Keyboard: Applying finish

A view of the keys with one coat of Danish oil applied:


Even with just one coat, the keys have taken on a subtle sheen and the naturals have become more golden-coloured.

At least one more coat to go...

Keyboard: Keys rounded over

A good keyboard has all sharp wooden edges and corners eased to avoid discomfort. In addition, the front portions of the naturals have their edges and corners noticeably rounded over: this is partly cosmetic, but I think it also protects the fingers when the hands skim along the keys during performance.

I eased both naturals and accidentals with 600-grit sandpaper; a few swipes were usually enough to do the job. To round over the front parts of the naturals, I used 320-grit paper and sanded up to the first scribe line, holding a razor blade on edge in the line to keep from sanding too far back:


This rounding-over provides some nice shadow lines, in addition to being comfortable under the fingers.

The only thing left to do now is apply finish to the keys. I plan to use two coats of a clear Danish oil (an oil/varnish blend), followed by a light application of paste wax. Perhaps at some point in the future this might need to be re-done when the keys wear, but reapplying an oil finish is not at all difficult. Polyurethane is to be avoided on keyboards, as I've heard it wears off irregularly and looks awful after a while.

Keyboard: Details

Some further work on the keyboard:

Behind each sharp, I stained the top surface of the key lever black with an ebony stain for about a half-inch. This is a purely cosmetic detail often found on instruments with dark-coloured accidentals, and makes the sharp seem to blend into the back of the key. I did not stain any part of the key that is hidden behind the nameboard.

Each rack slot was rubbed with a very soft 6B graphite pencil to lubricate the slot and reduce any rubbing noises when the keys are played. The one minor defect in the rack guide design is that the slots run perpendicular to the grain: hence the rack pins bear on severed end grain fibers, which are a little rough. Fortunately the noise is usually covered by the music.

The stand, stained and finished

To take advantage of a recent stretch of good weather, I took the stand outdoors and, with my mother's help, applied stain and finish:


The legs and stretchers were first treated with a wood conditioner to minimize blotching, which maple can be prone to. Then two coats of a dark walnut gel stain were applied. When the stain was dry, four coats of satin finish (some kind of lacquer in aerosol form) were sprayed on and the final coat lightly rubbed with 0000 steel wool.

Now the interior moldings and the legs are a pretty decent colour match. I plan to make the music desk out of maple and finish it the exact same way.

Keyboard: Levelling keys

After correcting unwanted tilt and unsightly gaps, the final cosmetic adjustment to the key positions is to ensure the rows of naturals and sharps are each at a consistent horizontal level. This is accomplished with paper shims of various thicknesses, which are placed under the red balance pin felt that insulates each key from the key frame.

I did this levelling strictly by eye. Usually a proper levelling is assisted with a thread stretched along the key fronts as a guide, but for now here's the result using my good old-fashioned eyeballs:


Levelling must take place after balancing, because the keys might not fall back properly until balanced and this could affect the level of the front edges.

The quantity of shims together with the thickness of the red head stop cloth under the key fronts gives a depth of touch of 1/4", which is typical for an Italian harpsichord. Maximum depth is determined by the sharps: if they are level with the naturals when depressed, the touch is too deep and extra notes might get played by mistake. On an instrument with two rows of jacks, the minimum depth must be enough for both rows to play successfully, as they pluck one after the other and not simultaneously.

I may have to repeat the levelling process in future, when the instrument is finally playing and the various action felts start getting compressed.

Keyboard: Balancing keys

Each key on the keyboard needs to be balanced so that it falls back reliably when played and released. This is accomplished either by lightening the portion of the key in front of the balance rail, or by weighting the portion behind the balance rail, or sometimes a combination of both.

French harpsichords usually employ the first approach, undercutting the undersides of the playing portions of the keys quite a bit to eliminate as much forward weight as practical. This approach can be used on other instruments as well. Since my keyboard is made of basswood, instead of a hardwood like beech or chestnut more typical of the Italian harpsichord-making tradition, I elected to balance my keys by weighting, which I think may also give them the slightly heavier feel of hardwood key levers.

By balancing my keys individually on a thin slip of wood, I found all of them to be front-heavy: not surprising, given that these keys are on the short side as a result of the Trasuntino's significantly angled gap and smallish wrestplank depth. I elected to use two sizes of weights: one 6 mm wide and 4 mm long, the other 1/4" wide and about 7/16" long, the latter cut by hand from a lead wire several feet long.

