Friday, 6 November 2015

Resin cast guitar neck part IV

Undeterred by the setbacks of the previous casting, we were determined that casting a guitar neck has got to be far easier than building one from scratch. Since the whole point of creating a custom guitar neck is to put our "guitar tutor" fret lights behind it, a solid wood neck is out of the question (though it wasn't until we'd already bought a new controller board for our desktop CNC and half-built a milling rig to try it anyway).

Sure, we could probably route some channels in the back, and add some holes in the front and let the LEDs shine through. We could probably even fill the holes with coloured resin and  sand it all smooth - but ultimately it would still look like what it was; a wooden neck with a load of holes drilled into it.

What we were after was a quick and easy way of creating a repeatable fingerboard. Which led us to ask "how hard is cured resin?"

Since the major problem with our last resin casting attempt was the fret wires (the bubbles were also a problem, but that was down to poor application when filling the mould, not because of the actual idea) we started to ponder - what if we cast the entire fingerboard, with the frets as  part of a single-piece of resin?

There seemed only one thing to do; we already had a mould with indentations for frets - instead of putting fret wire in and pouring resin on top, why not just fill the entire mould with resin, and see how it turns out?

Bubbles are a concern, but with a bit of care, we should be able to eliminate them. We dashed off to the local art suppliers and paid through the nose for some "craft casting" epoxy resin and some compatible glass-based ink. We added the tiniest bit of black dye to the two-part resin while mixing it up, then poured it - extra slowly - into the mould.


The whole thing looked like a large inky puddle. But as the resin poured from the mixing tub, we could already see it taking on the slightly translucent, grey-black appearance. If we could shine our LEDs through that, it would look great!

After 48 hours we tried to turn out the mould.


Maybe it was the dye additive (although the craft shop was insistent it was compatible with the - overly expensive - resin kit we'd also bought). Or maybe this particular resin needed more than 48 hours to cure properly. Maybe it's because we didn't add any fibreglass this time. But it was quite alarming when the entire fingerboard bent along with the rest of the mould - similar to how a stick of rock bends after you've sucked one end, forgotten about it, and left it in the window for about eight weeks.

This one was going to take a little longer to cure than our first attempt!


After another two days to cure fully,  the black fingerboard turned out relatively solid. Even after all this time, the "back" (or top, as it was when cast in the  mould) feels a little bit tacky if left in one place for any length of time!

The level of detail captured, however, is incredible.
On our original fingerboard, we'd placed some pencil crosses, as we had originally planned on drilling and CNC milling the actual wood. Not only has the silicone mould captured the grain of the wood on the surface (we're still split as to whether this is Really Cool or A Bit Shite) it even captured the pencil markings (the pencil marks are not gouges in the wood, just very faint lines - almost invisible now of the wooden original).

We're going to have to leave this for another few days to go off fully, before fixing it to a guitar neck and seeing if cast-resin frets are actually playable (or whether they just wear off after a couple of two-step string bends!)