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Thread: First time using Epoxy for glue up / assembly - some questions

  1. #1
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    First time using Epoxy for glue up / assembly - some questions

    I'm building a Maple entry door (trad mortise and tenon, frame and solid wood panels) and have decided to use Epoxy for all my glueing purposes (joinery, panel edge joints) after doing some reading both here and on WoodWeb about overall strength as well as temperatures that different glues can withstand in exterior door conditions. I've used TB I, II, and III in the past for most things, but haven't built an exterior door before and decided to go with West Systems 105A and 206A (slow hardener) but am unsure about some of the nitty gritty of working with Epoxy.

    This door is actually going in the clients' sunroom that will be part of a new insulated wall I've built that will be part of the air sealed envelope of the house. It will see direct sun, have different humidities and temperatures on each side and will have weatherstripping, a threshold and a sweep, but see no actual wet weather as it's in a sunroom / greenhouse type room.

    My questions are mainly about what to expect compared to PVA glue.

    - On edge (panel) glue ups (or on shoulders of M&T joints for that matter), how do you efficiently get rid of any squeeze out? I usually use a card scraper / chisel after about an hour or so, before the glue has completely hardened and get as much off as I can, making the final glue line clean up easier and more successful with less torn potential torn wood fibers. What's the process with Epoxy?

    - I've read a bit about how Epoxy is structurally gap filling (to a point) but am unsure exactly how much slop to build into the tenons. I've currently got the rail and stile mortise and tenon joinery done and dry fit, but have cut my tenons as I normally would which is a fit that doesn't need to be struck with a mallet to be fit, but is tight enough to hold the pieces together if I lifted up and suspended the joint in air. I fear this may be too tight for Epoxy and starve the joint, but really don't have practical experience enough to know. What's your rule of thumb for joinery and Epoxy?

    Any tips and words of wisdom regarding using and working with Epoxy in this application? I kind of hate using a clients' project as a learning curve for a new procedure, but sometimes that's the way the cookie crumbles and you adjust accordingly and do the best you can with what you know.

    Thanks for any advice!

    -Phillip
    Last edited by Phillip Mitchell; 09-07-2019 at 9:32 AM.
    That's just like, your opinion, man.

  2. #2
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    Draw-bore it.
    Bumbling forward into the unknown.

  3. #3
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    Especially on a dense hardwood like maple, epoxy relies on a rough surface for adhesion. Saw or sand mating surfaces to no more than 80#.

    Be sure to use resin and hardener in the recommended ratio and mix thoroughly for a full minute, scraping the bottom and sides of the container and the stir stick.

    Pour the mix into a flat pan to extend open time. A large compact mass of epoxy can kick off in a hurry making a hot smelly mess. With West System 105/205 you can get up to an hour of assembly time at 70 F but the material is gradually hardening all the while. You may want to do a couple of smaller mixes or glue up in stages. In hot weather use a slow hardener.

    You can remove excess when wet with vinegar, denatured alcohol or acetone, but you run the risk of wiping the epoxy out of the joint surface and leaving a hollow. I usually remove the bulk with a blunt chisel and leave the rest to cure, then sand. You can mask around the joints with tape or wax. Epoxy can penetrate deeper than other adhesives so you may need to sand the surface more than usual. Once it starts to set up, leave it alone. When the surface can't be dented with a thumbnail the clamps can be removed.

    Epoxy likes to wick into end grain so you may need to apply repeatedly before assembly or use a fiber additive. The wicking can produce a fat looking joint in maple, so do a test before committing.

    You can leave more clearance for the glueline than with pva but it's not necessary. Make sure there is a way for excess glue to escape from the mortises.
    Last edited by Kevin Jenness; 09-07-2019 at 10:00 AM.

  4. #4
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    Quote Originally Posted by Phillip Mitchell View Post
    I'm building a Maple entry door (trad mortise and tenon, frame and solid wood panels) and have decided to use Epoxy for all my glueing purposes (joinery, panel edge joints) after doing some reading both here and on WoodWeb about overall strength as well as temperatures that different glues can withstand in exterior door conditions. I've used TB I, II, and III in the past for most things, but haven't built an exterior door before and decided to go with West Systems 105A and 206A (slow hardener) but am unsure about some of the nitty gritty of working with Epoxy.

    This door is actually going in the clients' sunroom that will be part of a new insulated wall I've built that will be part of the air sealed envelope of the house. It will see direct sun, have different humidities and temperatures on each side and will have weatherstripping, a threshold and a sweep, but see no actual wet weather as it's in a sunroom / greenhouse type room.

    My questions are mainly about what to expect compared to PVA glue.

    - On edge (panel) glue ups (or on shoulders of M&T joints for that matter), how do you efficiently get rid of any squeeze out? I usually use a card scraper / chisel after about an hour or so, before the glue has completely hardened and get as much off as I can, making the final glue line clean up easier and more successful with less torn potential torn wood fibers. What's the process with Epoxy?

    I follow the same process as with PVA glues. The epoxy will get "gummy" after time and can be scraped off. Don't try and get a lot of squeeze out with epoxy.
    Once the epoxy is set, 24 hours, I'll use acetone to clean up any residual. Epoxy will reach ~80+ % of it's cure after 24 hours. It really takes a few days for 100% cure.


