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CA glue for filling knots/cracks

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Forum topic by Jack_Isidore posted 1218 days ago 5158 views 0 times favorited 18 replies Add to Favorites Watch
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Jack_Isidore

89 posts in 1454 days


1218 days ago

Topic tags/keywords: question ca glue walnut glue knot filler cyanoacrylates

I was taught a method of filling knots and tearout with a CA glue and sawdust mixture. This method entailed mixing the sawdust with the CA glue on a separate surface, and then filling this paste into the knot which had been masked off from the rest of the wood. After a few minutes you remove the masking tape and then in a few more minutes it’s ready to be sanded flat.

I picked up some of the Super T from Woodcraft, which is what they recommended for gap filling, since I couldn’t remember or find the stuff I was taught with. When I went to mix it with the sawdust, it hardened too quickly to apply it in the crack. He (Woodcraft employee) told me that I should have some sawdust in the crack, then put CA glue directly on it, and maybe top off with some more sawdust. He also said I shouldn’t have to mask the area off, getting it on the surface and having a spot that won’t take the finish right hasn’t ever been a problem for him.

I’ve found advise from Woodcraft staff to be hit or miss, so can I get some opinions from y’all? This is on walnut, and I also have Titebond III I could try mixing with some sawdust if that might work just as well.


18 replies so far

View Sawkerf's profile

Sawkerf

1730 posts in 1669 days


#1 posted 1218 days ago

Sounds like that Super T has a very short “set time”, so the salesperson’s suggestion is probably right.

Your TBIII and sawdust should work, too – but it won’t make the defects invisible.

I don’t think that I would ever mask around a filler. I fill proud of the surface and sand flush trying for the best “blend-in” possible. I wouldn’t want to have to deal with an “edge” from the tape.

-- Adversity doesn't build character...................it reveals it.

View WibblyPig's profile

WibblyPig

168 posts in 1875 days


#2 posted 1218 days ago

Use hide glue instead – it’s stainable (if you’re prone to staining) and is an overall joy to work with.

-- Steve, Webster Groves, MO "A society grows great when old men plant trees whose shade they know they shall never sit in."

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Jack_Isidore

89 posts in 1454 days


#3 posted 1218 days ago

Well, despite the masking, I would still get the mixture high enough up that it gets sanded flat. I think the point is to keep it from embedding intself into the wood surrounding the knot, and being noticeable when the wood is finished.

I won’t be staining the project, just finishing with deft danish oil.

I don’t think the point is to make them invisible, so much as just flat and flush.

View Jim Jakosh's profile

Jim Jakosh

11072 posts in 1706 days


#4 posted 1218 days ago

I have found the best way to do that was with 5 minute epoxy and sawdust, copper filings, turquoise, or brass filings. I usually do this with turnings. I turn the part to just about the last cut, overfill the area to make it stick above the surface. then I take the last finish cut and sand and it and it blends in nicely.

For flat work, the tape is a good idea to keep it from bleeding into the surrounding. But I would leave stock on the surface to be planed or sanded off so you can make the repair exactly at the level of the work and not have any surrounding wood with discoloration from the epoxy…...........Jim

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

View woodworkerscott's profile

woodworkerscott

357 posts in 1415 days


#5 posted 1218 days ago

I have heard from several inlay people that CA glue can stain and they recommend masking-off the area around it. I will be doing inlay in a few weeks and will be using CA glue. I am going to mask it off just to be safe.

-- " 'woodworker'.....it's a good word, an honest word." - Sam Maloof

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Jack_Isidore

89 posts in 1454 days


#6 posted 1218 days ago

I think I’ll give some 5 minute epoxy a shot, I have some around here somewhere.

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Jack_Isidore

89 posts in 1454 days


#7 posted 1218 days ago

The only downside to using the Titebond is that I might have to wait hours or even a full day before I can sand it flush. If I can use CA glue or some sort of an epoxy, then I could potentially have the gap filled and sanded flat in a matter of minutes.

