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PostPosted: Fri Nov 02, 2018 11:06 pm 
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tstermitz wrote:
Regarding Terry's experiment.

I think you would agree that wood absorbs humidity over days or weeks rather than over hours.

Both. Wood is constantly absorbing and losing moisture to the atmosphere, and that means it swells and shrinks as the seasons change. I don't think oiling matters much here, but the presence of metal liners can be an issue if the humidity drops too low for too long.

But in the flute situation we also go to a session and fill it with water over the period of several hours, and that's where I expect to see the most radical change. And that's where a film of oil in theory assists by slowing down the ingress of moisture.

Are we in agreement there?


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PostPosted: Fri Nov 02, 2018 11:07 pm 
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Now those 3 hours have passed and gone, and it reached 52.8gms, a total gain of 0.4gms since starting. A 0.8% increase in weight.

I aired the head for another hour and it went back to 52.7gms. I'll air it overnight and see if it returns to where we started.

There is another theory which suggests that flutes absorb water not so much from that which condenses inside them, but more from the water vapor itself. I might go on to have a play with that theory.

Happy to try out any other suggestions...


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PostPosted: Sat Nov 03, 2018 11:55 am 
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I'd like to know whether an experiment using a tapered bore body section would produce the same results as an unlined head.
The reason I suspect there may be a difference is because I think water enters and leaves wood most easily/quickly via the end
grain.

An unlined head, being cylindrical and with a bore aligned with the grain doesn't really expose much, if any, end grain,
aside from at the socket, which may not even get wet while playing. In contrast, a body section with a conical bore must expose
some end grain on the bore surface itself, because the grain runs parallel and the surface of the bore does not. I expect this to
make some difference in the rate at which moisture is absorbed and lost over the short term (when playing and shortly afterwards,
especially if the flute is not swabbed out).

In long run, with long term changes in humidity during storage, I suspect moisture to find its way in and out via all surfaces regardless
of oiling, and this will almost inevitably cause problems for any section of the flute that has a metal liner. In my experience, it is extremely
rare to find an antique flute that has not cracked if it had a tuning slide, regardless of whether its head was fully or partially lined. Partial
lining sometimes just prevents the crack from reaching all the way to the embouchure. French flutes that have metal lined sockets often
have cracks there too (so much for protecting the socket using a liner!). Older baroque flutes without tuning slides are usually not cracked.
The main point, I think is that wood needs the freedom to move.


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PostPosted: Sat Nov 03, 2018 12:31 pm 
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Terry McGee wrote:
Wood is constantly absorbing and losing moisture to the atmosphere, and that means it swells and shrinks as the seasons change. I don't think oiling matters much here, but the presence of metal liners can be an issue if the humidity drops too low for too long.

But in the flute situation we also go to a session and fill it with water over the period of several hours, and that's where I expect to see the most radical change. And that's where a film of oil in theory assists by slowing down the ingress of moisture.

Are we in agreement there?

How much of an oil film is actually retained to slow down ingress of moisture? That's the big question, I would think.

I imagine most of us who oil our flutes don't do it all that often. At least not as often as we swab out the moisture if we're playing on a regular basis. I can't believe there's much if any oil left on the wood fibers exposed right at the surface of the bore, with constant damp swabbing and the polishing effect of the swabbing material. Even if a hint of oil remains in the cellular structure of the wood just below the surface, there should be much more surface area exposed and basically oil-free after all that constant damp scrubbing of the bore.

Disclaimer, I'm not a flute maker or wood biologist but I've done some woodworking and I'm loosely familiar with moisture effects on wood. I'm just a little skeptical that much oil is retained in a flute bore that's being scrubbed daily with a damp cloth. Not unless it's being oiled more often than most of probably oil our flutes.

Maybe the primary benefit of oiling is slowing down moisture transfer at the exposed end-grain of the embouchure, tone holes, and tenons? Oil isn't physically removed by regular swabbing in those areas. They'll get damp, but the surface oil isn't going anywhere.


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PostPosted: Sat Nov 03, 2018 12:59 pm 
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Recommended reading on this subject:
https://www.dolmetsch.com/woodoilwater.htm

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PostPosted: Sat Nov 03, 2018 4:29 pm 
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It's now next morning in the antipodes, and the head has been airing for about 18 hours. Now weighs in at 52.6gms.

So to summarise so far:

Started at 52.4gms, freshly turned from the day before.
After an hour of being wet inside and then mopping out, it reached 52.6
This dropped to 52.5 after airing for an hour.
Another 3 hour internal wetting and mopping out saw it rise to 52.8
Which dropped to 52.7 after an hour of airing,
And dropped further to 52.6 after a good night's sleep.
Net gain after 24 hours about 0.2gms.

