How much oil does a new flute absorb?

Irish Flute
1

You know, I’ve been making these things for about 30 years now and never actually once got round to determining how much oil a new flute absorbs. I’d often thought about it, usually seconds after plunging the hapless victim into the oil bath. But yesterday, I caught myself and remembered to weigh the squirming varmint before plunging. Today, I took it out, wiped it down, let the surface oil soak in and weighed it again - the difference in weight being some kind of indicator of the amount of oil now impregnating the corpus.

To put it in context, the now-thoroughly-drowned test object is a keyless GLP in Cooktown Ironwood. It comprises head, barrel, LH and RH with integral foot. I didn’t include the cap in the measurements. Results so far:

Before oiling: 214.8gms
After oiling: 221.4gms
About 5 hours later: 221.2 gms.

I use linseed oil, thinned about 20% with natural (gum) turpentine. I imagine that the slight reduction after a further 5 hours could be the remnants of the turps evaporating off, but it could equally just be a change in moisture content of the wood with changing atmospheric conditions. They’re the kind of day-to-day variations you can see in the weight of a flute even if it’s not being played.

So we’re looking at around 6.5gms of oil (and turps), about 6.9mL, or a 3% increase in weight. To set 6.9mL in a more familiar context, 5mL is a teaspoonfull.

It will be interesting to see what the second coat I normally give flutes does. Will it absorb any more or am I wasting my time? (I’d give it a second coat anyway as it makes it look nicer!). Should more absorent timbers receive more coats? Or longer dippings? Will this flute continue to absorb oil ad infinitum or will it taper off? Place your bets now, ladies and gentlemen …

Terry

2

Oh boy! A chance to display my ignorance!

Will it absorb any more or am I wasting my time?
Yes, but exponentially less each time.

Should more absorent timbers receive more coats?
Yes

Or longer dippings?
No

Will this flute continue to absorb oil ad infinitum or will it taper off?
Taper off

The above is a SWAG and has nothing to do with any knowledge of the author… (Ah, that means I’m guessing, eh?)

3

Hi Terry,
Too much time on your hands? :smiley:
Cookstown Ironwood seems to be a fairly non-oily wood, kind of reminds me of Red Oak. Now a real test sould be to emerse a wood like Blackwood and see how many micro-grams that will absorb! My guess, Boxwood would probably obsorb the same as Cookstown Ironwood…

Iwould think once the pores are filled with oil, and the oil drys, that the wood shouldn’t take much more oil. Unless there is some evaperation of the oil leaving room for more absorbtion.
Good luck!

4

I’ve always wondered how fast the oil penetrated. if you placed boxwood or other light colored wood into oil and cut the stick in half (not a flute) how far does the oil penetrate a day? Does saturation ever happen, or does the oil stop after a certain point?

PS, Saw one of your piccolos this morning, had to leave befor the guy started playing at the session though. Hopefully he will be playing next week.

5

I swear, the cocobolo Hammy I just sold would give up some oil to the oil bath. And one of my boxwood flutes would lap it all up and ask in its little Oliver Twist voice, “May I have some more?”

6

wouldnt it make sense to also mass the oil that it was bathed in, before and after? i’m sure, however, that this is much easier said than done.

7

Cheeky young whippersnipper! No, never been busier (sigh). Still, can’t begrudge a bit of time to know our materials better. It doesn’t actually take long to measure the weight of a flute!

Cookstown Ironwood seems to be a fairly non-oily wood, kind of reminds me of Red Oak.

I think all our regular woods are non-oily. Indeed I can’t think of many woods that I’d consider oily - Teak perhaps? Lignum Vitae is waxy, and Afrikan Blackwood resinous. But you’d have to squeeze a lot of box or cocuswood trees to get a glassful!

You mean American Red Oak? That’s a lot softer and coarser. The Ironwood doesn’t have the medullary rays you see in oak, more the interlocked grain you see in eucalypts (although it isn’t one).

Now a real test sould be to emerse a wood like Blackwood and see how many micro-grams that will absorb!

