Epoxy 101

Epoxy can be challenging. You’ve got challenges like mix ratios, spilling, mixing, thickening, spilling, pot life, spilling, application, spilling, out-gassing, curing and spilling. And, it is easy to spill epoxy all over everything. If you are in a hurry, epoxy is not for you. Epoxy can be messy and the solvents used for clean-up are carcinogens, can cause cancer and can give you cancer. Here are a few things that I have learned after getting epoxy all over the floor, on my hands, arms, stomach and in my hair.

Update: recent studies conclude that not all solvents are carcinogens. But, they are pollutants. And, more importantly, they are often made by recycling and therefore contain contaminants that will ruin your epoxy. Regardless, there is no need for solvents in epoxy/wood boat building.

No kidding, I somehow got epoxy in my hair! And, last spring, I was lying on my back, in my boat, applying epoxy overhead. Somehow, I got confused which way was up and I dumped the cup of epoxy on my chest. Luckily, I was wearing my epoxy shirt. That’s my old ragged cotton long sleeve T-shirt that I wear when I play with epoxy. That shirt is more epoxy than cotton.

The best way to deal with epoxy on your body is let it cure and peel it off. It doesn’t stick well to skin due to body oils. But that shit sticks great to hair, especially the hair on your chest. Wax treatment for hair removal? Why mess with wax when you can use epoxy?

Before I get too far ahead of myself, there is some great literature out there about using epoxy. The West System User Manual and ProductGuide are awesome. My favorite is System Three’s Epoxy Book. I got my first copy over 20 years ago. I studied it like a college text book and highlighted the important parts. It has cute animations and the author has a sense of humor.

 

Epoxies

I have used both West System and System Three two-part marine epoxies. I love them both. They are both great products with great technical support. They both offer all the must-have accessories like pre-measured dispenser pumps set up to work with any of their containers. If they would add medical marijuana and condoms to their product line, they would be the ultimate epoxy supplier.

I thought I had died and gone to heaven when fat-free bologna was invented. Then I thought I had died and gone to heaven when blush-free epoxy was invented. When I first started working with epoxy over 20 years ago, all epoxies would blush (blush = form a wax on the surface while curing. Nothing sticks to the wax and it must be removed by washing and painful sanding between coats. A sharp stick in the eye is less painful.) But nowadays, blush-free epoxies are available. No more waking up at odd hours of the night to get that next coat of epoxy on before the blush forms. And no more sanding and sanding and sanding and sanding and sanding and sanding and sanding.

I’ll know I’ve died and gone to heaven when they invent edible epoxy. No more waste. Just eat the excess. I would like to formally request that the epoxy chemists make it available in banana and peanut butter flavors.

Alignment of pieces being joined

Plywood scarphs

Nemah bottom panels aligned
for gluing

Lately, I have been building boats with bright finish (bright = natural wood finish). So, I prefer my scarph joints to be just like me, perfect and good-looking. I line the sheets up in the dry and screw them down to the work surface the way I want them to look after gluing. I would insert an inappropriate joke about “lining them up and screwing them down” but I don’t wanna get banned from the internet again. I place the screws near the edges, in the portions of plywood that will become scrap when the final boat panel shapes are cut. 

Completed Nemah scarph

Since the final cut-out boat panels will be smaller than the glued plywood sheets, the plywood sheets do not have to be perfectly aligned.

Once I get them screwed down the way I want them, I unscrew enough of the sheets to apply epoxy, re-screw them to the work surface, leave them alone and drink whiskey until the epoxy cures.

Completed scarph in
Sea Scull RevolutionPly

If you are painting your boat then the appearance of the joint is less important. You can align the joints sloppy. Be sure to use enough epoxy to fill all of the voids in the joint, and enough to overfill the surface voids at the joint. The surface voids can be sanded fair after the epoxy cures.

Don’t be afraid to use too much epoxy. Like Mo ‘Poxy says, “more epoxy means wealthier epoxy company shareholders.”

