Regal Banjo 'Mother of Toilet Seat' Refret

June 03, 2016

Regal Banjo 'Mother of Toilet Seat' Refret
A refret is a serious undertaking on any instrument. On some vintage instruments, however, there are factors at play that make an otherwise routine job far more complicated. This late 1920's Regal tenor banjo has what is affectionately referred to as a 'Mother of toilet seat' fingerboard. The fingerboard itself is maple, but it's overlayed with pieces of faux mother of pearl made from celluloid, a somewhat primitive and rather unstable plastic. In most cases, an instrument owner may elect to have a refret done once fret wear from string contact is so severe that a simple level and crown job will not be possible. On this instrument, however, the refret is necessary to correct damage caused by the celluloid overlay.

Over the years, the celluloid started shrinking. This instrument likely also spent a number of years in a hot dry attic, which caused the glue joint between the fingerboard and neck to creep and give way.

Eventually, the celluloid shrank so much that the fingerboard beneath it cupped, causing frets to work loose. In most instances such as this, frets are pulled, a rosewood or ebony fingerboard is planed flat, and then the frets are replaced. In this case, the celluloid will have to be removed as well.

The back of this instrument has also started to come apart. Same problem here, although the back reglue was far more straightforward, and didn't require the whole thing to be dismantled and pieced back together. I also fabricated a new bridge, and overhauled the setup on this instrument, but in this blog post, I'll focus primarily on the work I did to the neck and fingerboard.

I usually apply heat to each fret with a high wattage soldering gun, before pulling them loose with a pair of flush ground end nippers. The heat helps prevent the fingerboard from chipping and splintering as the frets are being pulled out. Celluloid dinitrate is extremely flammable, so I didn't heat these frets before pulling, and honestly, it wouldn't have been necessary to do so. The severely cupped fingerboard had worked most of the frets loose already, and the celluloid overlays would have supported the wood next to the fret slots enough to prevent chipping. These frets practically fell out; in fact, a few were already missing when the instrument came into the shop. This was by far the easiest time I've ever had pulling frets. Definitely not a sign of things to come though. 

Next up, the binding is removed. I work slowly with an xacto knife to loosen the binding, starting at the heel, and working my way up to the nut. The binding is very brittle and fragile, but it popped loose from the fingerboard easily without being damaged in the process. 

When this neck was made, the celluloid was likely glued to the board in one piece, and the excess was trimmed flush. The fingerboard would have been slotted afterwards. You can see in the above photo, there's some continuation to the pattern in the fingerboard from piece to piece. After pulling both binding strips, I took a second to clean most of the finger gunk off of the celluloid before removing it.

The celluloid overlay pieces are about .020” thick, but not nearly as brittle or fragile as the binding. I use a chisel tipped hobby knife and a painters palate knife to work each piece loose, starting from a corner. 

The binding and celluloid is set aside on a piece of Plexiglas, and each piece is kept in the correct order and orientation, so there won't be any confusion when it comes time to glue them back on.
Now it's time to pull the fingerboard. I use a Sealector tacking iron to apply heat in order to loosen the glue joint, and then I use the same palate knife to slowly work the board loose. I also have a few putty knifes that I've ground down and beveled to be better suited for this task. 

Here's a shot of the fingerboard, removed, but still sitting in place. This photo gives you an idea of how badly warped the thing was. A thin piece of veneer was sandwiched between the board and the neck, and that's visible in the photo above as well. The piece of veneer came apart during the fingerboard removal, and I elected not to replace it. Next, I'll use vinegar to loosen and remove the remaining glue residue and tape that was used to mount the celluloid. 

In this photo, I've heated up the fingerboard and clamped it flat to my bench, underneath a fingerboard leveling beam, in an effort to flatten it out most of the way.

Here are a few more shots of the fingerboard, part way cleaned and prepped for install, along with the celluloid and binding strips. 

After the board is cleaned, I check the depth of each fret slot with a handy little tool made from a piece of scrap fretwire with the barbs filled off of the tang. If I'm not able to seat this piece of wire, I'll clean and deepen the fret slot with my fretting saw.

