Replies

1. 
   tmu | Mar 09, 2010 05:59pm | #1

   George,

   I use Stick Fast 20 minute epoxy, with a dot of colorant that I get from the local paint store, to fill knot holes in walnut and oak.  I've had no problems.  You may have to apply a couple of layers, depending on how it fills in the hole, or the voids left when it releases the air bubbles that are always present.

   Tim

2. 
   DonStephan | Mar 09, 2010 07:24pm | #2

   Especially in cherry with some black "pitch pockets" and/or lines, black epoxy blends in very well for small defects.  Not sure how well it will blend in if the hole is large.

   For tinting the epoxy I use black fresco powder (because someone gave me some colors years ago).  I think Transtint is a liquid and not sure if that will mix well with epoxy.  Transfast black might work well.

   If the hole is large, keep in mind that epoxy gives off heat as it cures.  A large ball of epoxy might get hot enough to char the wood.  Alternatively you can build in 1/4" layers and/or fill the interior with a piece of wood.

   Depending on the intended finishing schedule, you could use some powdered stains with shellac to add some color variation to the filled hole.

   Epoxy is very hard, and sanding without dishing around the epoxy is always a challenge.  I've found a card scraper to level epoxy extremely well, followed by light fine sanding if needed.

   Don't be afraid to drill a couple holes in some scrap wood and test-drive the epoxy plan.

3. 
   daverichards | Mar 09, 2010 08:25pm | #3

   Does the hole go all the way through?  If so, you might consider filling it from the back. Clamp a smooth piece of plastic (backed up with a piece of MDF or plywood) over the top side of the hole or cover a piece of MDF scrap with plastic packing tape. Fill with epoxy from the opposite side making sure to work the epoxy in to prevent any voids. When the epoxy has cured, remove the plastic (the epoxy won't stick to it) and you'll have a smooth surface without having to sand it down. You may need to sand it with fine grit paper to give it some tooth to hold your finish.

   If you are sanding it, don't get over zealous. Heat generated in sanding can soften the epoxy. Then it is like trying to sand chewing gum on a hot sidewalk in August.

1. 
   user-64052 | Mar 09, 2010 08:55pm | #4

   why not just fit a piece of cherry in there,to complicated?

   ron

4. 
   Quickstep | Mar 09, 2010 09:05pm | #5

   I've filled several knot holes with West Epoxy by just making a dam or taping one side and then pouring the epoxy in the hole. I've tinted it with colorant that's made for fiberglass repair like the stuff shown in the link below, but mostly I just use some sanding dust from the project mixed with colloidal silica. The sawdust alone usually ends up too dark, but it's a judgement call.  I've found that bubbles come from two sources when using epoxy to fill large holes. One of course is stirring, but I also found that as the surrounding wood absorbs the epoxy, the air displaced from the pores is released into the epoxy. If the slow hardener is used and you work relatively quiclkly, the bubbles will make it to the surface before the epoxy begins to kick. Heat from a light bulb will also drive out the bubbles. I overfill the hole an let the epoxy leave a slight "pillow" above the surface that can be sanded flush later.  Don't be too quick to sand it. Even though the epoxy gets hard pretty quickly, it continues to cure and shrinks a bit. If you sand it flush to the surface too soon, there will be a slight depression after it fully cures.

   http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/99770/377%20710/0/gelcoat%20repair/Primary%20Search/mode%20matchallpartial/0/0?N=377%20710&Ne=0&Ntt=gelcoat%20repair&Ntk=Primary%20Search&Ntx=mode%20matchallpartial&Nao=0&Ns=0&keyword=gelcoat%20repair&isLTokenURL=true&storeNum=95&subdeptNum=674&classNum=674

5. 
   RickW | Mar 09, 2010 09:16pm | #6

   I've filled knot holes in walnut with the West System epoxy. I colored it with the black and brown dyes they sell. I thickened it with Cab-O-Sil fumed silica.The deep holes took more than one filling.

   Rick W