Rosewood experiment

[Nick]

Wasn't sure whether to carry this on in the parent topic (viewtopic.php?f=1&t=4424) or start a new topic, as you can see I started a new one! Guess the mods can shift it if they feel it should go into the original topic.
Tom brought up the fact that Somogyi & Overholzer used to soak various bits of guitar in Acetone over long periods of time. Somogyi soaked bridges in an effort to lighten it some by removing it's oily constituants. Overholzer did it to remove resonous materials in an effort to make back & sides resonate easier without the extra weight of the oils & resins. Due to the fact that I work in a chemistry department & have access to the relevant bits & pieces, I thought it would be an interesting experiment to test some theoretical practices. I've started the experiment & must admit that I was mostly thinking of the weight saving side of things so at this stage the experiment is focussed on Ervin's hypothesis. I would have to have some sides or at least take some frequency readings of a bridge blank to look at Overholzer's theories.
I personally only think we are talking milligrams in weight savings but as they say (& I'm an advocate of it), don't knock it until you've tried it
OK so I dug out one of my IRW bridge blanks that I've had in a climate controlled room for around 2 years now. Size of the blank is 38mm wide x 220mm long x 10mm thick. Next I weighed it using a 4 decimal place balance scale.

Bridge on scales.jpg (51.69 KiB) Viewed 16490 times

The weight, as you can see, came in at 75.4817g . I had to stand the sample on it's end, you couldn't get it inside the scale's doors laying down, the scales are so sensitive that even a breeze can change the numbers so they put doors on to eliminate the possibility of this error.
Next I put the bridge blank into a glass "Sandon" Chromatank that has a nice flat lid so as to slow down the rate of solvent evaporation. I also sat the blank on two round pins to reduce the amount of surface shielding of the wood to the solvent. Poured in just enough Acetone to cover the blank (500mls), heres a shot taken side on

Immersed.jpg (43.57 KiB) Viewed 16490 times

.
Not very clear but then the Chromatank never was an optically clear bit of glassware to begin with!

I was amazed at how quickly the colour started coming off the wood, here's a shot taken after the blank had been immersed for less than 30 seconds.

Colour coming off.jpg (44.73 KiB) Viewed 16490 times

Also interestingly enough I was talking to the academic who's balance scales I used & he reckoned that unless the wood is 'just right' the Acetone will only absorb moisture & dissolve the oil from the capillaries of the timber, it's not very good solvent for diffusing across the walls & getting into the cells. He suggested that if you wanted to eliminate resins & oils completely then a short soak in Acetone for a day then swap out to Hexane which can diffuse across the cell walls far easier.

Anyway that's where I'm at so far, it went in at 1420 on the 02/07/12, I'll leave it until the same time next Monday, let it sit in the air for a day or two (we don't want to measure any Acetone still left in it!) then measure it again and let you know how it went.

[jeffhigh]

Maybe let the acetone wash liquid evaporate on a weighed open dish to see what residue is left and how much it weighs.

[Mike Thomas]

There could be a PhD in this Nick.

[charangohabsburg]

Luthieriemyth Buster

I haven't read Overholzer's book but I recently stumbled across a summery of his theories. Scary stuff.

[Nick]

Maybe let the acetone wash liquid evaporate on a weighed open dish to see what residue is left and how much it weighs.

Thanks for that idea Jeff, certainly easy enough to do. I can pour the 'waste' in a dish of known weight when I comes time to refresh the Acetone, & then just let it evaporate off. I guess theoretically the 'new' weight of the bridge after leaving it for a week plus the residue waste should add up to the weight shown in the pic!

Not sure about the PhD Mike And I don't mind a bit of mythbusting Marcus.

[kiwigeo]

For some reason the phrase "micrometering the brick" keeps coming to mind

[Nick]

For some reason the phrase "micrometering the brick" keeps coming to mind

Yeah I'm not sure the results I get render that big a weight loss but as I say I'm open minded & willing to be convinced & I was puzzled by Ervin's theory or whether the benefits he saw were just him being anal.

[charangohabsburg]

Of course, if someone wants to build a precision building relying on "micrometered bricks" he also should measure well the mortar between them!

[Paul B]

Maybe let the acetone wash liquid evaporate on a weighed open dish to see what residue is left and how much it weighs.

+1.

Weighing the residue would probably be more accurate than weighing the bridge. You won't know for sure if you've removed all the solvent from the wood, you might remove resins only to replace them with solvent and see no change in overall mass.

Now that you've already started you can still do both. Weigh the glass thingy with residue in it, and weigh it again after you've cleaned it. Then compare your results with the 'weighing the wood' method.

[J.F. Custom]

Ahem...

You may find you have a piece of Maple in that tank by now Nick

Any news on this experiment?

Jeremy.

[kiwigeo]

I think Nick gave up and went off for a beer.....

[MBP]

Nick,

Any chance you could do another experiment.

I have read on a US site that using oil for a finish adds too much mass to the wood which does not allow it to vibrate.

Could you get a couple of pieces of wood and oil some and then spray or however you usually finish and see how much weight is added?

[Tod Gilding]

That's an interesting one Ro,I havn't heard that,but I assume that it would have to add at least a little mass, but then again that could be used in your favour,maybe Proffessor Nick can investigate this.

[MBP]

Tod,

I was abit surprised to hear it as well considering it was regarding solid body electrics but we will never know unless someone tries. I would but I dont have access to a decent set of calibrated scales.

[kiwigeo]

Tod,

I was abit surprised to hear it as well considering it was regarding solid body electrics but we will never know unless someone tries. I would but I dont have access to a decent set of calibrated scales.

Sounds like a crock to me

[Tod Gilding]

No Marty, This Finish is a Croc

[MBP]

Tod,

I was abit surprised to hear it as well considering it was regarding solid body electrics but we will never know unless someone tries. I would but I dont have access to a decent set of calibrated scales.

Sounds like a crock to me

I agree with you but I still would like to see how much mass difference between lacquer and oil.

[Nick]

Ahem...

You may find you have a piece of Maple in that tank by now Nick

Any news on this experiment?

Jeremy.

Yeah apologies guys, I've been terribly slack......or is that busy? Blue arsed fly territory around here at the moment & so getting the results for this through has completely slipped my mind.
I did actually weigh the blank after a couple of days out of the tank but the numbers were actually higher! (it was heavier than before I started ) so I credited this one of two things either the scales weren't reading correctly to begin with or the Acetone hadn't fully evaporated from within the blank. To this end I sat the blank near a heater for a week then sat it on my bench with every intention of throwing it back on the scales but several events pushed it from my every descreasing memory banks. I'll throw it back on the scales & get back to you with the results.

[Taffy Evans]

Hi all, I have two guitars, acoustic OM in size but not shape. They do have slight differences eg: one cutaway and with a crossed braced back, but otherwise the same. Two major components of the guitars are the same that is that they are built of the same batch of rosewood and spruce. One of these guitars I built 32 years ago and at that time was washing the oils out of the rosewood as per Overholtzers book, the other is in more recent years. I have wondered if the changes in the construction had contributed to the marked difference in tone between the two, or the washing of the rosewood. The second guitar was not treated in any way.

The "washed' guitar sounds far louder, has better string separation , good bass and singing highs, its the clears highs that stand out to me. This thread has set me thinking all over again.