epoxy in knot swelled

[Julio Vargas]

Hi, I filled a knot in a walnut top with total boat epoxy. I waited about a week and then put a coat of boiled linseed oil and then it sat in my shop for a couple of months. I went to take a look at it last night and the epoxy in the knot swelled a bit.

I'd like to proceed with a coat of shellac and then em8000 from target coating.

Any idea why the epoxy swelled? Should I worry about it happening again? I have included a pic but I am sure its hard to see.



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[Michael Schuch]

Maybe the board shrunk do to seasonal variations? Maybe the shrunken knot hole made the epoxy bulge even though the epoxy didn't change in size at all?

Just tossing out the possibility for further discussion, not saying this is what actually happened.

[Julio Vargas]

Maybe the board shrunk do to seasonal variations? Maybe the shrunken knot hole made the epoxy bulge even though the epoxy didn't change in size at all?

Just tossing out the possibility for further discussion, not saying this is what actually happened.

I think you're onto something. I put the epoxy in the knot in early spring when humidity was low. Now we're in the throes of Summer and it's super humid.

Does that mean I shouldn't sand it down? If this theory is correct and I send it down, it will have a void when the knot goes back to its original size.

[Ronald Blue]

From the little research I did linseed oil acts as a drying agent. If I read it correctly. So maybe it caused the wood to shrink. Also is the epoxy still hard and solid? Some products will react with it. Alchohol for one.

[Richard Coers]

Wood swells in the spring and summer, so the knot hole should have gotten wider. How thick was the pour? Deep pores take days to cure and it may not have been fully cured when you sanded it.

[Michael Schuch]

I haven't used boat epoxy but the epoxies that I have used have been very stabile as far as keeping its size. That is why I suggested it might be the wood instead of the epoxy.

I don't know what to advise you as far as sanding it down.

[Prashun Patel]

The wood moved. Even if the shrink happened in the winter, the epoxy may not settle back when the wood later expands. Also it is possible the slab was not dry when the epoxy went in.

It happened to me as well. If you sand it you will have to sand the wood and refinish as well. I left mine.

[Dave Sabo]

Looks like it wasn’t mixed thoroughly. It’s difficult to tell from the pic, looks more like it shrunk which is typical during curing.

But not afterward, neither is expansion. Your wood moved.

[Frank Pratt]

The wood shrunk. I've never heard of epoxy swelling. Agree with insufficient mixing. Did it all cure solid?

[Julio Vargas]

I think you guys are correct, I don't think I mixed the epoxy well or I didn't have the correct ratio...I did something incorrectly because I just went out and stuck my nail in it and it is not as hard as the other knots that I filled around the same time.

This was my first time mixing and using epoxy so lesson learned.

Question is what do I do now? Should I try to dig it out the soft epoxy and put another layer of properly mixed epoxy on top?

[Ronald Blue]

I think you guys are correct, I don't think I mixed the epoxy well or I didn't have the correct ratio...I did something incorrectly because I just went out and stuck my nail in it and it is not as hard as the other knots that I filled around the same time.

This was my first time mixing and using epoxy so lesson learned.

Question is what do I do now? Should I try to dig it out the soft epoxy and put another layer of properly mixed epoxy on top?

Alcohol will soften it. Whether it will be enough to remove I don't know. For those unfamiliar Total Boat is a brand of epoxy. They do obviously make resins for marine use but also for other applications. Jess Crow Makerpoxy is one of their epoxy products intended for uses like this. Just curious what one you used Julio. As the Makerpoxy is 1:1 ratio and pretty simple.

[Julio Vargas]

Alcohol will soften it. Whether it will be enough to remove I don't know. For those unfamiliar Total Boat is a brand of epoxy. They do obviously make resins for marine use but also for other applications. Jess Crow Makerpoxy is one of their epoxy products intended for uses like this. Just curious what one you used Julio. As the Makerpoxy is 1:1 ratio and pretty simple.

I used total boat high performance with their fast hardener.

All the other knots I filled are good, its just this one. I probably either made a mistake in the ratio for this particular knot or I didn't mix the epoxy and hardener enough for this particular knot.

I filled a bunch of knots over period of two days so I was mixing up different batches.

[johnny means]

I try not to just fill through knots with epoxy. They never stay flat. I usually rout out the underside of the knot, leaving less than 1/4" of thickness. I then patch it with a matching piece of regular grain material. The resulting veneer of a knot is much less prone to issues related to seasonal movement and the amount of movement is greatly diminished.

[Maurice Mcmurry]

My guess is that the Knott "took up" the linseed oil and expanded enough to squeeze the epoxy. Trying to get some data on this theory could be fun. If the epoxy remained soft something went wrong with the glue. I use a carefully placed low watt incandescent light bulb to warm up epoxy that is curing too slow. Epoxy can go bad. Proper mixing and ratio are important.

The board shrinking is a very real possibility.

[Ronald Blue]

I used total boat high performance with their fast hardener.

All the other knots I filled are good, its just this one. I probably either made a mistake in the ratio for this particular knot or I didn't mix the epoxy and hardener enough for this particular knot.

I filled a bunch of knots over period of two days so I was mixing up different batches.

As I recall when using the Makerpoxy they said to mix for a minimum of 4 minutes. Mix by hand and not with any sort of power tool. That keeps any air infusion to a minimum. If you do much with epoxy then I recommend getting silicon mixing cups. When it dries you can then flex them and the epoxy will come loose.