Next, it's time to glue the fingerboard back in place. I position the binding strips in place, and clamp the fingerboard to the neck without glue, ensuring that everything lines up neat and tidy. Then, I drill a tiny hole through the 1st and 10th fret slot and into the neck, and I fit a thin wire gauge nail into each hole. This will prevent the fingerboard from slipping around during the glue up.
Finally, after a few more dry runs to check for alignment and other problems, I glue the fingerboard back in place using Titebond, and clamp it firmly. I wait a half hour or so for the glue to set most of the way, and then pull the nails out of the fret slots and clean glue squeeze out from the binding channels. Then I leave it all clamped up overnight. After the clamps are removed the following evening, I go over the fingerboard quick with a hand plane and a leveling beam to ensure it's perfectly straight and flat.

Now, it's time for the monumental task of gluing each piece of celluloid back on. To keep the overlays perfectly aligned, I clamped the binding strips in place temporarily to limit side to side movement. I also used a few pieces of fretwire with the barbs filed off of the fret tangs to sit in the fret slots on either side of the piece being glued, to keep them firmly in place. I made a cork padded caul to cradle the underside of the neck, to prevent the clamp from marring it up, and I used a second caul to press each celluloid piece firmly flat against the fingerboard. For each piece, I shortened the caul to fit between the fret slots. After about fifteen minutes or so of being glued and clamped, I'd remove the binding strips and fret wire bits, and after another half hour, I'd remove the clamps, and glue up the next piece. 

As you can imagine, this took a very long time. I did this over the course of almost two weeks while working on other projects during the wait time. In the above photo, you can see that as the heel of the neck tapers up, I no longer have a flat surface to register the clamp against, so I put a length of dowel in my drill press, clamped the neck firmly to the drill press table, and then cranked the table up against the length of dowel to apply clamping pressure. I clamped up the last seven or so pieces in this manner.
Here's a close up shot, showing how perfectly everything has to be lined up. If there's a gap on one side, it's going to be hard to get the binding to go back on cleanly.
After the celluloid is all in place, the fret work begins. I squeeze titebond into each fret slot, hammer a length of fretwire in after it, and then clip off the excess with my end nippers. As I go, I check each fret with a fret rocker, to make sure they're all level with each other, as I like to minimize the amount of fret leveling I have to do afterwards. Finally, I remove glue squeeze out with a vinegar soaked q-tip.

Here, I'm filing the fret ends flush, to allow for the binding to be reinstalled. I'll bevel and dress the fret ends later. 

The binding channels are prepped by carefully chiseling glue residue, both old and new, off of the edges of the fingerboard. The binding strips are prepped in the same manner. The binding is incredibly fragile, and despite my best efforts, I ended up breaking a piece in half while scraping it clean. A seamless fix is possible, however. In the above photo, I've got one half of binding glued and taped. I have a jar of 'binding glue' that I made out of scrap bits of ivoroid binding that I dissolved in acetone. I'll put a small dab of this special glue between the gap where the binding broke, and it'll melt neatly back together. Super gluing the pieces of binding back together would be structurally sufficient, but it would leave an unsightly black glue line. This method fuses the two pieces of plastic back together, and is very difficult to detect. Each strip of binding is glued in its channel with titebond, and held in place with masking tape. Masking tape has a certain amount of elasticity to it; if you lightly stretch each piece before sticking it down, it will actually pull the binding strip tight into the slot. 

After both pieces of binding are fitted and glued overnight, I carefully remove the masking tape. I use naptha to loosen the tape first, to prevent the tape from taking pieces of the brittle 90 year old finish off with it. The minimal amount of binding overhang that we're left with as a result of the fingerboard having been thinned slightly is then leveled down to the fingerboard with a razor blade.

Finally, the frets are dressed. I bevel the fret ends neatly, and any high frets are carefully leveled and crowned. This is far more tedious on a plastic fingerboard; if I slipped with a fret file and marred the celluloid, it wouldn't be as easy to fix as it would be on a rosewood or ebony board. I then go through again and remove any leftover glue residue with vinegar. 

Lastly, the neck is reattached to the body, the (now fixed) back is attached, and the banjo is strung up with nickel wound strings and set up.

Project Complete!

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