Mixing Epoxy - There must be an easier way!

Discussion in 'Fiberglass and Composite Boat Building' started by hardcoreducknut, Apr 23, 2013.

  1. hardcoreducknut
    Joined: Aug 2011
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    hardcoreducknut Junior Member

    So I've been searching for a better way to mix epoxy. After I finished my last build, my wrist hadn't been that sore since I was 15 years old. :D

    I used tongue depressors, putty knives, etc all by hand. I thought of a drill with a paddle bit, but was nervous about possibly adding air.

    Suggestions?
     
  2. pauloman
    Joined: Jun 2010
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    pauloman Epoxy Vendor

    they do make several different drill based mixers. Also variable speed drills! Worst part is cleaning off the mixer!

    paul - progressive epoxy polymers inc.
     
  3. idkfa
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    idkfa Senior Member

  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    How much epoxy are you mixing at once? I never mix in a pot or cup, but put both parts into a wide. long and flat mixing tray. I use a cake carrier, found at a discount department store. It has wide radius corners, a dead flat bottom, without grooves or bumps and being plastic, cured resin pops right out. With both parts in the tray, I elevate one end slightly, enough to let both parts pool at one end. I use a plastic applicator to drag the goo from the pool end, across the bottom, up hill toward the other end. The flat bottom and well rounded corners allow me to scrape the sides easily and the epoxy is always trying to run back down hill during the mixing process. I've found this solves a few issues. First is exotherm is eliminated to a great degree, because it's spread out over a wide area, in a thin film, it produces far fewer bubbles, it's easy to add fillers directly to the goo and it acts as a container that can be brought to the work, being wide and flat. This tray measures about 12"x18" and is about 4" deep. If mixing larger quantities, a power mixer is possible though run it slowly to avoid bubbles.
     
  5. hardcoreducknut
    Joined: Aug 2011
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    hardcoreducknut Junior Member

    The amounts I mix vary based on what I'm doing. My fillets tend to be rather lengthy, so there are times I might mix a quart, but then add wood flour and it begins to get rather tiresome. Then I have to mix another two or three right after in succession. It really depends on what stage I'm in.

    I never thought about a cake carrier. Makes perfect sense. The rounded corners make it easy to get a nice thorough mix. Maybe I'll go get a cheap hand mixer and try it.
     
  6. Pylasteki
    Joined: Apr 2008
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    Pylasteki Junior Member

    Fold in the dust, don't stir... Pull the goo up into the dust, and push the dust down into the goo.

    Less than 3 ounces, 6 ounce cup... tongue depressor or little black west systems sticks.

    Less than 16 ounces, 1 quart bucket and a paint stick.

    More than 16 ounces, but less than what you can measure in a 5 quart bucket... mix the resin in the 1 quart buckets and put it in the 5 quart.

    2.5 quarts are nice, but they are top heavy and akward for paint work... Use paint mixing paddles. How many sheets of marine plywood have been cut down to size for use as paint paddles and mud hawks?

    If you are trying to mix glue by the quart, put two hand fulls of milled glass fiber or milled cotton fiber in the mix first before adding the cabosil as its easier to get it started thick before making it thicker. Cabosil won't fold in without a fuss unless the stuff is fairly thick from the get go.

    If you are mixing fairing compound, don't. If you are at wholesale, its not cost effective to buy the dust and stir it up, and have to wash the amine blush off. If you are using cheaper epoxy, its less of a wash (particularly if it doesn't blush.) The labor is insane if you figure what it takes to mix a gallon, and what ends up on the floor or blown out the door in the wind.

    After the third or fourth 25lb box of 3M glass bubbles and bags of cabosil, its worth running the figures down to the dollar to find out what you are really saving over buying a 2 part system like Awlgrips Awlfair or Alexseal or Proset (if a little thin). System 3's quick fair is a little quick for production work of size...

