Replies

1. 
   Alan | Apr 14, 2002 01:32pm | #1

   1Sylvain,

   I have quite a bit of experience using epoxy with wood.  It is a very strong adhesive for wood (not a difficult trick--wood is easily bonded) and when used properly it has excellent gap filling ability--the epoxy in the gaps can be stronger than the wood it replaces.  It is not, however, a cure-all--despite what the Gougeon brothers might think.

   If the joints are REALLY loose, you might want to think about using something to shim out the pieces to make the joint tight (veneer, perhaps, depending...) rather than relying on the adhesive to fill up the empty spaces.

   If you decide to use epoxy, remember that you will have to somehow hold the pieces in proper alignment while the epoxy cures.  Be sure to keep the epoxy off any finish surfaces:  one of its attributes is that it soaks into the wood quite well--that's one reason it makes such a strong bond--but that also means you cannot get rid of all of it if it strays onto places it doesn't belong;  it will effectively seal the wood from any stain or dye you might want to apply after the glue-up.  Be absolutely sure to wear gloves (nitrile are best with epoxy, I believe) goggles, a respirator--if you're working in a fairly closed space--long sleeves and an apron, or other coverall that you are willing to sacrifice.  Nothing, but NOTHING can get epoxy out of a garment.

   (As an aside, it will also seal the wood from moisture.  It is absolutely, one hundred percent waterproof!  If you are worried about moisture content variations ruining your work, incapsulating the wood entirely with epoxy prevents the transfer of moisture into or out of the wood.  This is another reason it works so well in boat construction--or construction of anything that would otherwise be subject to great variations in moisture content.)

   All kidding aside, the Gougeon brothers' book, The Gougeon Brothers On Boat Construction:  Wood and West System Materials, is a great reference and "how-to" for using epoxy in woodworking.  You might want to look at it in the library to learn about the stuff's pros and cons, the different qualities of hardeners and resins, and the use of various fillers.

   Not much of an answer, was it.  But you asked a question which, like many questions on this site, IMHO, doesn't really have a simple answer.

   Alan

1. 
   scx297 | Apr 15, 2002 01:36am | #2

   Alan,

   thanks very much for your reply. You are saying to keep the epoxy off any surfaces  to be finished. If any glue get on a surface to be finished and I remove it , let say in the next 5 minutes with lacquer-thinner, will that affect the surface anyway?

1. 
   Alan | Apr 15, 2002 08:41pm | #3

   1Sylvain,

   Maybe.  (Yet more equivocation.)  If you get it on bare wood it will almost certainly seal it.  The only circumstance which I can think of where it wouldn't seal the surface of bare wood is if the epoxy is partially cured before it hits the bare wood.  As you know, newly mixed epoxy, if it has no fillers, is thin enough to move about pretty easily, and it soaks into wood quite readily--especially on end grain or on open-pored wood such as oak, walnut, mahogany, etc.  If there is already a sealer on the wood, the epoxy is less likely to penetrate (but then you wouldn't be too worried about it).

   I feel like my first post was way too much.  In retrospect I think your project is probably not extensive enough to worry about everything I wrote about.  Sorry.  But I have talent for getting long-winded.

   Alan

2. 
   Elcoholic | Apr 15, 2002 10:32pm | #4

   If the chairs are of any value as antiques, using epoxy will reduce their collector value while quite paradoxially greatly increasing their values as chairs.  Of course refinishing will do the same.

   I believe the right solvent for wet epoxy is acetone.

   West Systems is as good as it gets (IMHO).  Besides their fillers, it can be thickened with sawdust and colored with polyester pigments.  Just remember to mix the resin and hardener for the recommended time before you add any thing else or it won't go off.  Not withstanding the nooks and cranies around chair joints, I have no problem sanding filled cracks, bark inclusions, knot holes flush in bare wood without any finishing problems. 

   John O'Connell - JKO Handcrafted Woodworking

   Life is tough.  It's tougher if you're stupid - John Wayne

3. 
   PaulCraft | Apr 16, 2002 01:12am | #5

   Well... It depends. There's a best glue for a number of different circumstances.

   If these are valuable old chairs you may want to use hide or slow cure white glue. You can fit the tenons with veneer shims to tighten up the joints.

   If these are old chairs of no particular value (or if you don't care about their value as antiques) and you happen to like them and want to use them a while, then, properly used, epoxy will work well.