View Todd A. Clippinger's profile

Todd A. Clippinger

8717 posts in 2700 days


#8 posted 1218 days ago

I use 1 and 5 minute epoxy all the time for knot holes or voids to be filled. If it is a large enough void I add sawdust.

I would use alternate filling materials as Jim Jakosh does (which looks fantastic when you do this) but my projects have called for me only to use the dust from the board.

-- Todd A. Clippinger, Montana, http://americancraftsmanworkshop.com

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Todd A. Clippinger

8717 posts in 2700 days


#9 posted 1218 days ago

Forgot to mention – I also have used CA glue which I keep on hand all the time. You have to move pretty fast with it. I may or may not mask the area depending on how much milling will follow the void filling procedure.

-- Todd A. Clippinger, Montana, http://americancraftsmanworkshop.com

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Jack_Isidore

89 posts in 1454 days


#10 posted 1218 days ago

Thanks for the info Todd. I think I’ll give epoxy a shot, I would rather be able to take my time, but not have to wait all day either.

Do you use translucent or transparent epoxy? It seems to me that translucent would work blend in better, although if I’m using sawdust mixed in, which I am planning on, maybe it wouldn’t make much of a difference in the end.

View woodworkerscott's profile

woodworkerscott

357 posts in 1415 days


#11 posted 1218 days ago

I use transparent 5 minute, with the sawdust. That way any small unfilled void can be gone over again with just the epoxy and it blends fine.

-- " 'woodworker'.....it's a good word, an honest word." - Sam Maloof

View Todd A. Clippinger's profile

Todd A. Clippinger

8717 posts in 2700 days


#12 posted 1217 days ago

I just use transparent epoxy from Lowe’s & Home Depot.

As a pro I do it all the time and I am looking to get it done fast so I use 5 min and mix it hot or use 1 min.

I like the injector with mixing nozzle package from Lowe’s because I can shoot it accurately into the void. The nozzle has an insert that automatically mixes parts A & B so I don’t have to do it with a stick and smear it into the void, I just inject it.

-- Todd A. Clippinger, Montana, http://americancraftsmanworkshop.com

View 870pilot's profile

870pilot

56 posts in 1369 days


#13 posted 1216 days ago

todd,

i attempted to mix fine sawdust (padauak) with elmers, expoxy and CA (not at the same time) as a decorative touch in drilled holes and router splines. in each instance the rich color of the padauak darkened considerably. in this case, i wanted the color of the fill to be as bright as the pad wood. any suggestions?

-- Olivia's Papa, Newbie Woodworker, Old Tool Fan

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LeviStarkey

15 posts in 1219 days


#14 posted 1216 days ago

use should use an epoxy but if you want to use CA (super) glue. mix it in the taped off area.

View Jack_Isidore's profile

Jack_Isidore

89 posts in 1454 days


#15 posted 1216 days ago

I ran a few test pieces. With the epoxy (typical 5 minute work life, yellow translucent), mixed with walnut sawdust. I did two test areas, with and without masking tape. One of the areas turned cloudy when sanded down. Granted, I didn’t wait for the full 24 hour cure period, and the cloudy area could have just not be solid enough. Either way, I’d prefer to avoid any issues like that—having to wait 20 minutes instead of 15, or having to wait a full 24 hours. I had the same experience when I sanded down the TBIII and sawdust trials, they seems much too light and milky compared to the knots, and my experience with the CA method that looks dark and more natural (I think).

I tried an area that I masked off, filled with sawdust, and dropped CA on top. If it seemed like it wasn’t seeping into the void, I put sawdust on top and pressed it down after a minute or so. This seemed to work well for me, and after sanding and danish oil (which is the finish I’m using), it looks good. I also tried filling some small gaps on through mortices without the sawdust, and they look pretty natural as well. I guess I was thrown off by having to let it mix itself in the void, as opposed to making a paste and applying that. Maybe I’ll do a full on trial of different epoxies and mixtures, and applications in the future. I have lots of expired epoxy that should be fine for this application from work that I would love to use up.

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