Replies

1. 
   gerry001 | Jul 28, 2002 04:31am | #1

   The goal here is to achieve a very thin layer of glue over the mating surfaces. If this is done, it doesn't matter if you coat one or both edges. The problem with some glues and woods is the wetting action of the glue. In some cases, after applying the glue with a brush or roller, if you leave it sit for two minutes you may notice some areas with gaps in the glue coverage. When you join the edges together, there is no way of knowing if the squeeze out will cover this area. In this case, applying glue (thinly) to both edges just increases your confidence.

   From this, I've acquired the habit of using a brush as it seems to give better coverage, and to rebrush it just before assembly. Also, the old technique of sliding the edges together before clamping the boards serves the same purpose of ensuring full coverage.

   With long boards your fit will be less perfect than with shorter ones, and it's easier to miss a small area, so I tend to glue both edges. As to the fit aspect, I understand that yellow glue is not considered to be gap filling, but that term is relative, and a very small gap will still be filled with adequate strength.

   As in everything, there are no absolute rules. I can't think of anything that I would do the same in all cases. On that note, do you sand, machine joint, or hand plane your edges before gluing, in order to get the strongest joint? (See Hoadley, Understanding Wood). Finally, do you really care about the strongest joint? Perhaps that depends on how this will be used.

   Gerry

2. 
   RLMillard | Jul 28, 2002 02:27pm | #2

   I apply glue only to one edge of a joint. I aim for a thin but even coat. My main reason for this is that excess glue will be squeezed from the joint anyway, and it acts like grease, causing everything to slide around. I either work with full width or wide board, so I have only rarely needed more than two boards (and one joint) to make my project. Working this way, my glue is not exposed to the air for very long, but if I had many boards to glue together, I would probably still glue only one or two joints at a time. It is easier to break the job down, and it adds little or no time to the project to do so. The one exception to this is ( for me) is where I make my own lumber core plywood, in this case I slap a thick coat of glue to one edge and quickly clamp them together. I have made panels with as many as 12 narrow boards this way, but since they will be considerably reduced in thickness, the grease like action of the glue is not a big deal. In other words I can quickly take care of any misalignment when I surface the panel.

3. 
   denwdwrkr | Jul 29, 2002 05:24am | #3

   I have always just applied glue to just one side too.  And like you I have never had a joint failure.  Too much glue seems to be more of a problem.