Fretless epoxy woes

[Jools4001]

I have a 5 string fretless with a rosewood fingerboard that, after 10 years sterling service wearing roundwounds the whole time, has finally developed grooves in the fingerboard that are big enough to need sorting out. I thought that I would kill two birds with one stone since I've intended to epoxy coat the fingerboard for a good while.

Although I've never done this before, I have worked with epoxy and resins on my motorcycles, I've read through all the relevant epoxy threads on here (several times) and since I'm usually very adept at working with my hands at cabinetry, doing setups and minor repairs to all my basses for the last 30 odd years and have even scratch built a couple of playable, but not particularly inspiring basses many years ago, so I felt confident enough to give it a go.

I cleaned the fingerboard maybe around 10 times over a period of a week or so with methylated spirits to degrease and clean it, and again before I applied the epoxy (yes, I did make sure it had all evaporated before applying the epoxy)

I decided to use the 'dam and pour' method, so yesterday I taped up the finger board, leaving the tape around 1/8th proud. I knew this was going to be more laborious when it comes to applying the 12" radius block to it because I will have to sand down the thicker edges, but it also guaranteed that the underlying grooves would be filled.

I used West Systems 205 epoxy and 205 hardener which I mixed in a brand new tinfoil container using a disposable plastic teaspoon. As in the instructions I mixed 10 teaspoons of resin with 2 teaspoons of hardener for a 5:1 ratio, and I also added 5 drops of Castin' Craft black epoxy pigment (because I want a jet black fingerboard) - I actually used slightly more hardener to compensate for this - not much, just letting the teaspoon overflow a little before adding it to the mix.

I had already done a test mix and found that the 205 is not very viscous, so I kept stirring the final mix gently but thoroughly, making sure not to produce air bubbles, for around 10-15 minutes until the mix had started to gel a bit and had become about as viscous as thick treacle.

Then I poured it on, spread it about very gently with an old credit card until there was a nice thick even coating. After around half an hour I had just a few bubbles appear (5-6 of 'em) so I just wafted a blow torch (set with a yellow flame) over them and they all disappeared almost instantly.

It looked very encouraging, a nice even piano black finish with no blemishes, hair or dust entrapped, I was expecting the epoxy to flow somewhat so that it was as flat as a mill pond within it's dam, thinner at the crown of the fingerboard radius and thicker at the edges. That's what I got so I left it at that. Didn't touch it at all for another 24 hours.

I've just come to inspect it and, although I don't intend to sand it down until next weekend, I'm very disheartened. While it is exactly the same as I left it for the most part, the epoxy is still as soft as tar on a hot day - despite the instructions stating a working cure in 7-10 hours. It's been sitting in my dining room which is a steady 21 degrees (68F) and the humidity in the room isn't anything to worry about.

I can't for the life of me work out what I've done wrong here. Cleaned thoroughly, correct ratios etc...the only thing I can think of is that the 5 drops of pigment may have screwed things up. Any ideas? Do I just leave it and hope it cures or do I reconcile myself to scraping off the whole sorry mess and starting again?

 

[Hopkins]

Give it a couple of days and see if it hardens.

 

[hover]

Probably in the thickness you've poured it needs a bit longer to set up and cure. I wish you luck with this.

 

[Vincent P]

Let it sit, even if it goes the week. Agreed it may just be the thickness of pour.

 

[tjclem]

Any way you can get some sun on it? I know you are in the UK but it can't be rainy all the time?

 

[powerbass]

you might want to contact west systems directly for tech help. west systems epoxy sets up even quicker when it is applied thicker - heat is generated when it starts to set - keeping the glue mixing cup in the refrigerator is a common way to slow the set off.

 

[Jools4001]

Any way you can get some sun on it? I know you are in the UK but it can't be rainy all the time?

Ha ha...Last year, on October 1st it was 30 degrees Celcius here (86F). Today it feels more like 30F - it's not really, it's low 60's but it's now dark, damp and feels chilly.

you might want to contact west systems directly for tech help. west systems epoxy sets up even quicker when it is applied thicker - heat is generated when it starts to set - keeping the glue mixing cup in the refrigerator is a common way to slow the set off.

