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Mark Norfleet

Crack reinforcement method question.

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Recently a customer brought an older instrument to me that they are considering buying for my opinion on it’s health etc. The instrument is in generally good condition with 4 or 5 cracks in the top that seem to have been recently repaired.  Those cracks appear to have been repaired well and are stable.  The thing I’m unsure about however is how they were reinforced on the inside.  I, like most, use a series of small light cleats (glued to the inside) along most cracks with the grain perpendicular to that of the top (or back).  I’ve seen parchment used to reinforce cracks on a few instruments and was not impressed with the apparent stability of the arching or the effectiveness of reinforcing the cracks themselves and wound up re-gluing at least some of the cracks and replacing all of the reinforcement on those few instruments.  On this instrument, nearly all of the crack reinforcement has been done with what looks like very fine silk fabric.  Fine enough that I can easily see the wood grain through it.  My question is, does anyone here have experience with the long term effectiveness of that method of crack reinforcement?  Questions of sound aside, I do wonder how long the joints will stay glued.  Any thoughts and insights are welcomed, but I’m especially interested in those from folks who have had long term observations and experience with this method.

Thanks Much!

Mark

 

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Like you, I put cleats in when I’m gluing cracks on the top or back. I could imagine an argument for fiber or parchment in areas with multiple cracks close together or at bad angles. I don’t think it’s wrong to use those methods as long as the glue is strong and the reinforcements are well-applied.

As far as observation of longevity of parchment repairs, I can say that I’ve worked on a lot of Hill workshop violins from the late 19th and early 20th centuries, and I found that they often did repairs with thin strips of parchment cut to length, both for cracks and for repaired center seams. Almost all of them are still sound. 

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Depends all on how wide the strips are. If they are not wider than the thickness of the top, there should be no problem. I don't really think that cleats are superior to silk strips or woven polyester, especially if the cleats are thick and there are multiple cracks.

I can see a problem if there is a wide strip of parchment, those sometimes come loose.

Also, a lot depends on how good and strong the glue is that was used to glue the cracks. I have seen repairs that were probably 100 years old,  still pretty much invisible and sound. 

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Thank you both for your responses.  I am however surprised there have not been more!

I should add that I often use linen in areas where there are multiple cracks that are close together, usually on tops right next to the upper and or lower blocks.

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18 minutes ago, Mark Norfleet said:

Thank you both for your responses.  I am however surprised there have not been more!

I should add that I often use linen in areas where there are multiple cracks that are close together, usually on tops right next to the upper and or lower blocks.

Interior linen might be a good reinforcement strategy,  to reinforce areas which might take punches from the outside. Does't  work quite as well for other stresses.

For anyone who doesn't already know, Norfleet is among the best in our business,

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1 hour ago, Mark Norfleet said:

Thank you both for your responses.  I am however surprised there have not been more!

 

Linen used on the top and back for reinforcement is often a hot button issue - zealots on both sides of the argument usually come out in force.  Maybe they're too tired to go another round? I believe that there are past discussions on it here.

 In my experience, I've removed way more than i've installed (removed=lots, installed=0).  I've removed it because it's been rather wide and caused localized buckling along the split.   Perhaps as Christian says: "If they are not wider than the thickness of the top, there should be no problem."  All of the stuff that i've removed has been considerably wider than the thickness of the top.  I've also seen my fair share of stable linen/parchment/silk reinforcements that was quite old.  For me, I know I can install cleats that work, and I won't have to keep thinking about them after I install them.  So, I stick with cleats for table and back repairs, and keep linen for ribs.  

41 minutes ago, David Burgess said:

Interior linen might be a good reinforcement strategy,  to reinforce areas which might take punches from the outside. Does't  work quite as well for other stresses.

For anyone who doesn't already know, Norfleet is among the best in our business,

He also lives in Ann Arbor, right?  You really can't swing a cat around your head with out hitting someone in the trade there..

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46 minutes ago, Jerry Lynn said:

He also lives in Ann Arbor, right?  You really can't swing a cat around your head with out hitting someone in the trade there..

