"Construction epoxy"?

[Harold Burrell]

In Chris Schwarz's book, "The Workbench Design Book", he mentions using Construction Epoxy in his building of the Roubo. Does anybody know what that is??? Or...what would you all recommend for a glue that would have a long open time?

[David Barnett]

In Chris Schwarz's book, "The Workbench Design Book", he mentions using Construction Epoxy in his building of the Roubo. Does anybody know what that is??? Or...what would you all recommend for a glue that would have a long open time?

Construction epoxies are usually more viscous and often rapid setting epoxies, such as Rezi-Weld from W.R. Meadows, which comes in a medium-viscosity paste form and also a thixotropic higher-viscosity gel. They are engineered to be especially good for gap filling. Some woodworkers may find construction epoxies to be more forgiving where joints are less than perfect, I suppose.

My own preference is for West Systems, though, where I can alter the properties to fit the job and choose the setting time with their various hardeners.

[Sean Hughto]

I don't know what Chris meant, but he typically answers emails, albeit with a delay if he is busy.

Perhaps somone with more knowledge would comment, but I always understood that slower setting epoxies gave better quality bonds. The little duel tube syringes of 5 minute stuff being convenient, but not the best, and instead, overnight more expensive stuff like PC7 being much better. Dunno, but I'll be interested to see the answers in this thread on "epoxy in woodworking - best practices and products."

[Harold Burrell]

I don't know what Chris meant, but he typically answers emails, albeit with a delay if he is busy.

Do you know his email?

[David Weaver]

IME, the only things I've had fail were with 5 minute epoxy, but they were in abusive situations, too, like items that would stay wet for a long period of time.

I'd imagine some of the construction epoxies are quick, and some of them are mostly filled material to keep the cost of the actual epoxy down, and maybe both.

To the extent that you want to make a filled epoxy, you can do that, too, as long as you aren't too cheap on the epoxy and too generous on the filler. 1 to 3 maybe? (epoxy to filler).

Any of the standard long-open epoxies are workable for quite a while, but you have to be careful as they are slick until they cure, and it's easy to clamp or not clamp something and come back later to find that it moved a *lot* before the epoxy cured, but then it did indeed cure after the joint moved out of position - and like jeffrey lebowski said... bummer man...it's a bummer.

[David Barnett]

Perhaps somone with more knowledge would comment, but I always understood that slower setting epoxies gave better quality bonds. The little duel tube syringes of 5 minute stuff being convenient, but not the best, and instead, overnight more expensive stuff like PC7 being much better.

This is almost always true although there are some newer, rather expensive short cure epoxies that are far better than there big box store predecessors. I've always considered the common 5-minute epoxies to be temporary or fixturing epoxies, and have used them because it was far easier to break the bond. For example, when faceting heat-sensitive gems, I'd often use epoxy to dop. After cutting and polishing, the gem would easily release after placing it in the freezer for awhile.

Although I have fixtured with epoxy in woodworking, I usually just hot glue things together then pop them loose with a mallet. I use 5-minute epoxy for fixturing difficult to chuck items on the lathe, too, and not just metal but everything from natural materials to glass and stone.

The overnight or 2-ton epoxies in the dual syringes will also work but the bond is generally far stronger than the 5-minute stuff.

[David Barnett]

To the extent that you want to make a filled epoxy, you can do that, too, as long as you aren't too cheap on the epoxy and too generous on the filler. 1 to 3 maybe? (epoxy to filler).

I keep a lot of 200 and 325 silica around for strengthening refractory moulds for casting pâte de verre and use that as a thickener with West Systems 105 resin. Cheap, strong, works great. Of course, you can buy colloidal silica from West, as well, or microballoons or fiber if preferred.

[David Weaver]

By the way, I haven't read anything re: the actual topic, but if Schwarz is writing about using construction epoxy, it's probably because it's miles cheaper than stuff like West System.

[Harold Burrell]

By the way, I haven't read anything re: the actual topic, but if Schwarz is writing about using construction epoxy, it's probably because it's miles cheaper than stuff like West System.

Yeah...me and Chris. We think alike.

[ian maybury]

I've some background around structural/engineering adhesives development - although not a lot with epoxies. The same sort of scenario tends to pop up in most cases though. There's a resin and and a cure chemistry (or -ies), and it's fundamentally this that determines the properties of the adhesives - both pre and post cure. There's then a list of potential modifiers and fillers to give maybe some flexibility, more conductivity, less weight, better wetting, less cost or whatever - but with relatively few exceptions these (based on watching chemists play with multiple formulations for specific applications) seem to deliver at the expensive of reducing the physical properties of the cured material. As most of the time do impurities....

