Don Noon's Bench 2023 -

[Don Noon]

My old "bench" thread spans nearly 10 years and was getting kinda long.  And I'm a totally rebuilt person now after a year of restoration.  Good time to start a new thread.  The old thread is here.

As a warm-up to get back into making:  a rebuild of my #4 violin from 2010, back when I was using up my bigleaf maple.  I had put in an experimental bar not too long ago, and it didn't do very well, so I wanted to put a normal bar in.  Also, for some reason new makers (as I was at the time) tend to end up with blazing red, thick varnish.  So that had to go.

A comparison of the original and after being stripped and terpene ground:

And final condition, mostly just clear.  Just a hint of reddish:

I think the sound has gotten more powerful; there's still some jumpy notes on the E string which will hopefully smooth out over time.

[MikeC]

Looks good Don but now you got me thinking...  As a new-ish maker I have a nice red varnish that I was thinking of using, now I'm having second thoughts...  

[Shelbow]

I quite liked your original Red varnish to be honest. A nice shade of red, not too intense, not too weak.

[Don Noon]

OK, onward to new instrument work.  Here's the "kit" for my next one.  The only recent work was cutting the corners for the purfling, and gluing it in.  The ribs were done nearly 2 years ago, and the plates roughed out a year and a half ago.  The last 2 years have not been the best, but at least things are looking better now.

[GerardM]

Intriguing form you are using Don, is that your own design?

[Don Noon]

Yes, my design of a collapsable form.

[Liutaio_br]

Hi Don, I'm glad you're back to your jobs, welcome back.                                          If you'll allow me a little hint, to reduce the contrast between the purfling color and the wood color, try using Pear wood for the white purfling.  Cheers, regards!

[Don Noon]

I have used pear purfling before, but I'm liking the white contrast more.  And I bought a ton of the white kind.

[Chris Llana]

I also like the higher contrast better, although in any case, the contrast will be muted after the stain is applied.

[Don Noon]

The recently rehabbed and revarnished #4 from 2010 is now in the hands of a young violinist who seems to have some potential.  See a video here.

Although making instruments for players to enjoy is the main reason for doing this, selling a violin means justification for buying more tools .  This is the new one:

The new violin build is going excruciatingly slowly.  Maybe inertia from the year or so of inactivity.  Or getting old.  In any case, the body is together.  This is an outlier as far as in-process measurements go, with the plates being very light with extremely high taptones (see a separate thread on that topic here.)

[Jay Higgs]

Very nice, Don!  Is the wood color then natural of your torrefied wood?   What will you use the plane for?  I have the exact same one but am a bit unsure about when to use the low vs high angle plane in violin work.  

 

[Don Noon]

Jay - Yes, that is the base color of the wood, nothing added.  The plane is a replacement for an old-ish Stanley, and used for odds and ends, like planing bass bars to the right width, trimming ribs, squaring blocks, and small stuff like that.

Good bump to remind me to get back to the shop, as I have done nearly nothing for the last month and a half.

[Don Noon]

Here's the 12-year old owner of the rehabbed violin #4 that I show in the first post of this thread.  He's petty good, and has the facial espressiveness of a pro.  

Meanwhile, back in the shop (where I'm seldom found lately), I have found tangential projects to keep me from making progress on actual instrument making.  This time, it's making a tool to make tools to make violins... a jig to hold chisels and plane blades for sharpening on a diamond disc machine that I cobbled together a few years ago.

The rosewood cross-slides keep the blade in a repeatable orientation to the disc.  I won't be using my wheel grinder much any more, as the diamond is faster, doesn't burn the blade, and I can change grits in a few seconds.  BTW, the skew chisel is for cleaning up the pegbox wall around the A string.

[GeorgeH]

That young violinist sounds great on your fiddle, Don!

[dan gall]

Long time listener, first time caller.  I greatly appreciate your approach to materials science and lutherie.  So much so that I am in the midst of a 36"x12" tri clamp pressure vessel build to enable me to process cello tonewood.  Sadly, cello wood won't fit in paint buckets or other low priced pressure vessels.  I had taped it in anticipation of using a spray varnish, but the operating temperature of that product is too low.  Onwards to Kapton to insulate the Kanthal A1 ribbon that will form the heating elements.  I plan on more Kapton on top of the Kanthal to reduce electrical shock hazard.  I've also ordered some "eco" ceramic wool insulation which I will make safe(r) by treatment with colloidal silica delivered by water spray and then heated to fuse the wool to itself.

I have some test wood, but if you're willing to part with some more information on your process, I'd appreciate it.  You mention anaerobic steam as the environment.  Do you use a nitrogen flush or vacuum to remove oxygen?  Do you add water to supplement the water that is released by the wood?  Do you have time/temp/pressure ramps/profiles you'd be willing to publish?  Does viola wood require any changes vs violin wood due to added volume? Thank you for any knowledge you're willing to share and I apologize for being so forward.

Dan.

[Don Noon]

Hi Dan,

Sounds complicated.  For heating elements, I used silicone strip heaters I got off eBay.  Easy.  Cheapo fiberglass insulation.  I remove the oxygen with a vacuum pump, then let the bound water in the wood pressurize the chamber during heating.  There's a lot of water in wood, and I have to bleed it off to avoid overpressurizing.  With my 200W heater and chamber +wood mass, it takes abot 8 hours or more to get to where the heat and pressure need watching, which allows starting before going to bed and having things near operating temp in the morning.  Viola wood or violin wood gets the same treatment; the processing is so slow that I don't think the thickness makes much difference.  I can't speak for cello wood.  A fully loaded chamber is slower to heat due to the mass and extra water involved.