Hmmm, not sure that’s any more of a real test than measuring a cooktown ironwood flute! Perhaps you meant a more interesting or generally relevant test?

There’s actually method in my madness. Like you I suspect that there won’t be much oil absorption in a blackwood flute (due to the high level of resin). But it makes better sense to measure something you think will happen before you measure something you think wont happen. Proves the system. I’ll get to the blackwood and boxwood later.

My guess, Boxwood would probably obsorb the same as Cookstown Ironwood…

Seems a reasonable guess, given fairly similar densities, but boxwood is a lot finer, and that might reduce the oil intake. We’ll see …

Iwould think once the pores are filled with oil, and the oil drys, that the wood shouldn’t take much more oil. Unless there is some evaperation of the oil leaving room for more absorbtion.
Good luck!

I wondered if it might soak in a bit, before polymerising, thus leaving some scope for more to follow. But who knows? Even with this new data, we might find it is open to more than one interpretation!

Terry

8

I’ve never managed to get it to soak in far, let alone fast. I think the best we can hope for is a build up of a reasonably water-resistant film at the surface (but not just on the surface).

PS, Saw one of your piccolos this morning, had to leave befor the guy started playing at the session though. Hopefully he will be playing next week.

Heh heh, you’re lucky to get away with your hearing intact!

(Not actually true - they are capable of being played at a reasonable volume.)

Terry

9

Yes, that would be interesting, although it might just tell us how much more I wiped off the flutes after the dipping. Not so easy to do though - my scales achieve 0.1gm resolution by limiting the total weight to 500gms - I would need much fancier scales to achieve that level of resoultion with a couple of kg of oil.

Incidentally, the mass returned to 221.4 gms today, so that 221.2 gms I registered yesterday was probably was just a change in atmospheric humidity. It’s back in the oil now, so tomorrow we should know if it absorbed any more.

Terry

10

This is devilishly penetrative stuff it soaked right through 2 inches of beech on my kitchen surfaces despite being only applied from the top and 6 years later is completely non absorbent.

http://www.flints.co.uk/acatalog/Deks_Olje_Saturation_Oil.html

11

How fast does oil penetrate? Seems pretty slow if you leave the pesky stuff to it’s own devices, and more or less so depending on humidity. We didn’t bother waiting around at vH - oil penetrates (as far as it’s likely to) quite quickly when you force it into the wood under pressure :smiling_imp:

As to how deep it penetrates, it’s like Terry says, not much at all: Even after forcing the oil into the wood under pressure, the penetration appears to be far less than .5mm into boxwood.

Now I know some of you are probably thinking “So how can you tell the pressurization actually works?” Well, if you take the wood immediately out of the oil after pressurization, and then try to wipe the instruments dry, you’ll find the task quite impossible - oil will seep from the pores of the wood nearly as fast as you can wipe it. We had one new guy at the shop who neglected to follow my instructions with regards to how long to wait before removing a dozen instruments from our pressure vat. The poor guy spent several hours trying to get the parts dry, but the wood was still sweating when I finally told him to pack it up and go home for the day (it was quitting time), he could have been there all night, lol!

Loren

12

I’ll admit to performing my own oil adsorption experiments. They have limited applicability to flutes and the appropriately dense woods from which they are made.

I had been messing around with my unpatented “Acoustical Soundwave Amplification Units”, also commonly referred to as tuning corks. I was worried that the wooden cork could absorb moisture then swell and possibly burst the head of the flute. So in efforts to arrest the absorption of moisture, I soaked the dowel rod over night in Refined Linseed Oil. To my surprise I was able to fully saturate a 1-inch section of rod.

*Note – I’ve since abandoned the use wooden dowels for tuning corks. I deemed the incurred risk as unacceptable. So I now use Delrin stoppers.