   As Alan said The Gougeon Brothers book is an excellent source of good information. An alternative to the West system is System 3 Epoxies. They also have some good information. Both are very nice product lines.

   However, be warned. Chairs are stress based systems and they wear out. When the wood dries out, the adhesives fatigue and the joints are eroded by motion, you really cannot restore them back to their original strength. Really valuable antique chairs should not be used for sitting. I have been fairly successful keeping some old English barley twist cafe chairs in working order for about 20 years. It has been a constant battle. Now I'm seeing twists appear in rails and legs which pull the chairs apart. These chairs were "cheap" chairs when they were made. The joinery probably was never real tight and they have flaws such as diagonal grain across spindles which are beginning to prove fatal.

   Good luck!!!

4. 
   jeffn7 | Apr 17, 2002 12:38am | #6

   I don't think the type of glue you use is going to be the issue, assuming you are using a good quality glue. The reason I say that is that Titebond II (the yellow glue I prefer) and epoxy are adhesives that cure to be stronger than the wood fibers they are joining. In short, the wood fails before the glue does.

   It sounds like you should consider improving the fit of the joinery, as several posts have already noted.

   As for the glue itself, I'm a fan of titebond II for almost all projects. It's easy to clean up (as long as you get it before it sets up!) and forms a very reliable bond. I do use epoxy for some outdoor stuff, but I'll use titebond for that as well providing it's not subject to hard conditions. The thing that I don't like about epoxy is the mess it makes when it foams up during the cure process, I know it's easy to scape off but it always needs more attention after scraping. Also, if you get the stuff on your skin you will be wearing it for at least a week, it just doesn't come off.

1. 
   SgianDubh | Apr 17, 2002 03:53am | #7

   jeff, Your description in the last paragraph sound suspiciously like the characteristics of polyurethane glue, rather than epoxy. A wee slip in the mindset, maybe? It happens to us all. <g>  Slainte.

1. 
   jeffn7 | Apr 17, 2002 05:59am | #9

   yeah, a slip... maybe too much glue fumes in the shop today.

   but I will try to maintain my honor and dignity by suggesting that the joinery is *generally* more important than the glue, and that epoxy will do a better job than poly or yellow at securing a loose joint.

1. 
   Upraiser | Apr 17, 2002 08:16am | #10

   The new hot melt poly glue is in a class by itself.  I would not be afraid to use it to repair some furniture and plan to do just that.

   I agree, it should not be used on some valuable antique, but our every day dining chairs are begining to get some loose joints and I will use it on them.

   I have used it and tested it.  It is an excellent product. It is nothing like the "old fashioned" hot glue.

   It goes on very thin, sets in 30 sec. to 90 sec., glues up anything.

   Costly stuff, but it will change the way you build and glue things up.

   Curt

1. 
   Elcoholic | Apr 17, 2002 10:24pm | #11

   Which brand are you using and what others did you try.John O'Connell - JKO Handcrafted Woodworking

   Life is tough.  It's tougher if you're stupid - John Wayne

2. 
   Upraiser | Apr 18, 2002 12:08am | #12

   John

   I have used the new Titebond product that was introduced about the first of the year as a kit, gun and three types of glue.  Multipurpose, and two types of wood glue 30 sec. set and a 90 sec set.

   I have been very impressed with all of it, however the 30 sec stuff seems to take longer than the 90 sec. set.   Full strength in 24 hours, but at least 90% in a less than an hour or so.

   Very strong end grain to end grain, plywood end to end, end to side etc.  none of which could be broken by hand. They were about 2" x 4" blocks.   I knocked them apart with a 3# dead blow hammer and it took wood with it.

   I even glued up a 35 year old tire on my wheel barrow. It had a big split , tube sticking out,  I had taken it off to replace it.  Decided I had nothing to loose, so I glued in a boot, then glued the break which was ragged and about 2" long.  Left it 24 hours, put it back and put in 25# of air.  Filled it with so many concrete blocks that I could not pick it up, no problem.

   The glue comes out a lot thinner than the old hot melt stuff.  Flows out nice and thin, does not expand.  It is easy to slice off the excess.  Dries a opake clear.  Makes nice tight joints.

   The gun can be separated from the power unit for 20 minutes, it takes about 30 minutes for it to heat the tube.

   It is impressive to say the least.  I want to test it on an out door application to see how it stands up to the weather and water.

   Curt

2. 
   LD | Apr 17, 2002 05:44am | #8

   Your description sounds more like polyurethane glues than epoxies.