These are just the things I settled on for my processing; others will almost certainly do things slightly (or hugely) differently.

[dan gall]

Don,

Thank you for replying at all, and so quickly.  I hope I haven't distracted you from anything important.  My build is a bit complicated, but is also cost focused given the dimensional requirements.  I think it'll be best if i save the full exposition for another thread documenting my search for products, the build itself, and process characterization and optimization.

The short version is that paint pressure pots tend to not go deeper than 26.5" and cello wood is a bit over 30" long.  Custom pressure vessels are $$$$$.  Tri clamp is modular and only a little more expensive than a modest new 5 gallon paint pressure pot from a reputable company.  The only other option is waiting for a used custom vessel that meets all the required dimensions and pressure rating to become available for an affordable price.

I've designed my heater to be about 1400W, but plan on adding a power transistor circuit and a potentiometer and/or transistor-resistor ladder to enable energy conserving manual/programmable reduction in output heat.  The 500ft of Kanthal A1 was $37 so not doing too badly on cost.  and off-brand polyimide tape is cheap also.  I almost went with fiberglass, but didn't want to under-specify it.  I have some fiberglass lying around so I may go with that too.  I am interested in making a kiln/refractory, so getting experience working with refractory materials is a bonus.

I definitely have a pressure relief valve in addition to the needle (manual pressure relief) and ball (vacuum line shut off) valves.  The one I went with is 150PSI but if necessary I'll put in a 175 or even 200, despite the 12" tri clamp system being rated for 175.  If I have to exceed the rating I'll proof test it in an unpopulated area to another 10%, so 220 PSI, per ASME.

 

 

[Don Noon]

I wouldn't go over 50 psi.  It's not necessary for wood torrefying, unless you want to do something more exotic.

[dan gall]

Don,

Thank you again for your time and advice.  I specified a somewhat more capable system than a paint pot because I didn't know what pressure/temperature regimes you used and because pressure is very non-linear in temperature for saturated steam.  I also inferred incorrectly that torrefaction's etymology was related to pressure from the torr unit of pressure.  I also read of your experiences with toasting wood too thoroughly and postulated that higher pressure at lower temperature might solve some problems.  We'll see!  Exciting times!

[Evan Smith]

This looks like a recipe to separate wood into gas and carbon.

Probably makes a very dark sounding extra lite fiddle.

[dan gall]

18 hours ago, Evan Smith said:

This looks like a recipe to separate wood into gas and carbon.

Probably makes a very dark sounding extra lite fiddle.

At risk of being accused of not getting the joke, the objective is to use accelerated aging techniques to produce wood similar in properties (dimensional stability, sound, etc) to old instruments that we know to sound good.  It is also to reduce musician surprise that their 10 year old instrument gradually started sounding worse due to being in an early stage of the aging process.  We'd like to skip to the end and produce instruments that sound as good or better in 10 years than when new.

https://en.m.wikipedia.org/wiki/Accelerated_aging

It certainly is possible to produce carbon and other trace elements along with VOCs and water, but we endeavour to find a happy medium.

[GeorgeH]

3 hours ago, dan gall said:

We'd like to skip to the end and produce instruments that sound as good or better in 10 years than when new.

A goal that is basically impossible to objectively determine whether or not it has been achieved. 

[Don Noon]

8 hours ago, dan gall said:

the objective is to use accelerated aging techniques to produce wood similar in properties (dimensional stability, sound, etc) to old instruments that we know to sound good.

That was my initial thought in going the route of torrefied wood.  However, after more than a dozen years at this, I find that there are still some characteristics of good old instruments that are not matched with torrefied wood.  Better or worse depends on the player or listener.  But for sure torrefied wood has advantages over fresh wood, unless you like to hit things with your fiddle.

[dan gall]

On 7/25/2023 at 7:03 PM, Don Noon said:

That was my initial thought in going the route of torrefied wood.  However, after more than a dozen years at this, I find that there are still some characteristics of good old instruments that are not matched with torrefied wood.  Better or worse depends on the player or listener.  But for sure torrefied wood has advantages over fresh wood, unless you like to hit things with your fiddle.

I could have been more precise in my wording.  My reading of your and other luthiers’ contributions on this site has convinced me that instruments are complex systems, no matter how much reductive (non-materials) engineers and mathematicians would like to believe otherwise.  Are there simple components that are easily modeled?  Yes.  Standing waves, golden ratio, etc.  I avidly read this forum’s threads about grounds, varnishes, interior washes, etc.  It is obvious to me that conventional finite element modeling software is unfit for purpose, even if one fudges things via parameterization of certain surfaces (and mimicked any skin penetration gradients similarly).

However, even if the only thing I get out of this process is dimensional stability and insect/rot resistance it would be worthwhile.  This process has been proved to provide these properties to the building trades, per Accoya and Thermony among other brands of outdoor decking.

https://www.accoya.com/products/decking/

My daughter’s cello is a marvelous English 18th century piece, and while it still sounds great, it has warped, probably relatively early in its life such that the f holes are distorted and the arching through them is thusly ruined, at least visually.

Edited July 27 by dan gall
Have -> has

[Don Noon]

On 7/24/2023 at 1:28 AM, dan gall said:

I also read of your experiences with toasting wood too thoroughly and postulated that higher pressure at lower temperature might solve some problems. 

Higher pressure is a risk for seals and safety.  Also, with steam at lower temperature and higher pressure, you have liquid water.  The wood starts out with plenty of water to worry about, assuming you're packing the chamber efficiently.

After a lot of testing, I settled on relatively low temperature and pressure, then cook for a relatively long time.  150-160 C, 240 kPa.