Pretty much. Might be due to toxins in the Huron River. ;)

My cat still likes me, but she drinks the same water. :lol:

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I would have the usual concerns that the silk would create pretty effective hinges, but would not add the kind of stability a cleat would.

We do have a rock star cellist that we re-enforce the inside of his cellos with a layer of silk on the upper ribs and upper back.  It works exceptionally well in that context.

Zealots?

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I like cleats for the stiffness, but have been wondering lately about fabric impregnated with urushi lacquer (might need a cast as a pressure mold for that) as it's hard as nails once it's cured and lasts for at least hundreds of years.  :)

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9 minutes ago, Jerry Pasewicz said:

Zealots?

I've developed a flair for the dramatic I guess.   I blame Rozie and Jacoby. :D

Your hinge theory is right on. The main job of a cleat is to keep the plate from flexing in a localized area. I seem to recall something from the pro narrow parchment crowd that it's providing a barrier to humidity swings for the crack on the inside, like retouching does for the outside???

 

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42 minutes ago, Violadamore said:

I like cleats for the stiffness, but have been wondering lately about fabric impregnated with urushi lacquer (might need a cast as a pressure mold for that) as it's hard as nails once it's cured and lasts for at least hundreds of years.  :)

Hi VdA - interesting material - urushi lacquer - thanks for posting. Questions, questions...

Must one have one own personal tree as a ready-use source?

How long does it keep on the shelf?

How thin is it - would it wick into a crack?

After curing/polymerising is it waterproof?

What is its maximum temperature limit?

May thanks - cheers edi

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44 minutes ago, Jerry Lynn said:

I've developed a flair for the dramatic I guess.   I blame Rozie and Jacoby. :D

Your hinge theory is right on. The main job of a cleat is to keep the plate from flexing in a localized area. I seem to recall something from the pro narrow parchment crowd that it's providing a barrier to humidity swings for the crack on the inside, like retouching does for the outside???

 

Yeah, I blame Jacoby for a lot of stuff too..B)

That is a really tough sell for those pro-parchment crowd.  Parchment is hygroscopic as you know, so not only would it not protect the crack from humidity, the parchment would hold on to the moisture considerably longer than air...essentially making the crack exposed to high humidity for considerably longer.

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1 hour ago, Violadamore said:

I like cleats for the stiffness, but have been wondering lately about fabric impregnated with urushi lacquer (might need a cast as a pressure mold for that) as it's hard as nails once it's cured and lasts for at least hundreds of years.  :)

Urushi lacquer (think tx drawl)?  That's nothin'!  Ah love her!

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2 minutes ago, Julian Cossmann Cooke said:

Urushi lacquer (think tx drawl)?  That's nothin'!  Ah love her!

How many Lone Stars yawl had tonight?  :lol:

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Just now, Violadamore said:

How many Lone Stars yawl had tonight?  :lol:

My cocktail of choice is a good rah.  You know...rah.  Rah!  Rah! Rah!  Rahms with mah.  As in "Mah favrit rah is Dayed's Hayet -- that there's from Pennsylvania."

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28 minutes ago, Jerry Pasewicz said:

That is a really tough sell for those pro-parchment crowd.  Parchment is hygroscopic as you know, so not only would it not protect the crack from humidity, the parchment would hold on to the moisture considerably longer than air...essentially making the crack exposed to high humidity for considerably longer.

Agreed!  

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17 minutes ago, Julian Cossmann Cooke said:

My cocktail of choice is a good rah.  You know...rah.  Rah!  Rah! Rah!  Rahms with mah.  As in "Mah favrit rah is Dayed's Hayet -- that there's from Pennsylvania."

  Did you "red up" your workshop today?  

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4 hours ago, edi malinaric said:

Hi VdA - interesting material - urushi lacquer - thanks for posting. Questions, questions...

Must one have one own personal tree as a ready-use source?

How long does it keep on the shelf?