Maximising properties tends to be about purity, and arranging conditions so that the substrate is properly prepared and the cure is as complete as is possible. Epoxies like some heat when curing for example.

An awful lot of so called adhesives development is voodoo - playing around with additives that don't do an awful lot, adding fillers to adjust the viscosity, adding dyes so you can talk it up/claim it's different from the pretty much identical product you sell for 1/10 of the cost in another application. The one that's become the norm in absence of a great deal happening in terms of the development of fundamentally new adhesive chemistries tends to be the placing of a well known adhesive in a new pack, and labelling it in terms of a chosen application rather than adhesive type.

Hence filled cyanoacrylates (superglues) masquerading as gap filling mitre bonders and the like - a possibility made feasible mostly by willingness to sell at a lower price/volume…..

[Malcolm Schweizer]

I think I qualify now as an "expert" on epoxy, as I have acidentally stuck more stuff to myself and other objects (including the cat) than anyone on this forum with it, and I am prepared to back that statement up! haha. Seriously- as a surfboard and boat builder by hobby and part-time trade, I use epoxies a lot and have played with many different brands and variations.

I interpret the "construction epoxy" statement as being ones that are made more for sticking stuff together, as opposed to wetting out cloth or coating things. These would typically be fast-setting, and might be more yellow or even brown in color. They also typically break down in UV exposure- which all epoxies do to some extent, but these are made to stick stuff together and not for exposed surfaces. I'm not the biggest fan of them. Epoxies like West 105, Silvertip, Raka, East Systems (yes- there is an east and west system!) are mostly clear, and are used for wetting cloth as well as sticking stuff together. They would typically (generally stated) be less viscous than a construction adhesive.

I am a big fan of West System, although I also use Raka, which is cheaper, but I have to order Raka and get West locally. I am with the other commenters- I like the ability to tailor the cure with different hardeners, or even with temperature control. I also heat the epoxy when I want a less viscous mix for filling tight-weave fabric or filling pores of wood. Every brand has its slight differences, and hence most folks tend to stick with one brand that they know all the qwerks of.

Please note- a warning about West System G5 epoxy, which a lot of people go with for sticking stuff together because it comes in small containers, and because of good advertising on West System's part- G5 is a flexible epoxy. It is not flexible like rubber, but it has a little bit of flexibility to it. Also it is very thick, and therefore does not penetrate as well as less viscous epoxies. What I have found with G5 is that:

(a) because it is thicker, it gives a slightly weaker joint when sticking part A to part B (less penetration)- not as big a deal when part A is a mortice and B is a tennon, but more when they are edge-glued, and

(b) It doesn't penetrate as deep as "regular" epoxy, so it might look clear, but when you varnish it will show up as a lighter area, and this includes if you had some squeeze-out and wiped it off, but it still got a little bit into the wood.
(c) because of the flexibilty, it's not as strong as "regular" epoxy. The same, by the way, goes for that smelly stuff that comes in two tubes that elmer's sells. It cures slightly flexible.

THAT is why I prefer wood glue for joinery unless said joinery is a boat or other object being subjected to water.

Well, okay- contrary to what I just said above, I do use epoxy to edge glue things like cutting boards, bench tops, and other things that are going to get planed/sanded well below the surface before varnish, so the whole squeeze-out causing splotchy finish is not an issue in those cases. Just note that also epoxy is slippery stuff, and it makes for a very difficult glue-up when edge-gluing (my opinion) as opposed to yellow wood glue or variations thereof.

Perhaps more than you asked, but just some thoughts on epoxy from my experiences.

[Sean Hughto]

Do you know his email?

chris@lostartpress.com

[george wilson]

I'm not a big epoxy user. But,for what it's worth,the maintenance Millwork Shop in Wmsbg. uses West System epoxy,with the microscopic glass bead powder for filler. They make a lot of outdoor furniture that is everywhere in the mile square museum,and needs repair a lot.They wish to avoid repair as much as possible,of course. They have the advice of the professional Architects employed there for choosing materials to use.

BTW,I was a bit gobsmacked to see what the carpenters were using to make benches for an out door theater: 16" square timbers of white oak,cut to seat height,one on each end,with long, heavy planks laid across. Wonder what that wood cost? And,there are a LOT of those benches as it is a pretty large theater setting.

[Pat Barry]

I recall David Marks using urea formaldehyde glue (plastic resin glue) on his Woodworks show numerous times when he needed a long open time for certain projects. I've never used it personally but I think he knows what he's talking about.

[george wilson]

Plastic resin glue was the old standard when I was in high school wood shop. Either that or hot hide glue.