Yes, that's what I thought, it's an exothermic chemical reaction so it shouldn't matter how thick it is. When I've used glass fibre resin or epoxy adhesive in the past, the reaction has sometimes been too hot to touch if you lhave any appreciable amount left over in the mixing tin as it starts to cure.

Anyway, after another 12 hours i think it's curing a bit more - it's just taking a lot longer than expected (or stated). I'm using the couple of teaspoonful's that I had left over in the mixing tray to judge what it's doing. I'll leave it until the weekend, it's got two chances; it'll either be cured or it won't. If not I'll be stuck with the same job of scraping it off that I would have right now...but with luck I may not have to

 

[Jo6Pak]

would be great if you could post a few pix, both in-progress and completed. good luck, in any case...

 

[Bruce Johnson]

Was the 205 hardener fresh, that is, a recently opened can? If it's been sitting around a while, like six months or more, with venting to air it will absorb moisture and go bad. When it starts turning a dark amber, you shouldn't use it. When I open a fresh can of the 205 hardener, I immediately pour all of it into a plastic squeeze bottle with an air-tight cap. That will give it a much longer life. Those little pumps that they sell have a vent hole. If you leave the pump in the 205 hardener can, it will go bad quicker.

With that said, I'm surprised that you didn't have the opposite problem of it kicking off too quickly. The 205 hardener is the fast hardener, and it will turn the epoxy into a smoking lump in 5-10 minutes if you leave it anywhere very thick. For casting and pouring applications, I recommend the 206 slow hardener. It's much easier to work with and will normally take 12 hours to cure.

I'd let the fingerboard sit for a week. It may still kick and harden. The few times I've had slow-curing West Systems, it was caused by spoiled hardener.

By the way, the best pigment I've found for making West Systems black is Moser's alcohol-based aniline dye powder. It's a powdered dye that's made to be mixed with alcohol to make a black stain. But if you just sprinkle a bit of the powder in the epoxy, it gives a deep opaque black and doesn't interfere with the epoxy's chemistry. There's a possibility that the dye that you used had too much solvent, and weakened the hardener. But if it was listed as being suitable for epoxy, that shouldn't be the problem.

 

[Jools4001]

would be great if you could post a few pix, both in-progress and completed. good luck, in any case...

I would love to, unfortunately our camera went missing a month or so back. I know we packed it after visiting our daughter but can't find it anywhere now that we're home. I'm also a smart phone luddite, my cell phone does calls and texts.

Was the 205 hardener fresh, that is, a recently opened can? If it's been sitting around a while, like six months or more, with venting to air it will absorb moisture and go bad.

I think you may be onto something there Bruce. West Systems products are not that widely available over here. I decided to track some down because a lot of folks on here use it and it was easier to try and find some than research an untried 'local' epoxy. I sourced it from a boat chandlery that sells stuff to the inland waterway market, so who knows how long they'd had it in stock, and since they're based at a marina there's probably more moisture in the air. It came in an unopened pack but the hardener was definitiely starting to amber, not violin rosin type amber but definitely a lager beer colour.

Can I also say, sincerely, that having read through your enlightening article on luthiery economics I am very humbled that you would spend your time trying to help out a complete stranger like me....

Anyway, 3 days in and the epoxy is finally hardening across 95% of it's area (using the thumbnail test on the little meniscus ridge where it meets the tape). The only bits that I'm concerned about is that there is a thumbprint sized patch roughly under where the F# on the D string would be that still appears a little gloopy, and there is another similar gloopy piece that looks like somebody has dug their thumbnail into it around the second octave of the G string.

I will give it a few more days and see if these little patches are still troublesome at the weekend, if so I'll scrape them away and drop fill them, then leave the thing another week...I'm in no hurry, just want to get it right, which is why I'm a bit gloomy that after bordering on OCD with degreasing the fingerboard and being very careful to mix the epoxy thoroughly I'm getting this inconsistency. I really thought that the epoxy curing would be the least of my problems.

Thanks to everyone for your replies so far...I will get there... even If I have to sand the whole lot off and start again.