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I have read so many posts on the softness of both KTM9 and French polish as compared to nito that I decided to try an experiment just for curosity sake!! .Though not very scientific it was still informative to me.

I took a a 1/8 dia. steel bar with a rounded tip and dropped it from 3" high on one of my guitars that was French polished, one that had KTM9 and one that was nitro and one that was Catalyzed poly (an ovation). Then measured the dent depth the best that I could. Hear are the non blind results

French polish; .0038 deep dent (5 year old guitar)

KTM9; .0034 deep dent (two year old guitar)

Nitro; .0032 deep dent (3 year old guitar)

Catalyzed Poly (an Ovation); .0022 deep dent I don't remember how old it is the label ha been gone for a while.

Michael, thank you for doing this test. You are a brave man to use your sacrafice your guitars for this.

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Joe Breault
Merrimack, NH
Perpetual novice

Michael, can we assume the same species of wood for the test? One other thing, a lot of Ovations have laminated tops and such, was this one solid or laminated?

Very interesting experiment!!!SteveCourtright38950.6258912037

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"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

Interesting Michael,

Do you have any feel for 0.0006 difference between FP and Nitro Means, what I mean is, is that so small it makes no difference.

I have always come from the school of thought that they all dent in a major collision, and at the end of the day they are musical instruments not display pieces, so a few dents add to the character.RussellR38950.6225347222

as far as wood types they were all Sitka except for the Ovation which I believe to be Engelman.

What this means to me is that even though nitro is harder than FP or KTM9 that dent resistance is not limited to hardness sometimes a softer material will absorb impact with less deformation. like I said this was not that scientific. but confirmed to me that Fp and KTM9 provides IMO as good of protection as needed unless they take a drink of Crown Royal

Thanks Michael

Would you mind repeating the experiment with a 50LB weight and Sunburst Gibson AJ's

No.. well let me think about it ...Still No MichaelP38950.6368402778

If I knew all things were equal I would use my companies Rockwell test meter but there are too many variables to really give a good hardness reading.

Any way to do the same drop test on an unfinished piece of sitka? That might be a good control for further comparison.

I realize that this is not a true test, but interesting nonetheless. Thanks for the post Michael.

BTW, I'm doing glazing sessions on my latest and should be posting some pics soon...looking forward to your critique

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JJ
Napa, CA
http://www.DonohueGuitars.com

Very interesting tests Michael, thanks for not destroying your instruments completely for us!

How did the thickness of the finishes compare. Wouldn't those need to be equivalent.    Four coats of FP compared to two coats or 12 coats of something else? How in the world would you ever determine an equivalency?

Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

I wonder if the dent resistance has any relation to scratch resistance?

Just a guess but I believe each had a film thicknes betweem .019-.024 thick

If the object was to determine which material was the toughest (most dent resistant) then you would do a test with the same film thickness, but here, the object was to test which finish was toughest. Since Michael tested typical finishes that part of the experiment is valid I think.

Using the same substrate would, of course, make the comparison more accurate.

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"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

Steve is right. However the only intent of my test was to se if there was much difference in the typical incidental dent protection of the finishes I do, and to see if I noticed a big gain from using nito over FP & KTM9. Which frankly I did not see that all that much imo. To be accurate I would need to test with all variables other than the finish material, all being equal. but that would have taken a couple months to setup and I would need to repeat the test to average out the uncontrolable variables. Im too lazy to go to that much trouble

How repeatable are your measurements?    
If you had someone else take the measurements, would the get the same results?
If you repeat this with 10 drops on each top, and have you and 2 other people take measurements, on three consecutive days, you'd have something that we could work with.
Sorry, as an engineer that that writes and reviews protocols for testing, I can't help but put in my .02 worth. If one of my technicians came to me with these data I'd tell him that it was a nice initial study, and I'd have write a protocol with 10 drops on each wood/finish sample and I'd probably have it measured by different operators on consecutive days unless the measuring technique was properly validated with calibrated equipment.

How controlled was the 3" drop and how are you measuring the depth?

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

Steve you are speaking with a ME as well and if I took an Engineering approach to my lutherie I would do just as you point out but when I walk into the shop I get into this mode that resembles my mentor (my grandfather) I become a naturalist. I pay attention to the reaction of materials, note how they work but I don't dwell on the physics of lutherie anymore than I have to. For me when working this craft, intuitive thinking is more my key that data based logic thinking. MichaelP38950.7512152778

Perhaps we should build four guitars, finish like Michael has proposed and have SteveS write the protocol and then do the experiment like scientific and all. Remember, each guitar would have to have been played exactly the same number of times with the same song to eliminate that variable.

