will take off, foam and have to be removed back to the beginning.

Multiple pours insures no voids and a 100% fill.

Building a boat, I've done the above so often, I could do it in my sleep.

It's not rocket science.

Good luck.

BTW, micro ballon thickened epoxy will destroy cutting tool edges.

Plan accordingly.

Lew

[Guess who]

It's called low-grade wood. Avoid the holes and cut to use for small projects. If still not enough, accept your lot and be wiser next time. I got a piece like that among some other good stuff, but it was free, so no loss at all. Enough for a few good small projects though.

[nailshooter41]

For another look at this knotty problem... ouch... I do something different.

I fill mesquite regularly as it is quite accepted to do it down here in South Texas, even on fine furniture. Not the finest, but fine.

I do a lot of turning, and the most intersting wood to me is the most messed up, butt nasty ugly stuff I can find. I comes with large wind shake rings, borer holes of about 1/4" diameter, and all manner of other distresses.

I use epoxy, but in a different way. I mix up the epoxy, make my dam (tape, etc.) so it doesn't flow out, and mix up epoxy with copier toner. This makes the epoxy perfectly jet black. For a more natural feel and look (instead of black plastic) I mix in a medium grind coffee. The coffee actually seems to hold the finish on better than the plain epoxy and doesn't have that plastic look to it. Coffee is also harmless to planer blades, jointers, and turning tools.

Some of the guys also put in colored stones, Inlace (available at WoodCraft), key filings for a soft brass glow, and all manner of other things.

Everyone in my turning club has their own method of doing this, but this is not much of a deviation of the norm we all have been doing for a long time. Oddly, the black epoxy looks better on large pieces with no coffee grinds, if is half and half on the smaller ones, and almost anything turned that is a medium brown to cherry looks better with the grinds. Whiter woods look better with only the epoxy/toner combo.

It should be noted that unlike Lew's instruction above, this is not for a boat, or any other kind of structure or work surface. It is simply a quick way to make imperfections more palatable, or in the case of woodturning, a feature.

Robert

[ROYNEU]

Lew,

Back some time ago I had started looking for what kind of tinting agents were compatable with epoxies. Can you fill me in?

Roy

[dadiOH]

That will work. So will regular glue. In either case, just back up the hole with masking tape and then pack in the filler. Result won't look great, can be improved (IMO) by using a mixture of joiner shavings, saw dust and sanding dust. Just enough glue to wet the wood fill materials. May need more than one filling.

-- dadiOH ____________________________

dadiOH's dandies v3.06... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at

[Duke of Burl]

[Wes Stewart]

Are you trying to be punny?

[Bob S]

(I'm posting this way just say Larry won't pick on me about my top-posting habit....;-)

Toller,

Lots of good info from others but no mention of using artists acrylics. I've used black and ocra mixed together with epoxy and you only need enough mixed in with the epoxy to color it. Stark black looks good but the dark ocra gives a hint of brown that looks like knot wood. The nice thing with using the acrylics is that they're inexpensive and you can just mix them together to get the exact tone you want before adding the color to the epoxy. Fill the hole in layers to insure a good fill and cure.

If the finish is ultimately going to be a flat or satin low-luster finish then sand the epoxy filled areas so they are opaque (not shinny) and when you apply the finish, they will blend in nicely. Be careful when sanding though. The epoxy is much harder than the wood and if you're not careful you will sand the area around the knot holes lower than the epoxy. Best to over fill the holes ever so slightly then use a single-edged razor blade as a scraper to scrape the epoxy down level.

You may want to drill a couple of holes in some scraps and practice a few, I think you'll like the result. I've also used butterflies to cover.... make that, enhance an imperfection. Use the inlay set (Lee Valley, Rockler...) to do that as someone recommended.

Bob S.

[ROYNEU]

Real question and all puns intended. Now Woodcraft is an example of what I've been finding where I've looked. In the information they never tell you what the tint is made from so I can go looking for other manufacturers. And, where I've looked so far they never carry a full line of color. Woodcraft says there are six colors yet they only carry two of them.

Anybody know what this stuff is made from?

[Toller]

You are certainly correct in general, but in this particular project any wood that will actually be seen doesn't look too bad; just one very solid knot. The bad stuff is all up against a wall, so only the edge will be seen. I could probably leave holes and no one would ever know.

I just want to fix them because I will know, and for the practice of doing it.

[Toller]

You have used both epoxy and yellow glue? How does epoxy sand and react to varnish? How well does yellow glue last?

I see yellow glue sanding and taking varnish better, but epoxy being more durable; but maybe not. Perhaps I should make up some samples.

[Lew Hodgett]

My knowledge is very limited.

Used black epoxy as the first coat to seal some foam in the hull before applying a layer of glass.

Used black since it made finding pin holes easy.

My epoxy supplier sent me a quart of epoxy that was filled with carbon black.

My epoxy supplier doesn't do this themselves, it is a buy out fome somebody in Huntington Beach, Ca.

1 quart of black was enough to tint at least 30 gallons of base resin.

When it comes to other colors, I'm clueless.

Try talking to an ink manufacturer.

HTH

BTW, the idea of using copy machine toner to make black resin works for me, especially when using it to fill knot holes.

Lew

[Lew Hodgett]

That works for me. It all gets back to carbon black.

Since this is a non structural application, you can use almost anything as a filler.

Any filler will knock down the epoxy shine.

Some may improve the adhesion.

The microballoons I use are low cost, improve the adhesion of the epoxy, but are abrasive so they dull cutting tools.

Interesting ideas.

I'll bet you get some very neat results.

Lew

[Andy Dingley]

Epoxy is a pig to sand. Epoxy filled with the right filler (microballoons) is easy to either sand or scrape. Epoxy with the wrong filler (silica) is indestructible.

[Andy Dingley]

I use the phenolic (brown) microballoons, not the white silica ones. They're much softer and don't dull tools.

[Lew Hodgett]

For probably 90+% of the people on this list, that is probably a good idea to use the phenolic balloons since the usage is small.

I buy microballoons in 4 cubic ft bags(30 lbs), often geting several at a time.

The increase in cost of phenolic is significant.

Lew