Closing the Box

"Closing the box," or finally attaching the top and back to the rib structure, is a sort of milestone for building a violin. Some luthiers even go out and celebrate every time they close a box.

This process first consists of "turning the edges," or creating a smooth, even rounding along the entire edge of both plates. The corners are saved for after the neck is set into the instrument, simply because of their fragility. Turning the edges will not only provide an aesthetically pleasing look, and one that will wear less. It also helps the finish adhere to the edges of the plates.

Next, locating pins are made to fit the holes we drilled when we spot-glued the plates. The picture on the right is kind of fuzzy, but the pin is notched so that the cross-section becomes a semi-circle, allowing it to fit snugly against the purfling. These pins will make sure we get the plates in exactly the same place they were when we spot-glued. They will also keep the plates from slipping while gluing them up.

Speaking of glue, before I even want to think about gluing the plate on, I heat up my hide glue and coat the ends of the blocks with it. Right now I'm only worried about gluing the back on, so I'll get to the top quite a bit later. The glue must be applied to the blocks several times, because it likes to soak in to the exposed end-grain. Then I come around and apply glue to the ribs and linings.

Once the glue is thoroughly dried, I can "dry-clamp" the back on. I stick in the locating pins, put the back on where it belongs, and go around the whole body of the instrument with my spool clamps (pictured on right). Then I peruse the entire edge, looking for gaps. In this case, there were none. But if there were, I'd be going in with a plane or scrapers to remove any high or low spots that might be causing them.

Hide glue only has a working time of about thirty seconds to a minute, depending on temperature and humidity. This means that as soon as you remove it from the warmth of its water bath, you have thirty seconds to apply it to the gluing surface and get it clamped up. That's not enough time to clamp an entire instrument, so the gluing is done in stages. Incidentally, hot hide glue is also a very poor gap-filler, so it encourages (and demands) perfection from the craftsman. So why bother with hide glue? A lot of wood glues boast that the joint is stronger than the wood. That's a great thing most of the time. But for a musical instrument, what it means is that if you bang it on the side of a music stand or if the expansion and contraction of the wood on an aged instrument simply puts too much stress into it, the wood will break instead of the glue. That makes repairs less fun. Titebond is often used on guitars because you can always reach inside through the soundhole. But on a violin, eventually, the top will have to come off for a repair. So they're made to be removable. They have the overhanging margins and they're held together with the more brittle hide glue. It's still a lot of work to remove a top, and should only be done by a professional (unless you want to explain to the professional later exactly how it was that you contributed to the problem). But the hide glue makes things much easier.
Well, that was a long lecture with no pictures, so here's the trick I use. I open three or four spool clamps at a time, use a pallette knife to apply 145 degree fahrenheit water (ideal hide glue temperature) in the joint, and close the clamps back up. This reactivates the hide glue, gives me a slightly weakened bond for when the top does have to come off, and minimizes the amount of cleanup I would have had to do if I'd actually gone in there with hot hide glue on my pallette knife.


I wait overnight for the glue to cure to full strength, then I remove the clamps and I'm ready to extract the mold. I just go in there with a sharpened pallette knife to break the bond between the blocks and the mold. Hide glue bonds should snap, not creak, when they're breaking. So if there's an uncomfortable creaking sound, it's probably the block splitting. That's what you want to avoid.


Just push (gently please) on the block to see whether you successfully broke the bond. If you try to extract the mold and a block is still attached, terrible things could happen...





To demonstrate, here's a picture of the actual mold extraction. Get a firm grip on the mold and lift it up at one of the end blocks. Gently tap on that block with a small hammer. Switch from the end block to the neck block repeatedly to shimmy the mold out of there. It is thick enough that if you attempt to remove it from one end only, you will probably crack the ribs.
So there's the rib structure and the back, with no mold. It always feels surprisingly light at this point. The next thing to do is install the linings for the top and bevel them the way we did for the back. Here's a photo of the bevelling process. I just use a knife to do this, taking care not to dig into the ribs at all. The linings are bevelled so that there won't be a sudden change in the stiffness of the ribs where they begin, which would be prime real estate for a crack.

Now I get to shape the blocks. To do this, I use a chisel for the end blocks and an incannel gouge for the corner blocks. The main purpose of this process is to remove weight from inside the instrument. How much weight? I was curious, so I measured before and after. The fiddle lost 12 grams. It doesn't sound like a lot, but for a fiddle, that's not too shabby. That's like going down two dress sizes. Or something like that.


The pictures look scary, but I'm using a very controlled chopping motion with my chisel and gouge. The idea is basically to split the wood and clean it up afterwards. So make sure when buying blockwood to get the straightest-grained stuff you can find.


Now that looks much better.
Now I punch in my serial number on the neck block, where it will be visible to anyone looking in through the hole for the endbutton. I'll save time in the blogging process and explain that the top goes on pretty much exactly with the back, starting with coating the ends of those freshly-shaped blocks with hide glue...
And voila! My box is closed.
Mmmm... So tasty...
Next, I'll be blogging about the beginning process for two separate fiddle necks. But for now, I'm going to take a break, and give a break to my readers after that oh-so-long-winded blog. Now you see why I can't do Twitter.