Replies

1. 
   Sean2112 | Dec 28, 2007 05:00am | #1

   If you glue two pieces of wood with incompatible annular rings, they will not be even over time unless you are able to maintain the environment in which you glued them together.  You need to be very aware of the radial and tangential sections of your pieces when you plan your glue-up. Also woods with different moisture contents will climatize apart from each other.

   Sorry I don't have any easy answers, but if it was easy, anyone could do it.

   Regards, Sean

2. 
   PCM | Dec 28, 2007 05:07am | #2

   If you are using yellow carpenters glue (pva), that may be the problem. That type of glue has a tendency to "creep". Sand it down, finish, it may reappear. If you have a solid-no gap glue line, I would try polyurethane glue next time.

   Pete  

3. 
   MikeHennessy | Dec 28, 2007 03:24pm | #3

   Moisture. What I have always heard is that the moisture in the glue causes the surrounding wood to swell. I also wonder if it could also be caused by the wood away from the joint drying out and shrinking, while the wood fibers at the glue line do not, since they are sealed by the glue (which doesn't shrink either), resulting in a raised glue line.

   This relates to another thread (or three or four) about clamping pressure. It seems to me that increasing clamping pressure would minimize this phenomenon. Higher pressure = less glue = less effect on subsequent wood movement. Dunno. Just thinkin' out loud.

   Mike Hennessy
   Pittsburgh, PA

4. 
   hammer1 | Dec 28, 2007 07:15pm | #4

   Once the glue dries, it's a solid entity. The wood shrinks, particularly this time of year, the glue doesn't. It's not noticeable in every case, sometimes it's just for a little way on one or more joints. I think part of it is the glue and part is the wood species. White and yellow glues seem more prone as do species like red oak. I can't help but wonder if a common glue like Titebond has had chemical changes over the years. I've used it a long time, 40 yrs. and never had the problem until recently.

   I happened to take some pictures of a panel I glued up. The pieces fit perfectly, I was careful with glue application, not much squeeze out. Once finished and put to use, the very last joint had the problem, Go figure, in this multi board panel. Did that area not fit as tight as it looked? Was there too much glue, not enough pressure? I don't really know but I've switched to liquid hide glue.

   Beat it to fit / Paint it to match

   
1. 
   colebearanimals | Dec 28, 2007 07:27pm | #5

   Hi hammer,

             Like your pipe insulation trick.

                                                            Paul

2. 
   stpatrick | Jan 15, 2008 03:03am | #7

   ditto the comment on the pipe insulation: great idea

5. 
   Woodrat1 | Jan 14, 2008 04:34pm | #6

   Hi,

   One of the most recent issues of Fine Woodworking has
   an article on glue joints. Frankly - I thought that the article
   was a bit ridiculous - but in defense of the author - it is tough
   to write a comprehensive article on wood / glue technology
   in a finite amount of space.

   My take away from the article was "the more clamping pressure,
   the better". That may dovetail into Mike Hennessey's response of:

   "This relates to another thread (or three or four) about clamping pressure. It seems to me that increasing clamping pressure would minimize this phenomenon. Higher pressure = less glue = less effect on subsequent wood movement."

   Bill-