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Thread: Tricks to using CA glue & coffee grounds to fill voids?

  1. #16
    Join Date
    May 2008
    Location
    Mountain Home, AR
    Posts
    547
    Personally I've had better luck with thin CA and coffee grounds than epoxy and coffee grounds. In my experience the CA not only soaks into the grounds, but also the wood around it, creating a stronger bond. The same solution using epoxy doesn't bond as well with the surrounding wood and I've had more inlaces turn loose when hit with a gouge than I've been able to smooth and finish. Plus, it is much easier to fill tiny cracks with CA than with epoxy - just rub some near-powder coffee grounds (or powdered metal/stone) into the crack and put just enough CA on it to soak in, wait 2 minutes, sand a touch and you're back in business.

    It will soak in and stain wood where you don't want it to so be careful how much you use or seal the piece with shellac/wax/DO/lacquer/etc so it doesn't soak in. Thin CA will cure almost instantly when it meets coffee grounds, so on larger voids I will make a dam around the void with coffee grounds and if the CA runs it will stop and harden as soon as it touches the dam. And if you have some uncured CA sitting on top of your fill you can sprinkle some coffee on it and it will cure instantly.

    I also prefer the more consistent density and appearance of coffee grounds with CA over (untinted) epoxy. It looks more natural to me, but appearance is subjective. In the end you should use what you're familiar with and what works best for you. In all fairness I've only used QuickCure 5-minute epoxy from Lee Valley. The slow-cure stuff may work better, but this is what I have and my experience with it.

    If I think about it tonight I will take some close-ups of some fill jobs I've done and post them up.

  2. #17
    Join Date
    Feb 2008
    Location
    lufkin tx
    Posts
    2,054
    This is probably cutting frog hairs but it is what it is. CA sands like granite .... I have a ship model of basswood and CA that started falling apart at 20 years of age. The book agrees. Ca stains light colored woods and an open void sprayed with a film finish is made to let go. A crack is different. In lab tests all the common glues were essentially the same tensil strengths except for gorilla glue. It was about 1/2 the strength of the other glues. Significantly, only two glues developed good strength without firm clamping of the glue joint. Epoxy and CA need no clamp pressure. Only CA held full strength on wet wood (thank goodness). Water based glue strength is compromised to some degree?? Leo, After using epoxies on boats, cars and turnings (barrels) I find that only overly generous thinning with LT or Ace. or dyes slow down the hardening. Temperature is much more important than other influences. All old boat owners have a gallon can of epoxy.(solid) with a brush sticking out indicating the point when they learned that rising temps or too much volume reacting at once generated ferocious temps which then speeds up the batch. Maybe this is how they discovered "critical mass".

  3. #18
    Join Date
    Jul 2008
    Location
    Atikokan, Rainy River district, Ontario
    Posts
    3,540
    Robert my youngest son is an electrical engineer that works for a company that makes satellite communication equipment, and other special products, I know that they would fasten antenna with Epoxy that had a “short good for lifetime", they would heat the epoxy to IIRC 60 degrees centigrade (140F) to get the epoxy to harden quicker and get a good and consistent hardening, so yes Epoxy is temperature sensitive, and it will harden up very fast if too much is used in one go, as it will accelerate heating itself, DAMHIKT
    Last edited by Leo Van Der Loo; 08-27-2016 at 1:03 AM.
    Have fun and take care

  4. #19
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    12,298

    Thermal runaway

    Quote Originally Posted by Leo Van Der Loo View Post
    ... so yes Epoxy is temperature sensitive, and it will harden up very fast if too much is used in one go, as it will accelerate heating itself, DAMHIKT
    Back in the '70s I ran a small metallography lab, potting sections from neclear reactor elements in epoxy so I could grind and polish. The sample forms held perhaps a cubic inch or so of epoxy. Once I must heated a sample a bit too much before putting it in the vacuum chamber. The reaction was incredible, the thermal "runaway" caused the epoxy to smoke and crack with pops and snaps, turning it a dark burnt brown in seconds once the reaction started. Learned that lesson!

    JKJ

  5. #20
    Quote Originally Posted by Doug Rasmussen View Post
    Correct me if this is wrong, but I've read several places not to use CA where it's to be permanent. Apparently, it has a usable life and will fail after x number of years. .................................................. .................................................. .................................................. ............................
    Okay, I attempted to find articles where I read about the useful life of CA glue joints. One easy find was an article in American Woodturner, 26.4:24, quotes by both David Ellsworth and Richard Raffan. The article concluded with : "If what you are making needs to stand the test of time, be aware that CA glue has not been in use by woodturners for long enough to say with authority that glue joints will last. "

    Realizing those were only opinions not based on extensive testing I did call a CA glue manufacturer (don't recall which one). The tech guy confirmed a joint does have a lifespan, but how long "depends" (whatever that means?).

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