I've been making banjo bridges from Bog Oak (imported from Europe / purchased on eBay + other places) but now am having a difficult time sourcing this and I'm trying to come up with an alternative. This led to experimenting with Thermally Modified oak and trying to darken it.
I'm sourcing the thermally modified oak from Fallen Lumber in Arbutus, Maryland (local to me) and they allow me to search for the quarter sawn pieces in the stacks. I'm further trying to get the dark color that bog oak has. From what I have researched, this is mostly due to iron from the peat bog reacting to the tannins in the oak. This led me to the "ebonizing" wood topics which use Iron Acetate (steel wood dissolved in strong vinegar) to color the wood dark. People doing this are also often adding tannic acid (tea bags and other sources) to the mixture to get a blacker color. This led me to try using Ferrous Sulfate to darken the thermally modified oak.
Since I'm using a CNC router to cut the bridges / fretboards, I need them to be black all of the way through and not just dyed on the surface. To accomplish this, I'm using a vacuum chamber with the blanks submerged in the Ferrous Sulfate solution which seems to be getting really good penetration. I pull and release the vacuum a couple of times over a few minutes which seems to push the solution into the wood then I leave it overnight to allow the reaction to work.
Here are my results so far. The small piece is Bog Oak, the larger piece is my experimental thermally modified oak. The 2nd photo shows the larger piece cut in half to show penetration.
And, yes, I realize that I'm unlikely to duplicate the process since bog oak takes 1000+ years to happen but I'm trying to come up with a reasonable substitute that is locally sourcable and affordable.
Yup, lots of fun trying "outside the box" stuff. Maybe consider soaking your wood in India ink? Ferrous sulfate, nasty stuff that might take special requirements to dispose of...
My thinking is that India ink would possibly bleed onto the banjo head if I made a bridge from it. Have you used it before as a wood dye? Is there some fixing agent like is used for fabric dyes?
My next experiment is likely to either add tannins to the solution or possibly treat the oak with tannic acid before doing the Ferrous Sulfate treatment
Also, I think that I can just dump the used Ferrous Sulfate in the yard since it's also sold as a fertilizer at local home stores.
quote:
Originally posted by Cockrum_StudiosMy thinking is that India ink would possibly bleed onto the banjo head if I made a bridge from it. Have you used it before as a wood dye? Is there some fixing agent like is used for fabric dyes?
>>> No, I haven't but a coat of teak oil + buffing will seal it nicely. Why not go with a dark, or black wood from the getgo?
Also, I think that I can just dump the used Ferrous Sulfate in the yard since it's also sold as a fertilizer at local home stores.>>> My bad, I confused that stuff with ferric acid.
I don't know of any other black woods that are of the appropriate density to make a banjo bridge. Ive tried many (30+) different woods for bridges while experimenting. Bog oak and thermally modified oak sound really good in a bridge but people seem to really like the black color of the bog oak which is what I'm trying to replicate.
Have you tried Exotic Lumber near the bay bridge? If you ask, they may be able to source some for you, hopefully at a reasonable price.
Edited by - reubenstump on 05/13/2025 03:10:40
I have used India ink on a fretboard. Just wiped it on and wiped off excess. To mitigate it bleaching into the head, you could lightly sand the bridge feet to remove some ink. Also letting it dry for a good period. Also seal with a light coat of a sealant
I buy lots of stuff from Exotic Lumber - they even posted a photo of some of my stuff on their page. I get ebony cutoffs from them for the bridges tops.
I really want to avoid India ink because of the mess, extra finishing steps, and likely effects on the sound/weight.
I'm making these in quantity so extra steps are an issue.
There is lots of Bog Oak around here. We even have a couple of big logs here, over a ton combined. The locals almost revere it but I’m not a fan of just sticking it in the garden.
quote:
Originally posted by martyjoeThere is lots of Bog Oak around here. We even have a couple of big logs here, over a ton combined. The locals almost revere it but I’m not a fan of just sticking it in the garden.
You know anybody that wants to ship some to Maryland, USA? I need to end up with quartersawn pieces 3.5" x 0.75" x 0.375"
quote:
Originally posted by Cockrum_Studiosquote:
Originally posted by martyjoeThere is lots of Bog Oak around here. We even have a couple of big logs here, over a ton combined. The locals almost revere it but I’m not a fan of just sticking it in the garden.
You know anybody that wants to ship some to Maryland, USA? I need to end up with quartersawn pieces 3.5" x 0.75" x 0.375"
I don't know much about the market for it. It's considered by many to be precious. You see it a fair bit as center pieces in gardens but it doesn't do anything for me. I make my bridges from bamboo because I think Irish guys would take a dim view of using Bog Oak but I'll make some enquiries.
Here’s two logs outside the house, probably enough for a few thousand bridges and there's another one inside the house.
