Finish for fretless acoustic bass fingerboard

[Peter Wilcox]

I'm a complete novice at finishing. Sorry if this has been discussed before in detail (point me to links, please). The fingerboard is a relatively soft wood, Peruvian walnut (bad choice, I know), so I need a hard finish for it, especially if I use round wounds. Considerations so far include epoxy (System 3 T-88 ?), CA, something called Envirotex Lite (a two part resin and hardener), or ??

I've already disastrously tried hardware store 5 min epoxy glue (my local store here in the boonies doesn't stock longer setting ones), which 1) I was unable to apply evenly within the allotted time and 2) did not harden sufficiently in 48 hours to be sand-able without blocking. I have removed it.

I would prefer to brush or wipe it on, rather than pour, as I already have the radius, and if poured level would have to be re-radiused. The wood also has pores, so the finish would need to fill these - I'm unsure the CA would work, though I could use a gel preparation for the initial coat.

Any suggestions, links, or experiential stories appreciated.

[Barry Daniels]

Something like West Systems epoxy works good. It wipes on easily and it cures very hard. I found that it was harder than CA.

[Beate Ritzert]

I would use Polyurethane lacquer on the fingerboard. Several layers with sanding in between. Much easier to apply than Epoxy and more or less unvisible. I did that a few years ago on the rosewood fingerboard of a cheap vester witch bass, and it works great.

[Peter Wilcox]

Thanks Barry and Beate

Barry - Is the West System fairly liquid (not viscous like epoxy glue)? Do I use several coats, sanding in between? I assume this is the 105 resin and the 205 or 206 hardener. Can I buy it in quantities less than a quart - if so, where?

Beate - How durable is the polyurethane? - I would worry that the attack of the round wound strings over time would damage the finish and the relatively soft wood underneath.

[David King]

Peter, I think you'll want the 105 & 207, West systems "finishing" epoxy, if you can swing it. Try Aircraftspruce.com if you're on the west coast.
It rolls or brushes on nicely and the bubbles will pop without too much effort. It's an exceptionally hard epoxy that's also very easy to sand.
You can find pints for sale if you dig around a bit.

Polyurethanes are very tough but much harder to sand. They'll take longer to set up than the epoxy and require more coats. I like the MCUs (moisture cured urethanes) which are used for gym floor refinishing and stink to high heaven. Hard to find in small quantities but you can get small bottles of U40 Permagloss.

[Barry Daniels]

I buy West Systems at a local boat parts supplier.

[Brian Moum]

Peter - the 207 is the special clear-coat hardener. 205/206 will both cure clear but may have a slight yellow tint - the difference between those is working time. I use all three (sideline gig as a composite boat builder): 205 = fast cure at normal temps and will cure slowly in low temperature; 206 = slow cure at normal, will work at elevated (80-90F +). The 207 is basically the 206 but a cleaner finish.

They all cure hard, are mostly self-leveling, and can be brushed or rolled on. Just don't let it sit in a deep pot - thin film is your friend. In large lumps, it heats up and kicks quickly.

You can buy it in smallish quantities: just get the resin and hardener at the same time. Smallest you can get will probably be a quart of 105 and a pint of 207 (some boat shops sell smaller repair-kit sizes). The pumps that come with them are sized for the containers to ensure correct proportions - can't swap pumps from pints to quarts, for example.

[Beate Ritzert]

The Polyurethanes indeed needed several coats with sanding in between. Dependent on the solvent they are pretty tough - the fretboard of my witch does not show any marks of the strings (GHS pressurewounds - even these cut into the rosewood)

[David King]

The most common mistake inexperienced folks make with any epoxy is to not take the time to mix it thoroughly. Mix one oz in a clear solo cup with an L shaped or T shaped piece of wire (one that = the diameter or radius of the cup's bottom) using a cordless drill. Keep the wire totally submerged so that you don't draw air into the mixture. Run the drill at low speed for 2 minutes and then wipe down the sides and the bottom of the cup with a wood spatula. Pour that mostly mixed epoxy slowly into a second cup and repeat the mixing. Wait a few minutes for any the bubbles to come to the surface.

I would preheat the fingerboard with a blow drier and then pour out the epoxy along the length before brushing it out. I usually make a dam of masking tape around the whole perimeter. You would probably read this post starting at the end and working backwards.

[Peter Wilcox]

Thank you all for your responses. It looks like the West System would be the easiest way to go, but I can't justify spending $60 for the $2 worth that I need. I'll go with the multiple coats of polyurethane. The instrument is an experimental learning experience anyway, and so I will learn.

[David King]

Peter,
I hear you! It would be wonderful if West Systems would make single use foil pouches. Some epoxies do come this way.
I've used west systems for a host of other finishing projects including a large round dining room table, a butcher-block kitchen island and wooden dish drainboard.

If you're of an experimenting nature you could try this stuff: http://www.solarez.com/productsnew/zerovoc_pint.html

[Michael Lewis]

All this energy spent, and you will still have a soft fingerboard. Would you not agree you would be farther ahead if you were to change out the fingerboard for a harder one?

[Peter Wilcox]

Michael, I agree that would be the optimal way to go. However, this instrument (and another I am building concurrently) is my first acoustic build, and has numerous flaws already. It's not worth the effort to correct - at this point I just want to put a hard protective layer over the wood to help it last. If the finish penetrates the wood somewhat, this seems like it would be at least partially effective.

I'm only going to use it for bluegrass, so looks and tone are not very important.

[Bob Francis]

Peter
I sent a link to a decent tutorial from another site. Not sure if I could link here.

Bob

[Peter Wilcox]

Thanks, Bob, I got the link. That looks like what I had in mind, but not sure of the properties of the epoxy he used (SystemOne Bartop epoxy.) There's some Envirotex Lite I was considering at my local hardware store that may be similar.

However, I've already started the Polyurethane process, so this will have to wait for the next one, but thanks again for the the link - it's bookmarked.

[Greg Robinson]

Bob, link should be fine (there are some caveats about directing traffic to other forums in the rules if you want to check).
Feel free to post it.

[Bob Francis]

http://badassbassplayers.com/forum/view ... 53&t=17116

Thanks Greg! Here ya' go.

[David King]

Five different chemical washes and 10 coats of epoxy? That's going a bit overboard (read utter nonsense) but undoubtedly folks will read that on the web and believe it as the gospel truth. I hope common sense will prevail around here.

[Greg Robinson]

I'm with David.
He goes through 5 different chemical washes to "ensure there are no contaminates", and then immediately contaminates it again by sanding?

[Bob Francis]

I suspect those are some of the gidderences between builders and do it your-self modifications.