Epoxy as Knot Filler Questions

[Jason Strauss]

I’m in the process of making a couple of desks – one for each of my daughters’ rooms. The lower part of the desk is poplar which will be painted white. The writing surface is made of alternating strips of walnut and hickory. I know, kind of high end for a couple of kids’ desks, but I’m trying to make some quality pieces and I have a source of free, but not endless, walnut and hickory.

After milling up the parts for the tops, there are a couple of knot holes and other small defects that, while attractive, take a little away from the true purpose of the piece – a flat, hard writing surface. I’ve seen Norm use what he called “marine epoxy” as a filler when he built a book case out of mesquite a few years back. He colored the epoxy with “graphite” to obtain a black hue and then sanded it smooth. It looked very nice when finished. I’ve looked at some epoxy products at Woodcraft, specifically SYSTEM THREE. They even make a black pigment. My budget for this project is quite literally next to nothing (only a couple of bucks from paint, finish and drawer slides). The SYSTEM THREE stuff seems very expensive to me and I don’t need that much of it.

So, here are my questions: is it possible to use some other, cheaper product for this purpose? If so, what? Must one purchase a special pigment, or is there some other cost effective colorant (I’d prefer black)? Norm used graphite, where can I get some of that? Must one purchase a special filler (SYSTEM THREE has several options), or is there an as effective, low cost alternative (like fine wood flour from the orbital sander)?

Any and all assistance would be much appreciated!

[doug faist]

Jason - for one or two very small knots I've used a little tube of "5-Minute" epoxy. I colored it with graphite powder (sold as a lubricant at the hardware store). Let it dry completely, at least over night, then sand and finish as usual. It seems to work quite well and saves the cost of the super expensive epoxy.

Have fun with your project.

Doug

[Rod Sheridan]

Hi Jason, I use regular epoxy, coulored with artist's pigments to make fillers of different colours.

The pigments I purchase are a powder in a jar, a few bucks for a lifetime supply at the rate I use them....Rod.

[Tom Hargrove]

I filled in some knots/defects in red oak using five minute epoxy available from the Borg. I purchased the small bottles rather than the small tubes.

I didn't color the epoxy. I tested on some scraps, and the uncolored epoxy looked fine in the knot holes when scraped and sanded flush.

I pour the two components of the epoxy in one corner of a sandwich bag. After twisting the bag to confine the liquid in one corner, mix the two together. I suppose that pigment could be added also. I cut a tiny piece of the corner off the bag to make an ad-hoc "icing bag." This allowed me to fill the knots/defects with a tiny stream of material without making a mess to the surrounding area. And I have no mess to clean up when I finish - I simply throw the bag away after it hardens.

[Stephen Edwards]

Someone here on SMC (sorry, I don't remember who it was) taught me a trick for filling shallow knot holes and voids that works very well. I don't know how deep your knot holes are.

IF they're not all the way through you might consider this technique. First, apply a coat of whatever finish in the knot holes/voids that you're going to apply to the finished piece. When that has dried, slowly build it up with CG until it's slightly proud of the surface. When that's dry, sand it flush with the surrounding areas and apply your finish to the rest of the piece. When I've done this, you can hardly notice the voids underneath.

You might try it on a piece of scrap that has similar voids as your piece in order to see if you'll be satisfied. Cheap solution if it works for you.

[Mike Lipke]

JB Weld (two part epoxy, slow cure) is already black.
Sold everywhere epoxy is sold.

[Dell Littlefield]

I have used 5 minute epoxy and colored it with india ink or black enamel paint. Both worked equally well.

[Brian D Anderson]

Definitely 5 minute epoxy. I've filled a couple knot holes with epoxy mixed with wood flour (as you mentioned from the ROS).

If you have a copier at work that uses toner (not ink), you can always break into that and borrow a little toner for the colorant. :D

I actually did just that for the antenna in this butterfly inlay - 5 minute epoxy mixed with black toner:

http://www.jfreitasphotography.com/Temp/IMG_8450.jpg

-Brian

[Joe Spear]

[QUOTE=Stephen Edwards

When that has dried, slowly build it up with CG until it's slightly proud of the surface.


What is CG?

[Kyle Iwamoto]

Using the sanding dust from the wood and 5 min epoxy is cheap, and should match the wood better than black. I don't think I've ever seen black knots. They're always wood colored. If you did it in layers, you can even add lighter/daker dust and the knot will look more "real".

[Jason Strauss]

Thanks guys! All the ideas sound great. The largest of the knot holes goes all the way through (~3/4") and is probably 3/4" at it's widest by 2" long. I think I'll be trying the 5 minutes epoxy and graphite option as I prefer the black. That being said, I will also check out the JB Weld product as that sounds like it will save a step. The "icing bag" approach will likely get used as well.

Thanks again! Seems like a guy can always count on the Creek for some answers!

[Brian D Anderson]

I'm sure you won't but don't forget to put a piece of tape on the other side of that knot that goes all the way through. I don't want you to epoxy your piece to the table! :D

-Brian

[Jason Strauss]

Thanks for the reminder, Brian!

[Ed Peters]

but, I prefer to use untinted filler on large voids. After the epoxy has set up and the finish has been aplied, the depth of the voids is magnified many times for a really unique and dramatic look.

Ed

[Cody Colston]

Using the sanding dust from the wood and 5 min epoxy is cheap, and should match the wood better than black. I don't think I've ever seen black knots. They're always wood colored. If you did it in layers, you can even add lighter/daker dust and the knot will look more "real".

Y'all must not have any Aromatic Cedar out there in Hawaii. It has lots of knots and most of them are coal black, especially when clear finish is applied. They also soak up finish like a sponge.

You can use most anything to color the epoxy. I have a pint of lamp black from the hobby store that, like Rod's coloring, is probably a lifetime supply. Ground up charcoal works well, too.

This afternoon I was filling a large void in the armrest of an Adirondack chair I was making. It was out of Eastern Red Cedar which is a maroon color when freshly cut. I mixed up the epoxy (West System) and instead of sawdust, used some maroon Suede-Tex flocking that I had left over from another project. It worked really well and matched the Cedar perfectly. :)

[Bas Pluim]

What is CG?
Coffee grounds. Great for coloring walnut. Almost everything you need to tint epoxy can be found in the kitchen - coffee, cocoa powder, paprika, flour, chili powder, curry etc. These additives give the epoxy some "body" that makes it easier to fill the knot/ hole too.

[Paul Ryan]

I use gorilla WOOD glue and usually mix in some of the saw dust from the cup on my sander. I have done this for years and it works great. The knot holes end up the same color as the finished wood so the they look like the other natural knots. The reason for the goriila wood glue is do to the fact that when it dries, with out saw dust mixed in, it dries clear. It doesn't have the yellow tint like other wood glues or the tan like titebond III. Dont forget it is the wood glue NOT the gorilla poly glue.

[Jason Strauss]

So, after hearing the suggestions yesterday, I purchased a few of "syringes" of 5 minute epoxy at the BORG. I used half of one to make up some test "black", and the other half I used to mix up with some wood flour from my ROS. Well, I ended up liking the final color that the hickory and walnut produced, so that's what I used. I might have time to sand off the excess tonight. I will post some pics of the sanded tops once I’ve got that step completed.

Again, thanks…