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Hope this subject has not been driven into the ground.  

What is an  ebonized guitar fret board or bridge? 

What wood species were used?

What is the ebonizing process?

What chemicals are used?

I contend that ebonizing cannot force the black color all the way into the wood.  A core sample will show much lighter color on the inside.  

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Not specifically addressing your Q, but ....

On older violins, when ebony was very pricey and hard to get, they frequently dyed different white-wood fingerboards black. They'd even go to the trouble of placing a thin ebony veneer over a poplar fingerboard.

Recently I had to replace a badly twisted ebony fingerboard on an otherwise nice Beard dobro. What I ended-up using was a Richlite® board, purchased from LMII.  It's a composite of about 65% recycled paper and 35% phenolic resin.

It was a new product to me and I was skeptical... but it worked fine. It was stable, consistent in color and the only caveat was to rough-up any gluing surface to about 80-grit before gluing. 

LMII now sells a small sample piece for $1.50... which may be advantageous to have, if only to get "the feel" of it before working it for the first time. 

Ebonizing is a somewhat generic term, it simply means a faux process of turning something Black. It does not apply just to wood, anything that does not start out Black and has a Black finish of some type applied, can be called Ebonized. Stain or paint are common but there are other ways to Blacken wood as well.

The ebonized wood we see in old American fretted instruments can be the same color (dark gray usually) all the way through.  I presume it was a pressure treatment (maple, pear or whatever).  I don't know the chemistry but there's no doubt that the black coloring process can cause the wood to lose structural integrity.  

It's a well known and documented phenomenon, even described in at least one of the old Gibson catalogs.    Gibson was forced to discontinue the practice of using a 1/8" ebonized layer in the laminated necks because so many of them simply split apart.  In that particular catalog the company announced a new neck construction that eliminated the lamination in favor of a black dyed inlay up the back of the neck.   

I presume they abandoned the use of ebonized fingerboards about that same time  (early 'teens).

Gibson did continue using the dyed black wood for peghead veneers, etc.

Replacing an old ebonized fretboard always ends up with hacking the fretboard away with a chisel. The wood is brittle and destroyed by the process. It's black or colored all the way through. I guess it's fruit wood, probably pear wood, with the same kind of tight grain as ebony.

As mentioned before, in woodworking the term ebonizing can refer to any process that makes a pale coloured wood look black.  One of the common methods used is to treat the wood with iron acetate.  An ‘ebonizing solution’ is often made by putting iron (a fistful of steel wool, or a handful of nails/screws) into a big jar of vinegar.  Give it a week or so for a lot of the iron to dissolve into the acetic acid.  Then paint this solution onto the surface of your wood, or immerse smaller pieces in the solution.  It will produce a colourizing reaction in the wood almost immediately.  But it only works in wood that has a significant amount of natural tannin.  You can enhance the reaction if you add more tannin by pre-soaking the wood in strong black tea (not that insipid herbal stuff).  Some timbers don’t react well because they lack sufficient tannin.  Even in the ones with good reactions, it is always only on the surface.  It will not penetrate more than 1mm or so.  You need to shape and finish sand your piece before you apply the ebonizing solution.  If you sand it after treating it you will easily sand through into the pale timber underneath.  But then you can just reapply your ebonizing solution and it will go black again.  It is a very satisfying trick.  

Here is the neck of a bouzouki which I ebonized with iron acetate.  The timber is Australian blackwood, which has high tannin content (before ebonizing it was the same golden colour as the body of the instrument).

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Good timing! Three days ago I started to reset the neck on a 1920s Lyon&Healey parlor guitar.  The fingerboard was dyed and had significant fingernail divots.  When trying to lift the fingerboard extension over the body, the wood simply crumbled.  What was interesting was that the wood under the MOP was light in color, and much more tightly attached to the neck. 

On closer inspection, the wood under the round MOP dots was the same as the rest of the fb.  The wood under the larger diamond shaped inlays was in fact different wood.  It looks as though the diamond shaped inlays were cut out all the way through the fb, and then a diamond shaped filler piece added to bring the MOP level with the surface.  I can see how with mass production, this may have sped up the inlay process

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You may have the right stuff -- err wood -- here.  Might you consider sending me several chips?  I can perform a microscopic analysis and possibly figure out the species.  I can send a shipping address if you are interested.

Many thanks to all for the responses.   I am still hoping to learn specific chemical details, pressures and temperatures used during ebonizing if any.  I apologize if this is belaboring the point.

From my observations, there appears to be at least two kinds of dyed fret boards.   The version shown in the attached image is rock hard, very strong, with consistent color through and through. I know this because I took a core sample from underside of fret board extension.  The extension was easy to heat and remove from the guitar top with no smell, no fumes and no chemical sweat from 200 degree heat.  I hesitate to call this ebonized.  It works and looks like some kind of very poor quality ebony.

The second type of ebonized fret board is possibly just dyed and not ebonized.  These are made of a soft open pore wood which I guess was chosen for dye acceptance.  These boards degrade drastically under heat and just fall apart during removal.  Color is not consistent throughout.  Wood is a little like cardboard and splits very easily.  I think this stuff is charred during the heat and dye process which is probably the cause of breakdown.  I am very familiar with pear wood which I use in furniture making.  Pear accepts dye like crazy.  I am not sure of this at all since microscopic examination tells me nothing. And yes I do have a lab quality microscope.  

Is there a third type that anyone has noticed?  Let’s document more versions.

-Dave

I bought this book.  It is a very valuable resource.  

https://www.booktopia.com.au/art-of-coloring-wood-brian-miller/book...

Many thanks for the suggestion. However, the Miller book covers maple, white Oak, Mahogany, Walnut, Cherry and Alder. None of these woods can be through and through dyed, which is the goal of ebonizing if I am not mistaken.  I don't believe even the most rigorous ebonizing can color a 1/4" thick fret board made from those woods.  

I humbly yield to better informed writers. 

The problem Harmony and many others were trying to solve was fret board wear through caused by pickers with long fingernails. Staining as covered in Miller's book is mostly a surface treatment not penetrating below 1/32" on a surface not subject to wear. Simple dying cannot prevent wear through which makes an otherwise decent guitar look awful and makes the brand name look awful too.

In my opinion, ebonizing should be defined as through and through or deep penetration wood coloration caused by heat and pressure.  I may be completely mistaken.

There are considerable variations in the fret board wood darkening processes.  They used everything from furniture style staining to serious high pressure heated dye impregnation in a retort.  Possibly the image associated with this article shows an example of retort based ebonizing.

One version of an ebonized (maybe) fret board was frequently used on Harmony made classical guitars sold under several brand names.  I would very much like to learn what species of wood was used.  This is the stuff that falls apart like wet cardboard when removal is attempted.  My first guess is Holly.  It absorbs dye amazingly well and to good depth.  However, the fret boards I have worked with are medium to dark brown in the center. Holly is white.  I know because I have the chips.  Also, Holly is nowhere near hard enough to hold frets. Also, can you imagine making thousands of fret boards from relatively rare Holly?  Fruit wood is mostly available in small pieces appropriate for saw handles. My second guess is Walnut.  It accepts dying very well and is hard enough to hold frets.  The question is, does Walnut degrade to a cardboard like mess under high heat and pressure of a real ebonizing process?  I don't have a retort so can't experiment.  

I have a lifelong in depth familiarity with all domestic and many tropical hard woods.  At this point I have no clue what wood was ebonized as defined above.  I am stumped, as they say.  

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