Filling voids with epoxy - how do you mask it off?

[Ian Scofield]

Recently I've been filling some voids with epoxy and I'm still trying to perfect the process. The desired end state is to minimize the epoxy that is outside the void because I don't want it to interfere with the finish I'll be putting on after the fact. I have a couple questions:

1) I've been using clear packing tape, but I don't think this is the best route as the epoxy seems to make it's way underneath. What tape do you use?
2) Do you do just a box around the area, or do you try and use several pieces to try and get as close to the edge and follow it around the void? When using the packing tape, I did this for one and it it completely masked off to the edge, however the epoxy made it's way underneath the intersection of every piece of tape. Ended up making a snowflake of epoxy...
3) For a void that goes all the way through, how do you mask the bottom? I used the clear tape and clamped a board across it, but I guess it wasn't tight enough and it ended up seeping out.

[Jamie Buxton]

I don't mask off the surface surrounding the hole. I just overfill the hole, and sand it down flush after it has cured. The sanding operation removes the epoxy that has overflowed.

I close the bottom of the hole with masking tape. Look carefully to make sure you're closing the entire hole.

[Roger Bull]

I use blue tape and Tyvek tape. Clear tape if I'm out of the other. You really have to rub it to get it to attach well. I always plan on some leakage.
If you fill your voids early in the milling process you will generally be able to plane/sand away epoxy that has seeped into the wood and have a uniform surface for finishing.

[Frederick Skelly]

I use blue tape and just box around it. Then, I rub on a little Johnson Paste Wax on the surface around the void (not in the void -around it on top). The excess epoxy comes off easily. I clean off the wax with either DNA or a light finishing plane.

You might try it on scrap to see if it works for you.
Fred

[glenn bradley]

As Roger pointed out, really burnish the tape at the edge you want to seal well. A fingernail or handle end of a chisel or screwdriver will work well. I don't always use tape preferring the method Jamie mentions. When I do I remove the masking as soon as the epoxy is firm to avoid a battle once it is fully cured.

[Ian Scofield]

Thanks everyone for the replies. I'll switch out my tape to masking or blue tape. Also, I like the idea of filling the void before the wood is milled, however does this do a number on the knives of a jointer or planer?

Also, I'll have to try the paste wax on some scrap to see how well that repels the epoxy.

[Al Launier]

For those situations where I do not want leakage under the masking tape I've found that Frog tape does a better job than the blue masking tape. If the area to be filled is small I'll tape over the small area the use a brad point drill bit & drill through the tape. If not a small area, I'll try to cut through the tape with a sharp pointed utility knife following the outline of the void beneath the tape.

[Roger Bull]

Thanks everyone for the replies. I'll switch out my tape to masking or blue tape. Also, I like the idea of filling the void before the wood is milled, however does this do a number on the knives of a jointer or planer?

No problem with epoxy dulling knives. It is really not that hard. In fact you should be sure it has fully cured before jointing, planing, and sanding. If it gums up sandpaper it's not fully cured. Another benefit of planing after epoxy is that if yours develops an amine blush the planer will remove it.

[Bruce Volden]

I use blue tape and just box around it. Then, I rub on a little Johnson Paste Wax on the surface around the void (not in the void -around it on top). The excess epoxy comes off easily. I clean off the wax with either DNA or a light finishing plane.

You might try it on scrap to see if it works for you.
Fred

The old saying. Wax sticks to everything, but nothing sticks to wax!

Bruce

[Bill Conerly]

For some applications, I pull off the tape right after applying the epoxy, then wipe the surrounding surface with acetone.