My experiment was with “hard wood” dowels. These are sold at the hardware store and have an appearance similar to beech, but of are of some tropical origin. To my surprise over night the oil would penetrate up about 2 cm. This was verified by cutting off sections of the dowel until I reached a section that was fully saturated. This deep penetration of oil is primarily due to invoking the capillary action of the wood. This is far different than the radial migration of oil, as applied to the bore and exterior of a flute. In fact the radial absorption of the rods was so little that is was immeasurable to me. Also the density of the “hardwood” dowel is well below that of typical flute woods, so there are more and greater voids between the grains. I also did the test with Almond Oil and found the penetration to be approximately half that of the Linseed Oil. (Theory ->) I believe this is simply do to the more viscous nature of Almond Oil.


Terry, I’m curious why you thinned your Linseed oil with turpentine?


All the Best!

Jordan

13

To increase its mobility. Seems there are a few ways to improve penetration:

  • thin the oil to make it less viscous (what I have been doing).
  • heat the oil to make it less viscous (some makers do this, 45 degrees C, 113F seems to be a popular temperature)
  • put pressure on the oil (as Loren has mentioned)
  • use a vacuum to pull any air out of the wood, then release it and let atmospheric pressure force the oil into the cavities created
  • a combination of the above.

I like the sound of the vacuum approach - it should avoid the problem Loren mentioned of oil oozing back out once the pressure is off - but I imagine that evacuating the space over the oil is going to invite a lot of evaporation, with the oil fumes condensing on the nice cold surfaces on the inside of your vacuum pump! There are probably ways around that. Whether there really is much air to be pulled out from these very dense woods is probably the greater question.

I am interested in trying the heating the oil approach some time. It would be interesting to compare with the results above to see which gives the best penetration.

Jorden’s other experiences certainly make sense. It’s always good to imagine wood as a bundle of straws - plastic drinking straws in the case of african blackwood. Moisture (sap) is designed to be carried by these straws all the way up the tree, so mobility of oil along the grain is good. Getting it to cross the grain is the issue we face.

Now, in today’s news, the weight after a second oiling and drying is 223.7gms - so it gained a further 2.3 gms on the second oiling. The first oiling as you remember it gained 6.6 gms. So a total so far of 8.9gms.

So the law of diminishing returns is certainly at work, as I think we all suspected, but the second coat is certainly warranted. I’ll do a third coat in a few days just to confirm the trend.

Terry

14

Hmm, I suspect there’s very little air that could be removed, and talk about diminishing returns (all the issues you mentioned), still, who knows? If any one is ever going to get around to trying it, I suspect it’ll be you Terry!

Our thought was not try for maximum absorbtion, but rather high polymerization of the oil that did penetrate. To that end, we used additinal drying/hardening agents. We also oiled the wood several times (buffing on the compound wheel between oilings), using at least 3 different modes of application, and in some cases slightly different oil mixtures, for each mode, as required. Tons of work, but well worth the effort.

You “Irish” flute makers should consider yourselves lucky, you don’t have to dye or acid stain your instruments as well, as recorder and Traverso makers often do! (Yes, I know some makers of Irish flutes do stain/dye on occasion, just not as a general course.)

Loren

15

Interesting experiment Terry. I wish I had an accurate scale - it would be interesting to try this with Boxwood, Blackwood and Mopane, as well as with woods of the same kind but of differing dryness. If you try this, let us know.

In my shop flute parts sometimes sit on pins on a surface left oily after oiling. With Mopane and Boxwood I see some wicking of the oil into the grain of the wood. Same with blackwood, but to a lesser degree. When I oil blackwood I do see some absorption. I am using “refined linseed oil” from Daniel Smith’s, a purified raw linseed, right out of the can unheated - although sometimes its a few months old. I avoid the use of thinners, turps especially, and am not that concerned about penetration. Proper oiling in use seems to be a more important factor, as well as protecting the instrument from dryness. So far my instruments have an acceptable survival rate, even iun places like Arizona.

Casey

16

Heh heh, love the quote about the quail, Casey!

Mother Nature seems to be playing little tricks with the experiment - this morning the flute weighs a whole gram more than yesterday (nope - checked the scales - the calibration weight still weighs 100.0 grams). The flute was standing beside an open window and a pleasant cool, moist change went through last evening, so that probably accounts for that. A very clear reminder though that even in a freshly oiled flute, moisture will still move in and out, hopefully moderated, but never stopped.

