knots and epoxy

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Forum topic by Ads posted 08-05-2008 07:36 AM 4603 views 1 time favorited 10 replies Add to Favorites Watch
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15 posts in 3873 days

08-05-2008 07:36 AM


Something I’ve been toying with is the idea of filling in knot holes with clear epoxy to create an illusion of depth underneath a finish. Particularly holes that don’t go all the way through the boards. I’ve got some west system packets that are good candidates for testing this. If I’ve got any concerns, it would be that the thermal reactions from having a thick layer of epoxy curing could do some funny stuff to the wood. Has anyone had any experience with this kind of technique or look? It seems like other than Epoxy, Polyester casting resin might work, but I’ve got even less experience with that.


10 replies so far

View TomK 's profile


504 posts in 4108 days

#1 posted 08-05-2008 09:41 AM

I’ve used another brand of epoxy to completely cover a cedar stool destined to be a shower stool with good results. I wanted a thick enough layer (like a bartop) that water would not be a problem. It is definately a strong exothermic reaction, but it did not cause any problems for my project.

-- If you think healthcare is expensive now, wait until it's free! PJ O'Rourke

View NY_Rocking_Chairs's profile


527 posts in 3831 days

#2 posted 08-05-2008 11:04 AM

When the West system is used in a thick pour it tends to crack during curing. I had this problem on my first fish tank build, I poured some corners that were 3/4” thick, during curing they all developed stress cracks. This may be true with all epoxy-resins, but my experience is solely with West.

I suggest you do it in micro-pours of not more than 1/8” thick, since this is only an experiment though you could see how thick you go before it develops cracks.

You shouldn’t have any problems with the heat.

-- Rich, anybody want a peanut?

View frank's profile


1492 posts in 4440 days

#3 posted 08-05-2008 01:08 PM

Hello Ads; other point that one must understand about epoxy and the using of the West System, is what can be called….’chemically linking’.

When one is doing an-other layer on top of a previous layer, in order to get a good ’bond’, by ’chemical linking’ there is the need to know what stage of the cure process one is working in or through.

Let me add that there are 4-stages of cure that I have noticed with this product; what I call ’liquid time’....’gel time’....’final cure’ and ’full cure’. One should not do any-thing duringliquid time’.

Duringgel timeone can apply a second coat if you are sure you are within the window of gel timecure….and what this means is that one will not have to do any surface preparation, such as sanding to get a ’chemical link’ of the multi-layers.

NOTE: This would not relieve those ’stress cracks’ though that you are concerned about….and actually I have never had the ‘stress cracks’ so I’m wondering if your mixing ratio is accurate. I have found that one needs to be very accurate as to the rules stated by the manufacture when it comes to working with these kinds of epoxies. I believe if I remember correctly, that the manufacture of the West System epoxies also states on their directions that one is not to use this product within a ’confined space’, so you might want to re-read the instructions.

When the epoxy has entered into ’final cure’, one needs to wait for all curing to be done. After the epoxy has reachedfull cure’, one will need to nowprepare’ and ’sandthe previous coat//layer of epoxy to get a properchemical link’.

Hope this helps you some….and,
Thank you.

-- --frank, NH,

View NY_Rocking_Chairs's profile


527 posts in 3831 days

#4 posted 08-05-2008 01:15 PM


Very good points.

I am using the MFG supplied dispensers that one pump of each gives the correct amounts.

As far as the times goes, there are articles that say you have a window from 8 to 12 hours during which you can apply the next layer. Once you get into the final cure stage the epoxy releases a waxy layer which must be sanded off to get a good chemical bond between layers. This varies with temperature, humidity, etc. I suggest you check out West System’s web site, they have a very good article about the use and application of the epoxy. It should answer alot of your questions.

Since this is just filler though you are not relying on strength and may not care about having great chemical bonding.

Sorry I reiterated some of Frank’s comments.

-- Rich, anybody want a peanut?

View tenontim's profile


2131 posts in 3978 days

#5 posted 08-05-2008 02:28 PM

if you’ve ever looked at the mesquite furniture that’s being made, it’s about 10% epoxy, due to all of the knots and voids in it. The guys making this furniture will either use colored epoxy or now they are starting to use a filler with the epoxy, like silver and gold flakes, turquoise chips,etc.

View Ads's profile


15 posts in 3873 days

#6 posted 08-05-2008 04:16 PM

Thanks to everyone who has responded thus far! I’ll be doing a test piece this morning to see what happens. Much of the West Systems material on the web site seems to treat the epoxy more like a structural element, and when using it for a knot or for fairing, they recommend different kinds of fillers. I’ll be sure to come back with my results.

Thanks again!

View SCOTSMAN's profile


5849 posts in 3819 days

#7 posted 08-05-2008 10:28 PM

I think you can even mix it ” VERY CAREFULLY” with old toner from a printer catridge this makes a beautiful black coloured ebony like filler which comes up beautiful when finished try it on a small piece first though to be sure .I have seen it and it looks really nice done in this of luck Alistair p s wear old clothes

-- excuse my typing as I have a form of parkinsons disease

View edp's profile


109 posts in 4194 days

#8 posted 08-06-2008 03:56 PM

I fill knots and voids frequently rather than cut them out. I think they add character. I use an epoxy system referred to as “Pour On” (forget who makes it). For holes that go clear through, I just tape the backside and drop in some wood chips before I fill it. The process is pretty easy though, just mix equal parts of the 2 components, fill the hole and set it aside for a day. Sand it flush and you are good to go.


-- Come on in, the beer is cold and the wood is dry.

View Grumpy's profile


24808 posts in 4085 days

#9 posted 08-07-2008 12:48 AM

There is a two pack epoxy that is a self leveller, poured on not brushed. Have not used mine yet but it could be worth a try.

-- Grumpy - "Always look on the bright side of life"- Monty Python

View MattH's profile


27 posts in 3872 days

#10 posted 08-07-2008 08:15 AM

I’ve done this and it works – I use both West System and System Three. The System Three clear stuff is what I use to fill the pores on the guitars I make, and I have coated other things with West System. When I coat with West System, I thin it with alcohol first and use several coats….

The toner trick is cool. I’ve used lampblack, which is much the same thing. Fresco powders work great, too – and they allow you to color stuff. If you want to mix up a batch of color first, use an egg white as the medium; once you get the color mix right, you’ll have an idea how to do it when you’re working with epoxy (on limited open time).

-- Death before dishonour; nothing before coffee

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