Precision Puzzlemaking Primer -- Volume 1

Step 8 Gluing guidelines

Now that you've got all of these accurately cut wooden blocks, it's time to make some puzzles with them! Getting adjacent faces properly lined up is absolutely essential for these puzzles to function as intended. Doing this is a bit of an art form in and of itself, however here are a few pointers to help you along the way.

Work on the flattest and smoothest surface possible. I recommend using a granite surface plate (as shown) for maximum accuracy, however a small scrap of glass or mirror will probably work well in the short term. The only other alignment tool that you'll need is some sort of straight edge to press your pieces up against. I recommend using a thick parallel bar or a machinist's 1-2-3 block, but you can easily make do with a leftover section of square stick.

Use a quick setting yellow woodworking glue -- the brand doesn't matter as long as it contains aliphatic resin. I'm fond of Titebond #1, which I put in a plastic syringe to help to keep the glue under control as I'm applying it. I keep some masking tape wrapped around the syringe to seal off the end when I'm done with it, and I use a needle to clean out the tip when I take the tape off next time.

Put a few drops of glue onto one of the surfaces to be joined and then smear it around with your finger to ensure that it coats the wood evenly. Choose a finger to be the dedicated glue spreader -- pick one that you don't need to use to hold the pieces -- that way you don't have to worry about cleaning the glue off your finger right away. I use my right pinky finger.

After spreading the glue, but before pressing the blocks together, I recommend using a different finger to wipe excess glue away from the perimeter of the face that you just put it on. Look closely at the full size version of this image to see what I mean. This trick helps to minimize the amount of glue that squeezes out of the cracks between blocks.

If you get beads squeezing out of the cracks anyway, then there are two good ways to get it off:

• use a wet brush (or a wet finger) to immediately wipe away the excess glue. Aliphatic resin glue is water soluble, so it should clean off completely if you get at it right away.
• wait about 2 minutes and then carefully scrape the semi-hardened glue away with the edge of a razor blade. There is a reasonably short window of time during which this technique is effective, but if you hit that window then it works extremely well.

You only need to put glue on one of the surfaces to be joined -- leave the other one dry. When you do finally press the glued-coated block into place, use the flat granite plate and straight edge as alignment guides. Press the blocks together gently at first and rub them around a little help the wet glue soak into the other dry surface. As soon as you feel the glue start to get tacky (i.e. you're getting slight resistance to the rubbing motion) then press the blocks firmly down onto the granite surface plate, and back against the straight edge. Once you are confident that the force you're applying has got the blocks aligned properly, go ahead and squeeze them firmly together. Hold them this way for about 30 seconds and then let go and don't touch for about 3 minutes. Additional blocks may be carefully glued on after just a few more minutes of drying time, however you should wait at least half an hour before playing with the puzzle.

Put some thought into the order which you glue the blocks -- some ways will be better than others. A good rule of thumb in this regard is to not glue up complex puzzle pieces one block at a time... instead build them as two or three smaller subassemblies which you then join together to form the larger shapes.