    The added benefit of a 2 part putty is you don't have to spend the labor picking trash and wood shavings out of the epoxy, so you don't get the lines and grooves in it as you pull it when someone doesn't close the lid of a 25lb box. At 5:00 the 2 part putty is still mixed the same consistency and doesn't have a quick batch that runs off the side of the boat to sand the next day either. (Fire em...)

    If they get trash in a pail of putty, fire them... but at least you can scrape the stuff off the top. Trying to pick saw dust out of a box of glass bubbles is tough as its light you can't run it through the screen very well... Its like trying to winnow smoke. :D

    The only one I can't stand... Adtech's 2 part epoxy fairing compound as it has no flexibility in low temperature rating and the two parts are darn near the same color from the start. I like the rest of the Adtech line but that one is undeserving...
     
  7. troy2000
    Joined: Nov 2009
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    troy2000 Senior Member

    The flat tray makes perfect sense to me. Reminds me of the way I learned to mix concrete by hand in a mortar box or wheelbarrow, back when Moby Dick was a minnow and I was a kid. We dumped the Portland cement, sand and gravel into a pile, added about 2/3d's as much water as we thought we'd need, and started mixing. First we used the hoe to chop pieces off the near side of the pile and pull them to us. When the pile was all at our end we started pushing it back to the other end, starting at the top of the pile and scraping off a layer at a time. Then we chopped into the near side of the pile and pulled it to us again, shoved it back by scraping off the top again.... and did a 'rinse and repeat' until everything was thoroughly mixed, adding more water as needed.
     
  8. pauloman
    Joined: Jun 2010
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    pauloman Epoxy Vendor

    yes a cheap cake mixer for $10-$20 bucks should work fine - Might even use 1 'spinner' instead of the two it comes with. Store the spinners in a jar filled with TA 661 and you wouldn't even have to clean off the mixed epoxy that is on them.

    paul - progressive epoxy polymers inc
     
  9. hardcoreducknut
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    hardcoreducknut Junior Member

    I'm not sure what you mean by spinner. Is it similar to a wire whisk for scrambling eggs?
     
  10. Ike
    Joined: Apr 2006
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    Ike Senior Member

    Like you I got tired of mixing epoxy by hand, and so i tried different things, but as you said I got a lot of air mixed in. But I finally found a technique that works, but is probably unorthodox. I chuck a 3/16" allen wrench in a drill. I use an extra long allen wrench. I insert it into the epoxy and then turn it on at very slow rpms. Of course the drill is a variable speed drill that will run very slowly. This mixes it well and does not draw air into the epoxy. I typically use small batches and this works well. I have not tried it with large batches.

    PS: make sure you turn the drill off before you pull it out of the epoxy. Otherwise you pull air into the mixture.
     
  11. Herman
    Joined: Oct 2004
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    Herman Senior Member

    There are plenty of mixers which do not draw air into the mix. For instance look at cowles blades

    [​IMG]

    We are having them made relatively cheaply and simple.
     
  12. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    Hmm...nice mixing blade
     
  13. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    There must be something wrong with the mixing technique or bucket fulls of goo.. IMHO
     
  14. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    All mixing techniques force air into the goo. Of course, some are much better then others. Blades that remain below the surface of the goo, can only mix in air clinging to the exposed surface area within the container. The real key to mixing the least amount of air is two fold, a very small amount of surface area exposed, which in itself causes other issues, besides practicality and the other is mixing blade speed. The reason, my technique works so well, is the speed at which I mix, which is less then one stroke per second. If you use a power mixer, set the speed as low and physically practical and just live with the extra few minutes this requires to mix properly.
     

  15. robwilk37
    Joined: Nov 2010
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    robwilk37 Senior Member

    whatever method you use, try to fit the largest handle possibly. gripping with your whole hand is much less fatiguing than just your finger tips. i have made removable handles for all my mixing sticks and squeegees, even the disposable kind that do get reused a few time before tossing. wooden cloths rod split in half and a couple of wood screws is all it takes. try it, it helps. also, learn to mix with both hands, doubles the number of batches you can make before tiring. my .02
     
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