Epoxy

[Mark W Pugh]

OK, I always have a small amount of epoxy around the shop. I want to expand my use of it, so not just for woodworking. There are a plethora of selections out there. I'm looking for a system that has a medium cure time. Also, the ease of making small batches vs large batches would be helpful. Not only do I use it for glue ups, but knot filling and other projects.

What do you guys use and recommend?

I assume there is not a shelf life issue with the resin and hardeners.

Thanks

[Larry Edgerton]

I rely on West System. Their experience is vast and their tech line is second to none.

Larry

[Dave Richards]

I've used epoxy from Raka.com for about 15 years. Always had excellent results and gotten top notch customer service.

[James Tibbetts]

Check out West System. They will cover about any need you have. For small batch mixing I got a sleeve of medicine cups from my local pharmacy; 50 for about a $2. They are graduated in oz, dram,and mls.

[Mark W Pugh]

. For small batch mixing I got a sleeve of medicine cups from my local pharmacy; 50 for about a $2. They are graduated in oz, dram,and mls.

Now that is a great idea!!

[Ken Krawford]

For small batch mixing I got a sleeve of medicine cups from my local pharmacy; 50 for about a $2. They are graduated in oz, dram,and mls.

Lee Valley also sells them. http://www.leevalley.com/us/Garden/page.aspx?p=20009&cat=2,33134&ap=1
I use the Bondo epoxy sold at Home Depot. Ten drops of hardener per oz of resin and the 1 oz cups makes it easy to calculate small batches. It cures in about 2 hrs.

[David Hawxhurst]

i use the thin and thick epoxy from US Composites. for small batches i use a scale and do it by weight, us composites says its more accurate then doing it by volume for small batches.

[Art Mann]

I use System Three epoxies but I am familiar with West and Raka as well. They are all used in boat building and they are all good materials. The cure time is dependent upon the hardener formulation. You can get it formulated with very long and very short cure times and you can blend hardeners to get the cure time you need. I got started using System Three because they provide a very useful free book on using their product in various applications. If you buy in gallon quantities, you can get a pump that screws into the bottles and allows very accurate measurement and mixing of small batches. I'm not sure about smaller bottles but it is worth looking into.

[Wade Lippman]

My West System stuff is about 10 years old now. It still works fine, but the hardener has gone a dark mahogany color. It you don't mind that, it has an infinite shelf life.

[Bill McNiel]

West System's pump approach is great for both small and large batches. I use their products for glueing, gap filling, fairing and surface finish for counters and tables (Base coat(s) of 207 with Waterlox as the top coat(s)).

[John Schweikert]

There are a dozen or more name brand epoxy lines which will all do nearly an equal job. Take your pick from cost to specific needs. Epoxy with a 2:1 ratio is by far the easiest to measure but 3:1, 4:1 and 5:1 also exist. West System is a well known product from the Gougeon brothers, but many more brands can match the quality now. It's not a trade secret anymore how epoxy is made.

MAS, West, East, System Three, MarinEpoxy, US Composites, Raka, Total Boat to name a few.

My personal experience is with MarinEpoxy and System Three and both are excellent. I prefer a medium hardener. I can keep my insulated shed at a consistent 65-70* all year around with a small AC unit and space heater. Medium hardener has given the best balance of pot life and working time and ready time to sanding for my boat build. Some companies only have slow or fast which I am not interested in currently. Some epoxies are truly blush free and some claim to be but aren't and still require a wash before sanding or recoating after 24 hrs. Some epoxies will be yellow and some truly clear. Viscosity varies in epoxies due to intended use of gluing, gap filling or wetting out fiberglass and more.

If you only need small amounts then I'd say you are fine going with the big names, but when it comes to volume, money can be saved yet still get high quality epoxy from places such as RAKA, MarinEpoxy (from Bateau) and US Composites for example.

Pumps are a good way to measure resin and hardener, but if you don't regularly use the pumps you truly risk errors in the ratio. A simple digital kitchen scale (I bought one for under $20 from Amazon) will always give the exact ratio no matter what. Weight ratios are NOT the same as volume ratios though, so follow the info on the product labeling. Incorrect ratios (and mixing) are the main cause for epoxy failures. While there is a little wiggle room, that also varies between brands. For the epoxy I use, the 2:1 volume ratio is a 100:43 weight ratio. If I am measuring volume more than a few pumps then I use the System Three 14 oz graduated cups, accurate, flat bottomed and sturdy enough for a few uses if wiped clean. The 1 qt paint mixing plastic cups are excellent for larger batches, but get that epoxy out onto the surface promptly after mixing. The larger the volume of mixed epoxy the faster it sets (very short pot life)

Mixing epoxy is also just as important as anything else. I use either reusable plastic cups or one off wide bottom paper ice cream cups. I cut flat the rounded end from tongue depressors with wire cutters. A flat stick can get to all the areas in the cup bottom for a good mixing. Some people transfer the mix to another cup for a final mix. I see no issue in that process but I use only one cup, mix well and never have issues.

