I’ve been using epoxy in cabinetry for years. I like that it’s strong and has gap filling properties. I also liked (or wanted to beleive) that it was strong enough that would compensate for a less than idela joint. Lately though, I’ve had a couple of failures which have me re-considering. So, here goes:
Who uses Epoxy?
What brand?
What tecniques do you use to get good results?
I’d be especially interested to find an epoxy that can be used as glue without adding thickeners.
Replies
I am working on the millwork and furniture for a yacht. We use epoxy for several applications (sorry, can't remember the brands we use). We make a lot of curved panels out of several layers of bending plywood and use epoxy as it ensures that we get very little spring-back after the panel is taken off of the bending form. We also make a lot of curved moldings by laminating numerous layers of thick veneer. Again, epoxy ensures that we get strong joints and little or no springback. I have also used epoxy if I have a complex glue-up that requires a longer open time than a PVA will allow. If you have had failures with epoxy it might be due to the epoxy partially setting up before everything is clamped (avoid this by using a slower catalyst), or, perhaps the joint has been clamped too tightly and too much epoxy has been squeezed out of the joint.
It might be more helpful if you gave the details of the nature of your failures.
Some of us could write a book here and might not guess what went wrong on your project. I have probably used over 50 gallons over the last 20 years,
I usually buy the resin in 5 gallon pails, it is cheaper that way, and I usually buy a couple of different hardeners.
Since you are wanting an epoxy that doesn't need thickening, I have to ask If you have used it without?
Epoxy likes a fat joint. If you have done a perfect job of jointing two boards to be edge glued, then use epoxy, and clamp the hell out of it, because it is slow to set, and does not penetrate the cell walls, you may be squeezing it all out of the joint.
On the other hand if you have done a mortise and tenon joint that has a lot of space in it, you can mix enough filler to the thickness of mayo, or peanut butter, and get a great joint. Without the filler though, the epoxy may just run out, and what is left would be too brittle to bridge a big joint.
I've been using West epoxy. I brush unthickened epoxy until the wood appears to be saturated, then follow with a mix thickened with colloidal silica. My recent failures have included a joint in a maple butcher block and a plywood to poplar test joint. Because of it's width, it's possible that the butcher block had greater clamping pressure in some places than in others. The test joint was prepared in the same way and deliberately clamped with moderate pressure. In both cases, the joint failed. A similar joint made with Titebond fared far better. I've always liked epoxy because it had a predictable cure time and squeeze out sands relatively easily. I've recently added a good jointer and planer to my arsenal. Is it possible that my joints are TOO good?, or do I just need to pay extra attention to my clamping pressure? If my joints are really good, is epoxy overkill?
I am not sure that I am following what you are doing. If you are gluing a wide plank onto the face of PW, you are making a mistake that no glue will fix. If that is what you are trying to do, you should try something like silicone about 1/8" thick or 3M-5200. Anytime you are trying to glue something that moves like wood to something that either does not expand and contract at the same rate under the same conditions, you should try to use a flexible adhesive with enough elasticity to stretch that distance without loosing adhesion.If you are just edge-gluing, and they are well machined and fit tightly together, something like tightbond would be a better choice. Epoxy is long chines of molecules which are quite large, They do not penetrate the cell walls like most of the water-born glues, so for some woods, they do not get a good mechanical grip on what is there. On the other-hand, the glues that penetrate the cells actually fortify the cells and make them stronger than the wood around them.
Somewhat off of the point but I need advise regarding using epoxy as an inlay and can it be tinted/colored?
An article in the February 2002 (issue #73) Woodwork magazine by Michael Fortune (in my opinion he is the MAN) gave lots of detail and technique on this topic. His approach is very precise and labor intensive but his results are magnificent.
I think there was also an article on the topic somewhere in FWW magazine too (check the index).
Here's a link to back issues of Woodwork:
http://www.woodwork-mag.com/back_issues.html
Good luck with it!
Thanks for the reference. This is exactly the type of information I was hoping for. I will order the article. Don't ya just love the internet!
Doug
Jeff Miller has the article in FWW in the May/June 1996 issue. System 3 has added a line of colorants for their epoxies and I'm going to try their products for this project. Again, thanks to all.
Edited 3/8/2006 12:18 pm by DougF
Yes, that was the article I was thinking of in FWW. Jeff Miller is another author whom I think is really excellent - practical, reliable, tested and true stuff.
Good luck on the project!
I agree . I have several of his books and they are excellent.
Thanks again.
Yep, use the colorants made for epoxy. I did a black table strictly with colored epoxy, when the dye job went south. The epoxy will have a bit of a translucense to it, meaning, it won't be a solid opaque color, unless you add a lot of color to it. i know the colorant is available in red, black and brown, probably have more colors just haven't used them yet.Furniture...the Art of a FurnitureMaker
Earl, thanks for the info. I contacted a fiberglass specialists and they have the colorant. Everyone's been a great help.