Now, do we have a volunteer to play "Stairway to Heaven" 1000 times on each guitar???? Don't all speak up at once!!!

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"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

I'v done the latter

Nevermind - just kidding!!!!!

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"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

[QUOTE=MichaelP] Steve you are speaking with a ME as well...[/QUOTE] Oh no, not another one.

[QUOTE] For me when working this craft, intuitive thinking is more my key than data based logic thinking. [/QUOTE] Intuitively, what does your test tell us?
As an engineer, it tells us nothing.
As a naturalist (BTW - what does running around nude have to do with any of this? ) about the only conclusion that can be made is that the Ovation top seems to resist dents more than your guitars.
Can you reasonably conclude anything else?

(I'm not trying to be a pain here. I'm having trouble understanding why naturalistic thinking, if based on poor logic, is worth doing.)

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

Yes I am an old oil fild equipment designer I got my degree From Middle Tenn. State in Murfreesboro Tenn back in 78 passed my board exam in May 80 and have been covered in petroleum ever since Most of my career has been designing pressure vessel production equipment but the last 10years I have been designing down hole and conventional surface pumping units (pump jacks as most people know them). I also have nearly 25 years in CAD and over 20 years of 3d modeling, animation and finite element analysis using 3d modeling and data manipulation.

Though a very simple study I did learn that in a very generalized way that nitro's dent resistance ( as seen in the models I had available) proved not to be all that much greater than the other finishes for the same given impact velocity. True my sample is too small and with too many possible variances to make a definitive conclusion from. but was none the less informative for my general knowledge

based in poor logic? Hmmmm????? That was a bit snippy Maybe so but is satisfied a curiosity for me. Frankly I did not do the test to publish a paper on.

Maybe you are looking to deep for conclusions in my post is the reason you can't see what else I got out of it. After all, for me all it was ever intended to be was a curiosity voyage.

You never know! I just may cut wood in the buff ....or is that I buff cut wood? Hummmmmmm

I really could care less about the fact that you write reviews and testing protocol. I just hope you have enjoyed this topic of discussion and my not always so witty dialogue, and found a chance to giggle with us a little and maybe smell some Rosewood every now and then.

I am sorry but I just can't let my passion for this craft get tangle up in the seriousness that I have to put into my day time career. If I did all the fun would go away MichaelP38950.9993981481

Michael,
I have enjoyed this topic. My apologies for my snippy comment. I did not want to offend you, but after read my post again I can see that it was not written very kindly. I'm sorry for that.

I too have a lot of CAD/3D modeling experience. No animation and very little FEA. I've spent about 30 years designing medical devices and the processes to make them. You or someone in you family very likely has a device that I have developed. The list includes intraocular lenses, coronary and peripheral stents, dental implants, and flow control devices for hydrocephalus and glaucoma.

I too drop a lot of my engineering training when I build.      Sometimes I think what an idiot I am for not being more disciplined in my approach. I then remind myself that I am building for fun and because I love wood and guitar music much more than my day job.

Take care and I am sorry for my offense, please forgive me.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

thank you michael for doing those test, lets face it, its as least as factual as the famous " i pressed my fingernail into it" test .. For me it showed that nitro and fp and KTM9 gave the same results.. plus or minus anything your eye could see ... I would liked to have seen what a raw top result would have been, just for a compare..
Mike

Michael,

Thanks for posting your test results. As you obviously knew from the start, it's not the final word on the subject, but I think it does give us some useful, real-world information to ponder.

Okay, if someone could take the time for the scientific method, this might work (without hurting guitars, and without their inherent variabilities):

Take identical (as is possible) plates of spruce, identically thicknessed (as possible) and identically prepared. Coat each plate with a different finish, to a standard appropriate for each product. Leave one unfinished. Let them cure an equal amount of time in the same environment.

Set each piece on the same surface, apply the same force to each (preferably with a device or setup that takes human error out of the test), and measure each with the same precision tool (again, that mitigates human variabilities).

I think the above would give us usable information. To make the test purer, we'd have to put the finishes on truely identical, manufactured, surfaces and use hardness testers and/or laser measuring devices.

Whatd'ya think? Anything amiss with my reasoning?