[John Downey]

Sounds like you've gotten plenty of good advice here.

I've used a lot of West System in a shop where we did about 60% mesquite work. Lots of voids and stuff to fill. We dyed it black with Proline universal tint. A real paint store should have it or something similar. Sometimes you see it in hardware stores but it's pretty hit or miss. Only a drop or two is needed usually. Too much makes the epoxy a bit gummy - but that is much more noticeable in 5 minute epoxies. There are all sorts of ways of turning epoxy black, but if you're doing large amounts, an off the shelf tinting agent is the way to go.

One thing to watch with epoxy filling is heat. Epoxy curing generates heat and a big void can smoke and bubble and crack as it cools. If you're pouring more than a few ounces you may want to reduce the catalyst some. The manufacturer may have a specific catalyst for this too, could be we just always had the wrong one :D

5 minute epoxies don't seem to have this problem, or maybe they are always used in such small quantities that it just doesn't come up.

[Alan Schwabacher]

The recommendation to watch out for large amounts of epoxy is good. Epoxy makes heat as it cures, and small batches or thin layers can get rid of that heat without problem. Large containers mixed exactly as had worked on a small scale can heat up enough to char.

But the solution is to mix smaller batches, use a much slower hardener, and/or to keep large batches in shallow trays, not to add less "catalyst". Adding less catalyst works well for the kinds of plastics cured by a catalyst, but epoxies are cured by mixing a resin and a hardener that must be mixed in the correct ratio to end up with good properties of the final material.

Adding less of one component is like leaving out some of the tenons in your mortise and tenon joints: you would compromise the structure.

[John Coloccia]

I prefer West, but System 3 is good as well. I would suggest just finding what you can source locally. I have a local source for West...typically found in marine and hobby shops. Woodcraft tends to carry System 3.

re: West hardeners turning dark
Send them an e-mail to double check, but I believe you can gently heat it in the microwave and turn it clean again if you really want to. As far as I know, the shelf life is indefinite, even after it's turned colors. I've never heard of West getting too old.

[John Downey]

But the solution is to mix smaller batches, use a much slower hardener, and/or to keep large batches in shallow trays, not to add less "catalyst". Adding less catalyst works well for the kinds of plastics cured by a catalyst, but epoxies are cured by mixing a resin and a hardener that must be mixed in the correct ratio to end up with good properties of the final material.

Fair enough, that sounds like good advice to me :D

[Kevin Jenness]

Be advised that epoxy, unlike some other adhesives, requires a sawn or sanded surface on any but the least dense woods for good adhesion. Gougeon Bros.(west system) recommends sanding with 80#.

[John Coloccia]

Be advised that epoxy, unlike some other adhesives, requires a sawn or sanded surface on any but the least dense woods for good adhesion. Gougeon Bros.(west system) recommends sanding with 80#.

They can also be clamped too dry with ordinary, home workshop clamping pressure. PVAs can theoretically be clamped dry, but typically only under industrial press loads. Epoxy's not the best choice for invisible joints.

[Bob Michaels]

I have used West extensively for work ranging from structural repairs on historic buildings to building period outswing garage doors with arched windows. I formed the arch trim by installing short segments and fairing the arch with thickened West epoxy. Next day I just sanded to the arch I preferred. The large mortise and tenons for the garage doors were secured with wetted out West and thickened West to take up any gaps. Finally, I draw bored and pegged the M & T joints after coating the pegs with West. When using thickened West, I mix in clean cottage cheese tubs and spread the thickened mixture out about 1/16" to1/8" thick on a 8" x 12" piece of 1/4" mdf so it doesn't harden too fast in hot weather. West produces an excellent guide. Just google their website. in other exterior work, I have rebuilt wood sills of rotted plate glass windows in retail storefronts and these were done in-place without disturbing the 6' x 8' plate glass windows. I just cut out the rotted areas and replaced whatever odd shape came out with new wood coated with West and set in the void where the rot was. Finally, I coated the entire wood window sill with 2 coats clear West and then painted the sill to protect from UV rays. west also makes small squeeze bottles of a little thicker epoxy that you simply lay out a strip of epoxy and another strip of hardener and mix. Great for very small jobs. Check out their website.

[Brian Jarnell]

I like the West System, in particular there range of fillers.