    - I've read a bit about how Epoxy is structurally gap filling (to a point) but am unsure exactly how much slop to build into the tenons. I've currently got the rail and stile mortise and tenon joinery done and dry fit, but have cut my tenons as I normally would which is a fit that doesn't need to be struck with a mallet to be fit, but is tight enough to hold the pieces together if I lifted up and suspended the joint in air. I fear this may be too tight for Epoxy and starve the joint, but really don't have practical experience enough to know. What's your rule of thumb for joinery and Epoxy?
    This all depends on the epoxy. Some epoxies are gap filling, they have a thixotropic agent in them to perform this function. Some do not and do rely on a fit as tight as you would have for a PVA glue. If you can push the joint together by hand, without beating it together, I would proceed just as normal. If you have a loose joint, a more "structural" type of epoxy may be better.

    Any tips and words of wisdom regarding using and working with Epoxy in this application? I kind of hate using a clients' project as a learning curve for a new procedure, but sometimes that's the way the cookie crumbles and you adjust accordingly and do the best you can with what you know.

    Thanks for any advice!

    -Phillip
    The benefit to epoxy is longer open/working time,and less clamping pressure. With traditional PVA's you need a lot of clamping pressure. With epoxy you only need enough to bring the joint together in alignment. If your joints are cut well, blue painters tape provides more than enough clamping force for epoxy. With a door, you literally can lay it on the work bench, epoxy the joints together, square the rails, stiles and panels, then tape each joint in place. Come back in 24 hours and size the door. I just got done doing this to two 100 year old doors, that were blown.
    Don't try for super perfect surfaces. the epoxy, as pointed out previously, does like some rough adhesion surfaces.
    When I do epoxy glue ups. I always have some sacrificial material, and make a test joint, out of the material I am working with. I will just put these together with the left over epoxy, and make sure all is well with them the next day.
    Last edited by Mike Cutler; 09-07-2019 at 11:11 AM.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  5. #5
    My couple of adds to what was said above (I agree with it all). If I want more time, I spread epoxy thin into a metal tray and put it on an ice pack (and use slow hardener). The book that is available online or in stores by West System is an excellent reference.

  6. #6
    Be sure to remove squeeze out and runs while the epoxy is still wet or soft. It can be a real beast once it's fully cured.

  7. #7
    I know this sounds nutty, but it worked for me... I paste waxed the parts that I wanted to protect from getting squeeze out on. Not the mating surfaces obviously - the surfaces nearby that I wanted to protect. Then the squeeze out lifted easily with a razor blade. I cleaned the wax off by cleaning the area with denatured alcohol, followed by a couple passes with a smoothing plane. I was working with poplar, so but you might try it on scrap to see if it works for you.
    Fred
    "All that is necessary for the triumph of evil is that good men do nothing."
    - Sir Edmund Burke

  8. #8
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    Don't expect to clean up cured epoxy with acetone.

    Woodworking epoxies are inherently gap-filling- with no solvent they don't shrink when curing and are strong. A poorly fitted joint that has the voids filled with epoxy will be virtually as strong as a good one (not advocating for sloppy joinery, but it can help in repairs) You may need to thicken the mix with colloidal silica to keep it from running out of an open joint, but a mortise and tenon joint doesn't need it. There are thickened products like System 3's Magic Gel and various putties that will stay in place on a vertical surface.

  9. #9
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    I use waxed paper to protect the assembly surface I'm using and especially any clamps onto which the epoxy may run. I use painters tape on all surfaces at joints during a dry test assembly, but inevitably some will run out onto a surface. It does somewhat lubricate the pieces, as opposed to swelling them up like PVA glue, so sometimes uneven clamping will cause the pieces to creep.

  10. #10
    Quote Originally Posted by scott lipscomb View Post
    If I want more time, I spread epoxy thin into a metal tray and put it on an ice pack (and use slow hardener).
    I agree with this. I've put ice cubes in a larger tray and then set my epoxy tray on top of the ice. A large amount of epoxy can get hot from the reaction and harden up quickly. Keeping it cool will give you a lot more time to get your project together. It doesn't affect the final glue outcome.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  11. #11
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    Kevin

    I have used acetone with success, when working with epoxies, for a long time now. 30+ years. That's how we cleaned it up in the boat yard.
    I don't wait for the epoxy to cure, just start to gel up on the surface. Fully cured, you'll have to sand it out.
    Naphtha will work to some extent, and MEK works also, but that is a very bad product to work with.
    You have to be quick and careful. The best advice is to not have squeeze out with epoxy.

  12. #12
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    Quote Originally Posted by Brian Holcombe View Post
    Draw-bore it.
    I wasn't considering that, but now I am. I've draw-bored a few furniture-scale things in the past and was generally pleased with technique. Thanks for the suggestion!
    That's just like, your opinion, man.

  13. #13
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    Happy to help!
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  14. #14
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    For four cedar mortise-and-tenon frame-and-panel gates in direct Sun, epoxy has served very well.

    1) All of the above.

    2) Epoxy softens when warm/hot, such as exposure to direct Sun, whether thixotropic or not. Any slop in your joints will allow the door to sag/rack, so keep your joints tight.

    3) If not a thixotropic formulation, epoxy likes to seep through cracks, loose seams, etc. Assure all is tight and block cracks with masking tape. Don't be surprised by seepage onto finished surfaces.

    --Wayne

  15. #15
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    West System has an epoxy with an open time of nearly an hour. Depending on temperature. You should leave it in clamps for a day or two, though.

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