So clearly, untreated blackwood does absorb and subsequently lose moisture, although not much. Consider though this possibility. You take your brand new untreated blackwood flute to the Boxwood flute festival, or the Catskills or some similar intensive event. You sit in class all day learning tunes, and then play well into the night, every night for a week. Hopefully remembering to mop out thoroughly before breaks and before tumbling exhausted into bed.

We see that it's taking more than a day to lose the moisture acquired in 4 hours simulated playing. So in a week of heavy playing the flute would probably absorb considerably more. The question becomes can that newly acquired moisture permeate through the timber in that timescale? If it can, the outside will be expanding too and the buildup of dangerous forces avoided. If it can't, the inside swells, the outside doesn't, and finally something has to give. If the timber has a weak spot, this force will find it.

I think maybe the next step in our experiment is to let the head air some more, to give us an idea of how long it takes to return to original moisture levels. Take the rest of the day off!


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PostPosted: Sat Nov 03, 2018 7:03 pm 
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All very useful and interesting so far. A thank you to our learned friends.

I went ahead and lightly oiled the bore of the Murray with Alisyn bore oil. A synthetic, it seems quite nice, whatever it is made from. The other part of my original post was to ask what oils people recommended for Blackwood. I have read dozens of articles, with the usual caveats about boiled linseed oil and so on. McNeela provides grapeseed oil in their flute maintenance kit. Grapeseed oil is used as the base in many cosmetics and you can buy litre bottles of if for next to nothing here. Any experience with that?

I'm not allergenic to nuts myself, so interested to hear about almond oil and similar also.


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PostPosted: Sun Nov 04, 2018 1:23 am 
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Sam Murray recommended linseed oil, a bit to my surprise. But only very occasionally and when it was really needed. Other makers always recommended almond oil to me.

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PostPosted: Sun Nov 04, 2018 6:27 am 
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Terry McGee wrote:
I think maybe the next step in our experiment is to let the head air some more, to give us an idea of how long it takes to return to original moisture levels. Take the rest of the day off!
A future step might be to wet a piece of scrap that would fit into a micrometer and see how the dimensions change. Or have you already done that experiment for tenon design? I guess it would be too small to detect a difference in weight.


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PostPosted: Sun Nov 04, 2018 6:34 am 
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Mr.Gumby wrote:
Sam Murray recommended linseed oil, a bit to my surprise. But only very occasionally and when it was really needed. Other makers always recommended almond oil to me.


Be very careful with linseed oil, avoid the blow hole, for linseed oil accumulates and will change the geometry of the hole. I use linseed oil rarely on the outside of the flute with all keys removed and in very small quantity, as opposed to the metric tons of almond oil....


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PostPosted: Sun Nov 04, 2018 7:10 pm 
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You'll remember from the summary above that the head under test ....

"dropped further to 52.6gms after a good night's sleep."

That was yesterday morning. I measured it again late in the day at 52.5gms. Aha, I thought confidently to myself, it will be back to 52.4 (the starting weight) by tomorrow morning.

But Robert Burns, not specifically noted for his flute playing, reminds us that....

“The best laid schemes o' mice an' men
Gang aft a-gley.”

(From “To a Mouse”.)

What in fact has gone "a-gley" is the humidity, which I'd reckon is about 90% outside at the moment. It's very quiet and still out there, and there have been a few drops of rain, so the moisture is right on the brink of condensing out and dropping out of the sky. Workshop (which I tend to leave open to atmosphere in the gentle months) is sitting at 80%.

All of this leading up to the revelation that the airing flute has now regained some weight, and is back at 52.7 gms!

Now that's actually quite interesting ("Always look on the bright side of life....), as it sets our experiment in some context. The moisture absorbed from 4 hours of simulated playing is about the same amount of moisture that can be absorbed overnight from a sudden burst of high humidity.

With rain expected later today and for the next day or two, I'd imagine the weight of the head will continue to rise. But let's see....


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PostPosted: Mon Nov 05, 2018 2:37 am 
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Apologies, Paddler, for taking so long to respond to these points....

paddler wrote:
I'd like to know whether an experiment using a tapered bore body section would produce the same results as an unlined head. The reason I suspect there may be a difference is because I think water enters and leaves wood most easily/quickly via the end grain.

It's a legitimate question, and one I feel we should investigate. I might let the current experiment run its course first, as I've found you often get surprised by the twists and turns along the way. I'm thinking that a keyless LH section might be a good test subject. It has lots of surface area compared to its weight, and a good steep taper, presenting a good amount of "oblique grain".
Quote:
In long run, with long term changes in humidity during storage, I suspect moisture to find its way in and out via all surfaces regardless of oiling, and this will almost inevitably cause problems for any section of the flute that has a metal liner. In my experience, it is extremely rare to find an antique flute that has not cracked if it had a tuning slide, regardless of whether its head was fully or partially lined. Partial
lining sometimes just prevents the crack from reaching all the way to the embouchure. French flutes that have metal lined sockets often have cracks there too (so much for protecting the socket using a liner!). Older baroque flutes without tuning slides are usually not cracked. The main point, I think is that wood needs the freedom to move.