 

 

 

Sloppy scarph joint in okoume
for painted Chesapeake kayak

 

 

 

 

 

 

 

Stripping Scarphs

Inwales and rubrails lined up
for gluing

Wood strips, like inwhales and rubrails need to be aligned as well as possible since the final length should be straight. I strike a chalk line on my work surface and line up all the pieces to the chalk line. Then I spend the rest of the day washing red chalk off of my hands and everything I touch.


Inwales and rubrails glued and clamped



Completed, unsanded scarph



 

 

 

 

 

Gluing Together

For gluing things together like attaching inwhales to the side panels or building rowing thwarts, I use the same dry-screw method as with plywood scarphs but with one little twist. I screw everything together like I want it, remove enough screws to apply epoxy, screw it back together, leave it alone and drink vodka until the epoxy cures. Did you catch the twist? I use vodka instead of whiskey.

Surface Preparation
The mating surfaces do not have to be perfect. Perfect might actually result in starving the joint of epoxy and violate Mo ‘Poxy rule number 1 “the more epoxy, the stronger the joint.” So, imperfect mates with sufficient epoxy are better than perfect mates. If the entire boat were made of epoxy instead of wood, it would be way stronger than a wood boat. Unfortunately, it would also be way way more expensive and weigh way way way more.

Everything we read about surface preparation before epoxy glue-up says that the mating surfaces must be dust-free. Then the same instructions tell us to add dust to the epoxy to thicken it. Dust free then add dust? WTF? I call bullshit.

Dust on the mating surfaces is OK since you are going to apply unthickened epoxy to the mating surfaces, which will mix the dust up with the unthickened epoxy. Then you are going to apply epoxy thickened with dust (silica powder and wood flour) to glue the surfaces together. Like David Lee Roth said, “I don’t fret the little shit.” (which he follows by saying “It’s all little shit.”) So, the little shit is OK. I’m not advocating that we all throw a handful of dust on each of the mating surfaces before gluing. I vacuum my mating surfaces before gluing but I am not obsessed with dust removal. If I encounter a little dust on the surfaces, I let it be.

Things that chemically inhibit the joint like wax, oil, grease and solvents are notta too good.

I hope blood and sweat are OK, every one of my boats gets at least one unintentional blood donation and several sweat donations.

Being that I have a keen sense of the obvious, I have noticed that things like wood chips, sand, masking tape, wax paper, screws, beer bottle caps and the little plastic toothpicks through the olives in my martinis, will mess up an epoxy joint.

Mosquitoes in epoxy are a good thing. I embed at least one mosquito in every boat I build. It’s my way of showing all of the mosquitoes what happens if you mess with me and my epoxy.

Clothing

Someone once said to me “Anything you say, can, and will, be used against you in the court of law.” Actually, I think I have been told that more than once. The epoxy equivalent is “Anything you expose, can, and will, be covered in epoxy.”

I have an epoxy outfit hanging in my shop - my worthless work boots, my nastiest blue jeans, my long sleeve half-cotton half-epoxy tee shirt, and a bandana. I get epoxy on some article of clothing every time I work with epoxy. And I don’t care. I had a girlfriend tell me that she was leaving me because I was apathetic. I told her, “Go ahead and leave. I don’t care.” I hang the clothes in the shop at the end of the day and the epoxy on the clothes is cured in the morning when I don the clothes again. When I get epoxy on my fingers, I wipe them on my jeans. When I find a brush bristle, twig or wood chip in epoxy, I pick it out with my fingers and just like a booger, I wipe it on my shirt.

Disposable latex gloves – a buy them by the box of 100, I always wear them when playing with epoxy. Tracy O’Brien claims that there is a hand cream that you can use instead of gloves. I tried it once. It spelled disaster. And, get this, I once swallowed a bunch of Scrabble tiles. My next shit spelled disaster.

No need for respiratory protection since epoxy is non-volatile at room temperature. I know from experience that you can huff that shit all day and you won’t get high.

