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Old purfling stock too brittle to bend


Rob Fowler
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I’m at the stage of adding purfling to a
back of my first violin. I had bought some old stock from a
deceased luthier’s estate. It’s the real wood kind and
not fibre. I’m having a devil of a job to get this stuff to
bend without snapping. I’ve already tried just dry heat on
the moderately hot bending iron and working the purfling very
gradually over the iron. Also tried wrapping a damp thin piece of
cloth round the bending iron strap whilst bending so that some
steam could be generated to assist in bending. Also tried a quick
soak in water which was more-or-less in and out of the water to wet
it and tried another piece with a soak of up to 5 minutes. The
longer soak resulted in the purfling coming to pieces and the
shorter soak dried off to quickly to assist in bending. Everything
I’ve tried so far has failed and I’m now of the opinion
this stuff is just too brittle to do any bending. Do any of you
know of a way to rejuvenate this purfling so that it can be bent? I
was thinking of sealing it in a bag with a couple of potatoes for a
week or so to see if it would take up some of the moisture and
therefore make it more pliable. My most recent thought is to buy
some new stuff so I can now get on with the job but I’ve
still got about 30 strips of this old stock that I don’t
really want to assign to the bucket. Perhaps I could scent them and
use them as joss sticks!

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I got the glycerine and mixed it with water.
It took three coats of the 1:5 solution over two days to make this
purfling pliable enough for bending but in the end it worked great
and it turned a batch of brittle stuff into useable material. I
found this part of fiddle making quite challenging and I’m
sure I’ll make a better job of it next time. Still,
there’ll always be more challenges ahead! Marilyn, I’ve
got about 20 strips of this brittle purfling left and I may try
your fabric conditioner on some of them in the future. Thanks to
all for your help and posts.

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Fulton uses ammonia only to prevent mold growth on the plates which he stores wet to keep them ready for his plate-bending technique, which involves immersion in hot water and forming with wedges, cauls, and clamps.

Bending wood with ammonia requires high pressures and dangerously pure ammonia, I believe. I do not know of a violin maker who does it that way.

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Hi Andres you wrote... "dangerously pure ammonia" - tell me about it!

There was this dairy where the cold rooms weren't getting cold. I was called in. I walked around looking at everything - and noticed two things...

i) the piping wasn't icing up downstream of the direct expansion valves (which is fairly normal) and

ii) there were about 12 empty ammonia cylinders at the back of the workshop.

It was unlikely that all the DX valves had failed simultaneously - so I guessed that the system was almost completely filled with liquid ammonia.

Turns out that the refrigeration type that the dairy was using - his standard answer to lack of cooling was to add more ammonia to the system!!!!

Standing around while the excess ammonia was pumped out of the system and back into those bottles left a smell that I will never forget.

Next step was to strip and replace the valves in the refrigeration compressors. Reed valves don't handle slugs of liquid too well.

So there's no advantage to treating tonewood with ammonia? Acoustically or for colour to simulate great age.

cheers edi

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Glycerin is a pretty good plasticizer for a lot of things, but do you really want to permanently plasticize your purfling, and possibly also the glue and surrounding areas?

What might be the sonic effects of gluing in purfling with rubber cement?

I do something similar to Marilyn, except that I don't use fabric softener.

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These are valid points you raise David and
questions which I can’t answer. Perhaps someone who has
already done this to their purfling for a finished instrument may
care to add a comment or answer your questions. It seems it has
been done in the past by some and so there must exist some
experience on the effects. Or perhaps the effect of adding a little
glycerine is negligible and that’s why the tip is so freely
given. My first thoughts on getting moisture back into the wood was
to somehow put it in a sealed container (sealed polythene bag or
string tube) with a potato or something else that would slowly
release its moisture so that the wood could absorb it. I guess the
quick fix of the glycerine appealed to me and let me get the job
done but I may regret this fix at a later date. I appreciate your
post – thanks.

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Hi Rob Fowler,

I had some experience with brittle purfling and finished up slinging the lot!

If purfling does the job of protecting the edge of the violin, brittle purfling won't be very good. However if you want to use it, wrap it in a damp cloth and leave it for a couple of hours - the purfling should be mor bendable.

Merry Christmas Wolfjk

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"><B">http://en.wikipedia.org/wiki/Fabric_softener

Now that's perfectly clear! Lots of unknown results there to think about--including the use of silicone.

So what EXACTLY do you use, then, David? It seems like you're much more eager to buy the beer than give helpful advice.

Don't some people believe that one factor in the tone of old instruments is flexibility at the edges from the purfling becoming less well glued? If that's the case, flexible purfling may be an advantage, not a problem.

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quote:


Originally posted by:
stradofear

Now that's perfectly clear! Lots of unknown results there to think about--including the use of silicone.

Fixed your Wikipedia link.

quote:


Originally posted by:
stradofear

So what EXACTLY do you use, then, David? It seems like you're much more eager to buy the beer than give helpful advice.

Thought I was clear by saying I do something similar to Marilyn, except not using fabric softener, but maybe I wasn't.

I moisten the purfling with water using a rag a couple of times, wipe off any excess water, and put it in a PVC tube capped at both ends, also containing a wet rag in such a way that it doesn't touch the purfling. I only use special secret water from my tap though, a municipally delivered mixture sourced both from wells and the Huron River. I refuse to give any further details on this water or its composition, but will try to make up for holding out on you by buying you this beer.

quote:


Originally posted by:
stradofear

Don't some people believe that one factor in the tone of old instruments is flexibility at the edges from the purfling becoming less well glued? If that's the case, flexible purfling may be an advantage, not a problem.

Yes, some people believe that. Some people also believe that viscous materials and flexible glues damp sound. If I wanted greater flexibility at the edge, I suppose I'd try to achieve that with arching and graduation, or a deeper purfling groove, rather than using a non chemically bound plasticizer which would almost certainly migrate to other locations over time.

Glycerin is also heavier than water, and attracts moisture.

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