Yep, echoing my experience.

One of the light-bulb moments for me was when I noticed how often the 19th century mahogany cases containing flutes with cracked heads and barrels had also cracked. For the same basic reason - in both flute and case, the natural movement of the wood with humidity was constrained. In the case of the flute, by the metal slide firmly lodged inside. In the case of the case (ooh, ugly wording!) by the fact that the top and bottom panels were glued to a frame. That presents no problem along the front and back, because the grain of the frame sections are running the same way as the grain in the panels. But at the ends, the frame runs across the grain of the panels, neatly stopping them moving. And they didn't like that.

So, I tackled both problems. My flutes have partial slides buffered with cork to allow the timber to move. And my cases have floating panel construction, to allow the panels to move. Better to accommodate Mother Nature than fight her. Sigh, if only our political masters could get that message....


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PostPosted: Mon Nov 05, 2018 4:17 am 
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dcopley wrote:
Recommended reading on this subject:
https://www.dolmetsch.com/woodoilwater.htm


Heh heh, it's a big read, isn't it. Right at the very end is a link to Dr Brian Blood's recommendations on care of Dolmetsch Recorders. (Brian is a son-in-law of the late Carl Dolmetsch, and is now managing director of the firm. I never met Carl, but caught a glimpse of him when visiting the factory at Haslemere in 1974. The staff seemed very much in awe of him.)

In the care notes, Brian mentions:
Dense hardwoods like grenadilla [posh term for African Blackwood] generally require very little additional oil, but porous woods like boxwood and even softer fruit-woods like cherry or pear as well as the ubiquitous maple, if not already treated in some other way (see below for further comments on this), will benefit from a regular treatment of the inside of the acoustic bore with a good well-drying oil.

And later:
Lighter oils (mineral or walnut) are to be strongly recommended because they dry more quickly.

Now, clearly, mineral oils do not dry. But perhaps he means they soak in more quickly?

But then he goes on to say (near the end):

"Bore oil" that you buy at the local music store in little bottles is an entirely different
story. It's often mineral oil or petroleum oil and has a number of interesting
characteristics. First, it's biologically incompatible (except for special bacteria genetically
engineered to clean up oil spills) so it does not go rancid. Second, it dries much slower,
and is much more immune to natural and man-made detergents, so it stays in the bore
much longer. Third, it's a very effective vapour barrier. But it's not as compatible with
wood as the nut oils, and it's difficult to clean out of the bore (keeps building up in waxy
layers). Personally, I avoid it. Clarinet and oboe players swear by this kind of oil, but
then again, these are the same people who take Grenadilla (African Blackwood) which is
absolutely beautiful with long streaks of browns, reds, and blacks, and stain it jet black
(and lacquer the outside of the instrument) so it looks like plastic.

So, perhaps a little oddly, he at first seems to promote mineral oils because they don't go rancid, stays in the bore longer and forms a "very effective vapour barrier". But he seems confused on whether they dry or not. Hmmm.

Interestingly, the preceding article seems to be reasonably positive about mineral oils. Most of the modern commercial instrument making companies promote or sell mineral oil. I know it doesn't fit easily with our preconceptions....


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PostPosted: Mon Nov 05, 2018 6:10 am 
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Hi Terry, I went with a very light touch of Alisyn bore oil, inside and out.

The Dolmetsch article actually mentions it:

"For the connoisseur, Aerospace Lubricants, Inc. makes a series of lubricants of differing viscosities. NMR and infra-red analysis indicates that these are linear hydrocarbons. They are extremely pure, narrow molecular weight spread materials. This is of importance under high rates of shear, where traditional lubricants may exhibit thixotropic behavior and show a marked decrease in viscosity. They range (low to high viscosity) from Alisyn Valve and Slide Key, to Finger Board, and Bore Oil."

It's very fine, colourless, odourless, and has a very nice feel, more like an organic (I know it's not). A$10 for a small bottle enough for years and years.

So, my present understanding for the Murray Blackwood is, a very light oiling very occasionally is fine. A light non goopy oil seems best. This goes against the McNeela recommendation of no oiling, but I feel here in Australian dry hot conditions I really do think it needs it.

Still interested to hear peoples' experience with grapeseed oil.


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PostPosted: Mon Nov 05, 2018 6:16 am 
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I notice on the Aerospace Industries website that Alisyn Bore Oil is available in various size containers. You can get a 55 gallon drum for US$9.432.50. Enough to oil every Blackwood flute that will ever be made for the next ten thousand years or so. Maybe I should buy a drum and corner the market.


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