But, don’t ever inhale epoxy mist or fumes unless you wanna die. Mist is created by spray-applying epoxy, like spray paint mist. You know how you want epoxy to form a very reliable permanent coating on your boat? Well, if you inhale epoxy mist, it will form a very reliable permanent coating on your lungs. Goodnight Irene. And fumes, I’ve seen them and probably inhaled a little which is why I have the lung capacity of a 70-year-old man. Fumes occur when you mix a large pot of epoxy and the heat generated by the chemical reaction of the curing epoxy is enough heat to cause the epoxy to evaporate, like boiling. Then epoxy “steam” comes out of the pot and finds its way into your lungs. Always mix small batches of epoxy. Never mix a bucket of epoxy like I did, or it will boil. There is another advantage to small batches - when you mess up and spill tequila into the epoxy, it is not so painful to throw a little bit of the expensive epoxy away.

The Epoxy Center

Old epoxy center

Before building the Lady C, I built the epoxy center. It was a junky cabinet made of scrap plywood that held everything needed for epoxy work: resin, hardener, stir sticks, fillers, brushes, fiberglass tape, fiberglass cloth, wax paper, floor wax, latex gloves, scotch and flavored lubricants. That epoxy center built the Lady C and four CLC Chesapeake mahogany kayaks.

Old epoxy center
in background


When I set up in the new boat shop, I made the end of the work bench into another epoxy center.



New epoxy center
wood flour, silica powder, heater, hardener, resin, mixing comtainers
latex gloves mixing sticks, paper towels

Besides the obvious advantage of having everything in one place, the epoxy center also creates habits in the order of which you do things as in: get out mixing pot, get out mixing stick, one pump hardener, move right and one pump resin, move left and one scoop silica, move left and one scoop wood flour. Any order and direction works, it is the repetition that reduces the likelihood of screwing up a batch.

 

Mixing Epoxy

Containers
Long before you start to build an S&G boat with epoxy, start saving mixing containers. Sure, your family and friends will think you have lost your marbles when they see 27 peanut cans and 46 cottage cheese containers in the drawer. But, in the end, they will understand….maybe.

Tin and aluminum cans are good as long as they don’t have many ridges or lips to hinder mixing. My favorite container is the Blue Diamond Almonds 6 ounce can. The best part is the almonds. After eating the almonds, I use tin snips to remove the lip from the top rim, leaving a very sharp edge to cut myself.

Tin, aluminum and wood are good because, unlike plastic, the epoxy sticks to them. With plastic containers, if you reuse them, the epoxy cured in them from the previous use will flake off leaving chunks in your new batch of epoxy and that sucks. With tin, aluminum and wood, when finished I just swab the container with a paper towel and let the residual epoxy cure in the container. Unthickened epoxy will flow out into a smooth shiny surface in the bottom of the can and not hinder future mixing. Thickened epoxy leaves a rough surface and is not good for future mixing of hardener and resin but can still be used for thickening.

I seldom reuse plastic containers. I use them once and throw them away.

I had a wood salad bowl that cracked because I put it in the dishwasher. Perfect! It became my main epoxy mixing bowl for the construction of the Lady C. Layer after layer of epoxy, some layers unthickened (clear), some thickened with silica (white) some thickened with wood flour (brown) and some thickened with graphite powder (black), built up over time. When I completed the boat, I cut the salad bowl in half and revealed the geologic history of the Lady C.

Warm epoxy

Heater. hardener and resin

What’s better than a cup of warm cocoa after a day of skiing? Well, lots of things, like a cold beer after a day of skiing. Or better yet, a cold beer and a shot of tequila followed by an orgy. But not much beats a cup of warm epoxy after a day of boat building.

I have a little heater beside my jugs of epoxy resin and hardener. A few hours before each therapy session, I mean epoxy session, I turn on the heater. Warm resin and hardener mix easier and saturate fiberglass better.

There is one drawback - the warmer the epoxy, the faster the cure and, therefore, the shorter the pot life. (pot life = the amount of time that a batch of epoxy is usable before it begins to harden in the mixing pot, or, pot life = the life lived by my daughter's boyfriend).  Once epoxy resin and hardener are mixed, the clock starts ticking. The curing of epoxy is a chemical reaction and the rate of the chemical reaction doubles for every 18°F temperature increase. It works in reverse for colder temperatures. So, warm epoxy has a shorter pot life. To avoid wasting epoxy because it hardens in the pot, use several small batches that can be applied quickly rather than one larger batch that can harden in the pot or possibly boil as described above.