First I drilled holes 9/32" in diameter for the large weights, as far back as I could without getting too close to the rack pin:


This took care of the coarse balancing and made the keys back-heavy.

To complete the balancing, I placed a U.S. penny (weight 2.500 g) at the front edge of each sharp and centred on the scribe lines of each natural. This added weight at the front and tipped each key forward again. I then put a small weight on the key and started shifting it backward very slowly until the key just tipped back, as shown below:


I marked the final position of the small weight and drilled a hole for it. A few keys needed more than one small weight, but in the end all were balanced.

Balancing with a temporary weight in front gives a little extra reliability to the return of the keys when released, which will be assisted further by the weight of two jacks resting on their far ends. Some say that this method of balancing also reduces the possibility of an accidental brush of a key triggering an unwanted note, since the keys will require deliberate pressure to respond.

Keyboard: Easing keys

The balance pin holes and mortises are all a little snug at present and the keys need to move as freely as possible without actually being loose, so all the mortises and holes need to be eased to reduce friction.

I used this tapered reamer, which reaches a diameter of 3/32" (matching the balance pins) roughly at its midpoint:


A reamer is a cutting tool and I have previously stated that it isn't a good idea to cut material away when easing keys, in case one goes too far and needs to undo the adjustment. I tried to press the reamer into the balance pin hole from below without twisting it, which would bring the cutting flutes into play. To ease the mortise portion, I put each key onto the leftmost balance pin of the key frame (as shown above) and worked it up and down firmly, letting the pin burnish the mortise sides.

What I'm aiming for is to be able to lift each key straight up on the balance pin and have it slide back down on its own when released. That strikes a good balance between looseness and tightness.

Keyboard: Gluing on sharps

With tilted keys and uneven gaps between keys now corrected, it's time to glue the sharps on.

First I needed to make sure of the final lengths of the sharps to ensure their back ends wouldn't collide with the nameboard when the keyboard was in place. Until now there has been no nameboard, so I went ahead and made one, set the keyboard into the instrument and slid the new nameboard into place. The point was to check whether the front layout line drawn on the key panel (still visible on the sharp levers) aligned with the front face of the nameboard. It did, so I was able to establish a final sharp length, cut the necessary quantity of sharps from my ebony sticks and bevel the front of each sharp at the strip sander to a 10 degree angle.

Next, a straightedge was clamped along the final position of the sharp fronts, leaving a clearance of 1 mm between the naturals and sharps. With a flashlight shining up from underneath the key frame, each ebony sharp was visually centred in the gap between natural key tails and glued down with thick cyanoacrylate glue:


The oily nature of ebony can make it problematic to glue, so the undersides of the sharps were wiped down with lacquer thinner just before gluing to remove any residue that might interfere.

When the glue dried, I put the keyboard and nameboard back into the instrument to see how everything looked:


The nameboard is presently too tall but can easily be trimmed to size later on.

Keyboard: Cosmetic adjustments

I spent a lot of time in August watching the Olympics, but various little things still got accomplished on the keyboard.

Despite drilling the balance pin holes squarely and installing the pins carefully, some the of the keys ended up tilted slightly out of the horizontal, which I think is pretty much normal no matter who is making the keyboard. Correcting this was a threefold process.

First the affected keys had their balance pins tapped sideways with a hammer to bring the key surface level again. However, doing so also moved the key sideways at the same time, creating unequal gaps on either side. That meant the rack pin hole in the affected key end had to be redrilled and the rack pin relocated into the new hole. The new position was about half a hole diameter to one side, which was usually enough to correct the gaps. Sometimes the very back of the key lever ended up rubbing its neighbour after these adjustments, so the rear edge was sanded a little more to restore clearance.

In keeping with historical tradition, I scribed a fine line across the joint between key fronts and backs, and a second line about 4 mm in front of this. The second line will act as a reference point later when the edges of the key fronts are gently rounded over to this mark. These lines are not only cosmetically appealing but also serve as a fine example of our ancestors' tendency to allow construction details to remain visible in the finished product.

Fixing the sharps was a simpler process. First I temporarily laid the ebony sharp caps in playing position and, after a visual inspection, tapped balance pins as above to re-level where necessary. The side-to-side positions of the sharp levers is not that important as the sharp caps are centred at the moment of gluing, but the levers, for cosmetic appeal, shouldn't be any wider than the base of each sharp. I narrowed the sharp levers between the natural key tails by sanding the sides, checking that no wood peeked out when the sharp caps were laid in place. Resetting rack pins was thus unnecessary, and only a little sanding of the key lever ends was required to restore clearances as with the naturals.