Doug
Surfboard shops use a colorant that cmaes in small bottles that will do what you want. You will need to learn to mix colors properly but its a great use for what you s=describe. I also use brown and red to make pitch pockets out of voids in cherry wood before I finish. aloha, mike
Mike, thanks for the information. I tried a test fill using a color paste made for use to color epoxy made by System 3 and it worked great. I also found another source from a shop that repairs fiberglass boats. It is truly amazing what is out there when you ask. For what it is worth, another post referred mw to a 2002 issue of Woodwork. I order it and reviewed it last night and it has a wonderful article on accent inlays using some very interesting materials, including epoxy. The one that caught my interest was using strips of black PVC to simulate ebony inlays. I highly recommend the article. It was issue number 73.
Doug
Edited 3/14/2006 9:34 am by DougF
Epoxy does have gap filling abilities, but the heat that it generates when curing can cause the epoxy to become over viscous and starve the joint by flowing out or to the bottom. Try adding wood flour or cotton strands to the epoxy (after mixing in the hardener) this will dramatically increase the epoxy's gap filling ability.
I've used epoxy for years, especially for sloppy joints. It generally holds quite well and puts a mechanical lock into lots of joints.
I'm a little reluctant to use epoxy in larger cross grain joints; I've seen it work loose due to the differential movement between the long and cross grain in a long mortise and tenon. The epoxy is stiff and hard and cannot accomodate a little movement the same way that a PVA type glue can flex.
For boats, there's no other glue I'd use.
A thick epoxy that needs no filler, System Three T88
Bobby
I would contact the tech folks with the epoxy you use. All the companies I deal with have manuals and tech folks to discuss applications. The manuals are free and ususally downloadable. If your joint failed it sounds like you might have treated the joint like a PVA glue and squeezed all the glue out. You certainly don't use the same clamp pressure with epoxy. I go through dozens of gallons a year in our shop. We use System3 but I don't see much difference in the major companies as far as quality. Does your epoxy company have a manual or are you using the stuff from a hardware store??? Different companies have different mixing ratios. We had a youg guy forget to read the directions on the bottle and he mixed the wrong ratio so that was a problem but he only did that once. Once is all you are allowed to make a mistake here.
I've used West epoxy and use their pumps to measure it.
I think RickL's point about mixing ratios may be a critical one. Accuracy in measuring out resin and hardener matters, as the resulting epoxy is strongest when mixed at the proper ratio. It can be very weak if mixed less thoroughly or at the wrong ratio.
Epoxy is certainly not my main go-to glue, but I really don't understand why it isn't used in more woodworking applications.
For, say, edge gluing, it's obviously a poor choice. It likes a thick glue line and rough surfaces to grab.
But for Krenov style doweling, I use epoxy for the part of the dowel going into side grain. (I do the glue up in two seperate stages.) I think a PVA is weak in that part of the joint, unlike the other half of the joint where the dowel going into long grain will bind just fine with PVA. Have had very good results with this approach.
I like System Three T88 for the most strength and a slow set. And I like S.T. quick set when I don't want to wait, like for general shop stuff such as jigs, and certain hardware.
I think it would be hard to repair an epoxied joint that was failing.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
Epoxy binds well to itself and fills gaps with strength so you ought to be able to repair failing epoxy joints. So far I haven't had to, knock on wood.
I have used a lot of brands of epoxy and I have some favs for certain apps. Gougeon Bros West System is the most all around product and Systems 3 is very similar. T88 Structural is good for solid bonding of structural and disimilar materials like steel to wood. I dont use it very often. The 5 minute varieties have their place but are not that useful for most woodworking projects. Because I live in a warm climate, I use slow or extra slow hardener and quite often add thicksil to thicken the mix. This has been the most satisfactory formula for me for laminating with clamps or vacuum. I never use microballoons as they weaken the material although some like it for its easy sanding as a fairing material. I've had failures with epoxy and few of them were the materials fault-wrong mix, contamination, oily wood not prepared properly, etc. Gap filling is best accomplished with microfibers or thicksil as it really strengthens the fill material. aloha, mike
Because epoxy absorbs into the wood it can leave the joint starved and thus fail. Boat builders use a 2 part epoxy made by West System. They have an additive made from finely chopped cotton, almost a powder, that turns the epoxy white but holds on to the epoxy and makes the joint indestructable. They also have a filler called "micro baloons" for larger gaps, but this does not replace the cotton. I haved used this on my wood boat as well as some wood projects I have made in the past. I find epoxy diffcult to work with and use it only when the application calls for it. It is also expensive. You can buy it a your local marine supply or on-line.
With all of the talk about glue and epoxy, I've made an un-fruitful search for some scientific data as to adhesive strengths. Something that compares strengths both medially and laterally, as well as flexibility.
For instance, when to use Titebond III vs System Three epoxy. There has to be some un-biased lab data out there somewhere that compares adhesive characteristics. Does anyone know of any such data?
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