Anyway, the outside is now perfectly dry, so back into the oil for dunking #3…

Terry

17

Hmmm. Terry, d’you think the oil is being taken up almost entirely through the endgrain, as in SillyDill’s dowel experiment (saturating a 1-inch hardwood dowel overnight…blimey!).

I’m wondering about the ‘real world’ oiling we do once we have the flutes in our possession - the usual ‘swab the bore with an oily rag’ approach rather than total immersion in an oil-bath.

After oiling, I usually leave my flute-parts lying at an angle in a tupperware box, with the ends sitting on a piece of kitchen paper in the bottom of the box. I reasoned it would give the oil a ‘chance to soak in’ and any excess would drain out on the kitchen paper.

Now, thinking about it from all the posts here, what’s likely to happen is that any excess will indeed drain, but could well be sucked up through the tenons’ endgrain by capillary action (unless the kitchen towel has a greater ‘osmotic’ pull on the oil, for want of a better expression).

Which begs the question, do the flute’s dimensions change with oil absorption? ie will my tenons be a tighter/looser fit depending on oiling or not oiling?

18

It’s a fair question, but I think not. When I’ve had reason to turn down a tenon AFTER oiling, I’ve quickly cut through the film of oil at the surface and hit dry wood under. If the oil had soaked significantly up the bundle of straws from the ead, there wouldn’t be dry wood under.

I remember hearing somewhere a rule of thumb that water soaks 10 times faster up the straws than across them. We know the oil only soaks in a fraction of a mm - ten times that is still only a mm or so.

Also if we consider a head, say 170mm long, 19mm ID and 27mm OD, it will have 43 times the side grain access to the end grain access, so that would seem to overwhelm our ten times rule of thumb.

So to summarise, I’d agree that the oil penetration will be greatest at the end grain, but it still won’t be much!

I’m wondering about the ‘real world’ oiling we do once we have the flutes in our possession - the usual ‘swab the bore with an oily rag’ approach rather than total immersion in an oil-bath.

After oiling, I usually leave my flute-parts lying at an angle in a tupperware box, with the ends sitting on a piece of kitchen paper in the bottom of the box. I reasoned it would give the oil a ‘chance to soak in’ and any excess would drain out on the kitchen paper.

Now, thinking about it from all the posts here, what’s likely to happen is that any excess will indeed drain, but could well be sucked up through the tenons’ endgrain by capillary action (unless the kitchen towel has a greater ‘osmotic’ pull on the oil, for want of a better expression).

Which begs the question, do the flute’s dimensions change with oil absorption? ie will my tenons be a tighter/looser fit depending on oiling or not oiling?

Heh heh, another good question, and one that has been on my mind too. I’ll try to remember to measure it before and after dunking the next victim. I’d suspect, given that not much actually soaks in at any one point, we won’t see too much expansion.

Terry

19

OK, the third oiling produced only a 0.3gm increase in weight, negligible when compared to the initial 6.6 gms, and the second oiling’s 2.3 gms. My guess is that the first dose soaks in a bit and sets, forming a barrier, and the second largely fills any remaining space near the surface. The third hasn’t much room to go anywhere. Hopefully the water experiences the same limitations.

So, at least on this timber, and with this mix of oil and gum turpentine, two overnight oilings seems to do about as much as we can hope for in a reasonable time. It would be interesting to leave a flute in there for a few months, but try explaining that to a customer!

So much more we should be doing to understand our materials better - trying the same tests on different woods, with different oils, with different periods, at higher temperatures and under pressure, a few long vs a lot of short dippings, etc, etc. Then testing the resultant flutes for uptake of moisture.

Sigh, always so much to do!

Terry

20

Thanks Terry.

I was pondering whether or not my usual routine of oiling might result in the oil being absorbed by the bottom of the tenon where the excess drains, and thus over time throwing the tenon out of round. I’ll look forward to your next report! :slight_smile: