Mixing epoxy

I am getting ready for my first build (waiting for the kit getting shipped), and while I am waiting I am trying to put all tools and materials together.

I wonder, what do you guys use to mix epoxy?

Also, please recommend a random orbital sander. (The ones recommended on the CLC website are not produced anymore.)

Thank you!



8 replies:

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RE: Mixing epoxy

Which kit?

My experiece as a n00b:

Mixing epoxy: lots of yaourt contrainers and paint sticks looted while buying paint at the big orange box.

Borrow someone's 6in velcro disc sander, it's not something that you need often. 

Look into two sets of sawhorses. Search this forum. Crucial and cheap for build height.

A clean well-ventilated environment with the correct temp. for epoxy curing is crucial.

RE: Mixing epoxy

as a start, my epoxy batch making has been for kayaks and an annapolis wherry....not larger boats.

for mixing epoxy i use craft sticks.   i use 1 inch X 8 inch craft sticks (e.g., popsicle sticks) like described in this link (not an endorsement of a product) https://www.amazon.com/Natural-Sticks-Length-Finish-Depressors/dp/B07GR27RY3/ref=sr_1_11?dchild=1&keywords=Large+Popsicle+Sticks+8+inch&qid=1606796668&sr=8-11.  if you have a craft store near by, you will probably find them there as well.   you can also use 6 inch x 3/4 inch sticks.  the sticks are so inexpensive i usually keep three sizes around - the jumbo, the large and classic ones.....and i match it with the batch size i am making.  these sticks can also be used for filleting.

for containers, i use diposable plastic cups (the same material as a SOLO cup)...that i buy from my local grocery store.    i buy 16 oz for big batches like this cup  (not an endorsement) https://www.amazon.com/Amazon-Brand-Solimo-Disposable-Plastic/dp/B07BKLH8V9/ref=sxin_11_pb?cv_ct_cx=plastic+cups&dchild=1&keywords=plastic+cups&pd_rd_i=B07BKLH8V9&pd_rd_r=40b0f0c2-a9b3-4b2e-975e-f56ee089a623&pd_rd_w=nelvB&pd_rd_wg=ouYDW&pf_rd_p=ffb450f7-bfad-4e7e-95e8-f2bd147e99a4&pf_rd_r=FZ8ZVVZENZH1WCE74XHR&qid=1606797290&sr=1-2-8065ff8c-2587-4a7f-b8da-1df8b2563c11   

and i also get a package of 9 oz cups for smaller batches.

for whatever its worth, over the years i found that these inexpensive materials worked well and becuase it was inexpensive, i did not try to make batches bigger than they should be becuase i was trying to save expensive mixing sticks and containers.   so the work got better and the costs went down too.

on the random orbital sander (ROS), Dewalt makes good stuff and the price is not bad. the one i have is very similar to this https://www.amazon.com/DEWALT-Random-Sander-5-Inch-DWE6421/dp/B014QUP28E/ref=sr_1_1?crid=2GDWXYH57RNOR&dchild=1&keywords=dewalt+ros+sander&qid=1606798157&sprefix=dewalt+ros%2Chpc%2C144&sr=8-1    there are other good products so i am just trying to give you an indicative sense of what will work. 

but the most important investment i made was to get a hose that attached my ROS sander to my shop vacume to keep the sanding dust out of the air.  it will also make your ROS sander last longer when you use it with a vacume becuase it will keep the dust off the machinery.   it will also keep the dust off of you and your workshop....which is good for your health....even though a good 3m respirator is a workshop essential even with a vacume.

also, buy your sandpaper for your ROS in bulk....if you shop around you can get really good deals.


RE: Mixing epoxy

   Wash and save yogurt cups, cottage cheese containers, takeout bowls, etc.  Small ones and big ones.  Soon you won't have to go buy any more paint cups from the Home Despot. I reuse paint sticks for big batches, tongue depressors for little.  A swipe with a paper towel gets most of the goo off afterwards and I reuse them.  

For mixing, if it's warmer, like above 65F, the resin is less viscous, stirs easier, and the air bubbles leave it better, but i used the MAS system with slow hardener down to about 50F with slightly longer cure times.  My technique is to avoid stirring like I'm making scrambled eggs because that entrains more air.  More like stirring a pot of soup.  And stir continuously for a minute or more before adding filler a little at a time so you don't get one big clump that doesn't break up smoothly.  

I used a DeWalt ROS on the Kaholo I made last year because there is a lot of flat panel area on it.  For the Skerry and Sassafras I've made, there's less flat area, so the ROS got less work and sanding blocks, foam and rigid, got more.  Use a plane or rasp for rounding and smoothing when possible because the shavings go on the floor, not the air like sanding.  And keep your vacuum handy, with a HEPA filter in it, to reduce the dust, especially when sanding and vacuuming epoxy.  You should have your own respirator on then, but the shop will be a lot neater as well.  I hand sand with sanding block in one hand and vacuum hose in the other.  Buy sandpaper in bulk and change it more often than you think you should.

RE: Mixing epoxy

I'm a solo-cup (or generic equivalent) guy too. But avoid the ones with ribbed or textured sides- it's fairly important, especially with small batches, that all of each component is mixed with the other component, not left behind clinging to the sides, hiding from the mixing action of your stir stick.

To go along with the solo cups, I take a gallon size stir stick and cut off a couple inches from the bottom so it isn't heavy enough to topple the cup. I like square-ended stir sticks for getting into the corners of the cup. I think a paint stir stick has about the right strength for mixing thick fairing bog, too -although I've broken a couple. That's maybe more of a bigger boat issue than for kayaks...

My end-of-epoxying-session routine always includes a (paper) shop rag and some denatured alcohol, to clean my squeegies, work area, maybe the boat, and the stir stick.

RE: Mixing epoxy

On our PMD build, my son (the chief boatwright--I am more of a boatwrong) bought a bunch of clear, round deli containers from a restaurant supply place--you know, like they'd put a pound of pototato salad in.  Since they were all exactly the same, we took one of 'em and carefully marked it up with graduations by pouring in measured amounts of water.  We used that as a "master" to mark off the appropriate levels of resin and hardener for mixing the each batch as needed.  Helped us double check that we didn't miscount or otherwise screw up the proportions by counting the strokes on the pumps only.


RE: Mixing epoxy

   Thank you for you responses, guys, very helpful. The kit is for Eastport Pram—since it's my first build, and I am not particulalrly handy, I decided to start with something small.

I got a few mixing cups from CLC. One can reuse micing containers, right? The don't need to be disposable.

Mummichog, good to hear that MAS with slow hardener worked in 50-ish degrees. Temperature is my concern for exposy work (I am in Boston, and maintaining 70 could be challenging).

RE: Mixing epoxy

   You know you are a boat builder when you go to a grocery store and buy the brands that come in suitable mixing containers! LOL


I use Publix Grocery brand yogurt containers a lot. I'll pour the amount of water = to the epoxy resin in the container, make a mark with a sharpie, then add the amount of water= to the proper amount of hardener (1-1,2-1,3-1, etc) then another mark. Dry out the container, then use it...resin to the first line, hardener to the second

You can have several marked ahead of time for multiple batches

I also use teaspoons for measuring smaller batches.

Whenever you go to Lowes, Home Depot, etc, just ask for stirring sticks, they will always give you a couple

RE: Mixing epoxy

>> I got a few mixing cups from CLC. One can reuse micing containers, right? The don't need to be disposable. <<

Within limits. You'll be flexing the mixing container to break off the hardened epoxy inside (and outside.) After enough flexing, or if it's a difficult one, the container will break. Also, after you've mixed up a batch of epoxy thickened with wood filler, there's no way you're going to use the same container for your finish topcoats of epoxy. You just can't get those bad boys spotless.

>> good to hear that MAS with slow hardener worked in 50-ish degrees. Temperature is my concern for exposy work (I am in Boston, and maintaining 70 could be challenging). <<

MAS used to have a temperature/cure time table on their FAQ for low viscosity epoxy. This summer they "improved" their website and got rid of it. The table had cure times down to 41º. It had a little "Not recommended" asterisk next to Slow Hardener at 50º and 41º. At 50º it would film over in 15 hours and be fully cured in 15 days.

My build, taking place near DC, is in an officially unheated garage. In the winter time I switch from slow to medium or fast hardener depending on how cold it is. Both of those are rated down to 41º. You can buy the hardener in pints and quarts so you won't be stuck with a bunch of hardener that you don't want to use in the summer.

I also got a couple of cheap hardware store electric space heaters. They manage to keep my garage about 10º above the outside temp. That means there are still days when I don't epoxy, but lots fewer. YMMV, of course.


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