And, when in doubt, throw it out. If you are not sure that you got your mix ratio right or not sure if there is a contaminant in the mix, throw the mix away.

Pumps

If your epoxy manufacturer sells pre-measured resin and hardener pumps, BUY THEM. They cost less than a few messed up batches of epoxy and there is nothing worse than trying to remove an uncured layer of epoxy from your dreamboat. Or worse, removing it from or her kayak.

 

Thickening for Gluing

No thickening is necessary for wetting-out fiberglass or coating wood.

To thicken epoxy for gluing, filling or fairing (fairing = blading a tapered layer of thickened epoxy at the edge of a hump such as the edge of fiberglass, to be sanded after curing and hide the hump when the boat is painted, like Bondo on your car fender). After thoroughly mixing resin and hardener, I transfer the mix to my thickening pot, leaving my mixing pot for re-use. Then I add silica powder to thicken the epoxy. I start with a little silica and add until I get the thickness I want. If I want to add wood flour for color, flavor or a sandable fairing, I hold back on the amount of silica.

When using wood flour, the resulting paste looks like peanut butter. When my request for edible, peanut-butter-flavored epoxy is granted, Saltine crackers will take a place beside my resin and hardener jugs.

Epoxy Application and Fiberglass

Epoxy doesn’t stick to wax. That is why instructions for large stitch&glue boats with thick, stiff plywood that require 18 gauge bailing wire for stitches, recommend coating the stitches with wax so they can be pulled after the epoxy cures. I use Johnson Paste Wax which is getting harder and harder to find since, well, what the hell is paste wax anyway?

Epoxy’s dislike of wax means that wax paper can be used to keep epoxy from sticking to shit that you don’t want it sticking to, like your work bench.


Epoxy doesn’t like polyethylene either. That is why I have a layer of polyethylene sheeting (AKA visqueen) on my work surface. I bought a giant roll years ago. I have to reline the work surface every few weeks as the sheeting gets hacked up by tools and has too many globs of spilled/dripped cured epoxy. And, the giant roll of plastic sheeting is great to have around for Friday Night Yogurt Wrestling.



Sea Scull RevolutionPly panels scarphed together.
Note the polyethylene (visqueen) sheeting
on the work surface.

Dry layup of epoxy-saturated fiberglass
on Sea Scull RevolutionPly side panels

When lining a piece of plywood with epoxy-saturated fiberglass, I use the dry method. That is, I refrain from alcohol consumption for at least 8 hours before any epoxy/fiberglass session. And I refrain from alcohol consumption for at least 10 minutes after each epoxy/fiberglass session. I lay the dry fiberglass on the uncoated dry wood surface. Then I dump a cup of unthickened epoxy resin/hardener mix near the middle of the fiberglass. I use a squeegee to spread the epoxy from the middle towards the edges, leaving ample epoxy to saturate the fiberglass and underlying wood. Once saturated, I use the squeegee to squeeze out all bubbles and excess epoxy, pressing the fiberglass to the wood, working from the middle towards the edges, pressing out all humps in the fiberglass. When I run out of epoxy, I mix another cup and continue.

The few times I have not used a squeegee, it left humps in the fiberglass. The fiberglass was still saturated and bonded to the wood with no voids (devoid of voids?) but there was excess epoxy under the fiberglass creating unsightly humps.

I have been using windshield-washing squeegees but epoxy sticks to them so they have a short life. I just received a handful of squeegees from System Three that are made of a material that epoxy does not stick to. I think when you are done you leave the epoxy on them and peel it off after it cures. I’ll find out.

There is a thing called the wet method where you wet the wood surface and/or fiberglass with epoxy before applying the fiberglass. Sounds like a good way to get the fiberglass stuck to all kinds of places that you don’t want it stuck to, like your hair.

Then there was the time I took someone’s advice and pre-coated the plywood panels with epoxy, let it cure, sanded them and dry-applied epoxy-saturated fiberglass. The theory was that the pre-coating would prevent the wood from sucking up the epoxy and starving the fiberglass. I now know what a waste of time that was. I have not pre-coated since. Seven boats later, I have never seen this starving phenomenon.

Sea Scull RevolutionPly panels
with final epoxy layer

After the epoxy is tack-free, I brush on a layer of unthickened epoxy to fill the weave of the fiberglass and leave a showroom finish. For 20 years I have read that applying the epoxy by rolling and tipping-out with foam brushes is the way to go. But I have so many disposable bristle brushes that I refused to use foam brushes. The other day, for the first time, I tried foam brushes, Holy shit!! They work great!! No need to roll, just dump the epoxy on the surface, smear it around with the foam brush then tip-out. It’s a thing of beauty and none of those little-shit brush bristles to keep picking out of the epoxy.

Bear in mind that everything I have talked about in applying epoxy and fiberglass is on a level surface. When you start working on sloped surfaces, the same principles apply but you are challenged to prevent epoxy running, drips and sags. And I don’t care what West System’s web site and brochures say, that 207 hardener runs like no other. I had to turn boats on their side to prevent drips and sags when applying West System epoxy resin with 207 hardener to the side panel of a boat.

Curing
So the curing of epoxy is a chemical reaction and the rate of the reaction can be influenced by temperature. Being the smart-ass that I am, I decided to cool the shop to 50°F to provide longer pot life. Then I applied the epoxy and fiberglass, turned the temperature in the shop up to 80°F and started hitting the bottle. I, am a fooking genius!

The next day I walked into the shop to see the disaster that my genius had created. Two things went wrong.

Number 1) the heater ran all night as intended but it is a fan coil heater and the fan stirred up dust all night. Every speck of dust that landed on the uncured epoxy surface created a tiny stalagmite that looked like shit.

And B) the wood out-gassed. There aren’t too many things on this planet that can out gas me but this piece of plywood sure tried. Out gassing is when the moisture in the wood vaporizes, exits the wood and floats the epoxy-saturated fiberglass off of the plywood, leaving hundreds of tiny bubbles. What causes out-gassing? Beans, beer and heat. The moisture in the wood was quite happy to stay liquid at cool temperatures. When I turned up the heat, the moisture decided to become vapor and leave the wood.

Never again. Nowadays I heat the shop before any epoxy/fiberglass work. When things are toasty warm, I turn off the heater, do my epoxy/fiberglass layup and hit the bottle. The shop continues to cool, with no fan running, as the epoxy cures. Once the epoxy has cured enough to not react to dust and to not allow moisture vapor bubbles, I can turn the heat up as high as I want.

Cleanup

The best way to cleanup epoxy is don’t.

Clothes

Wear clothes that you don’t care about and cover yourself from head to toe. Use disposable latex gloves.

Mixing Containers

Start your family eating lots of Blue Diamond Almonds in the 6 ounce cans two years before building a boat. Use disposable mixing containers. If you keep a container for mixing unthickened epoxy separate from the container for thickening epoxy, you can reuse the containers several times. Swab them out with a paper towel. Set them on wax paper so they don’t get clued to the work bench and let the remaining epoxy cure in the containers. Eventually they will become so goobbered up that you need to throw them away.

Mixing Sticks

Start your family eating lots of popsicles two years before building a boat. Use paper towels to wipe epoxy off of the mixing stick and lay it on wax paper. You can get many uses out of one mixing stick. I used to cut scraps of wood for mixing sticks until I discovered that System Three sells boxes of 500 tongue depressors.

 

Disposable Chip Brushes

Buy them by the box. Use ‘em and lose ‘em

   

Paper Towels

Wipe things down with paper towels.

Puddy Knives

Wipe them with paper towels, let the remaining epoxy cure and sand it off.

Plastic Garbage Cans

Epoxy doesn’t stick to most plastics. If you use plastic garbage cans, your cured-epoxy-covered stuff will fall out of the can when you dump the garbage behind your neighbor’s tool shed.

Solvents

Don’t use them. I haven’t used an epoxy solvent in 20 years.

There ya go, Epoxy 101. The final exam is on Thursday.