How thin is it - would it wick into a crack?

After curing/polymerising is it waterproof?

What is its maximum temperature limit?

May thanks - cheers edi

1.  It's commercially produced in Japan.  Lacquer based on a related substance, cardanol (from Cashew Nut Shell Liquid, a by-product of the cashew nut trade) may be substituted and has similar properties and cautions.

2. Long time as in indeterminate, when protected from oxygen.

3. Syrupy, and probably.  You can thin it with turpentine.  It's commonly sold in tubes like artist paints.

4.  Yes.

5.  Similar to phenol-formaldehyde thermosetting plastics.  Scalding water is no problem.

Note for those unfamiliar with urushi, we're talking about the active toxic agent in poison ivy and the other cute little shrubs in genus Toxicodendron.  While the cured lacquer is inert, the uncured lacquer is a dangerously toxic irritant to most people, and must be handled with great care.  There can be a danger from fumes, so a respirator or gas mask may be a good idea.  Personally, I don't react to poison ivy, but have friends who can't get near the stuff.  Until you know how it might affect you, don't take chances. :)

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5 hours ago, Violadamore said:

1.  It's commercially produced in Japan.  Lacquer based on a related substance, cardanol (from Cashew Nut Shell Liquid, a by-product of the cashew nut trade) may be substituted and has similar properties and cautions.

2. Long time as in indeterminate, when protected from oxygen.

3. Syrupy, and probably.  You can thin it with turpentine.  It's commonly sold in tubes like artist paints.

4.  Yes.

5.  Similar to phenol-formaldehyde thermosetting plastics.  Scalding water is no problem.

Note for those unfamiliar with urushi, we're talking about the active toxic agent in poison ivy and the other cute little shrubs in genus Toxicodendron.  While the cured lacquer is inert, the uncured lacquer is a dangerously toxic irritant to most people, and must be handled with great care.  There can be a danger from fumes, so a respirator or gas mask may be a good idea.  Personally, I don't react to poison ivy, but have friends who can't get near the stuff.  Until you know how it might affect you, don't take chances. :)

Hi VdA - many thanks.

In your 2. - possibe reaction with a hydroxyl (OH) rather than oxygen?

cheers edi

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13 hours ago, Violadamore said:

I like cleats for the stiffness, but have been wondering lately about fabric impregnated with urushi lacquer (might need a cast as a pressure mold for that) as it's hard as nails once it's cured and lasts for at least hundreds of years.  :)

Reversability? Is there a solvent which will at least soften the dried coating?

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13 hours ago, Jerry Pasewicz said:

I would have the usual concerns that the silk would create pretty effective hinges, but would not add the kind of stability a cleat would.

We do have a rock star cellist that we re-enforce the inside of his cellos with a layer of silk on the upper ribs and upper back.  It works exceptionally well in that context.

Zealots?

Why does it need the reinforcement?

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11 minutes ago, nathan slobodkin said:

Why does it need the reinforcement?

He plays standing up and in outdoor venues. The instruments get a bit more stress to the backs and upper ribs as a result.664484C8-D714-44DD-A588-FE0B15E427CB.thumb.jpeg.30509af2d1aeb56f7e51ea17181ee57b.jpeg

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On 6/6/2019 at 7:41 PM, Mark Norfleet said:

Recently a customer brought an older instrument to me that they are considering buying for my opinion on it’s health etc. The instrument is in generally good condition with 4 or 5 cracks in the top that seem to have been recently repaired.  Those cracks appear to have been repaired well and are stable.  The thing I’m unsure about however is how they were reinforced on the inside.  I, like most, use a series of small light cleats (glued to the inside) along most cracks with the grain perpendicular to that of the top (or back).  I’ve seen parchment used to reinforce cracks on a few instruments and was not impressed with the apparent stability of the arching or the effectiveness of reinforcing the cracks themselves and wound up re-gluing at least some of the cracks and replacing all of the reinforcement on those few instruments.  On this instrument, nearly all of the crack reinforcement has been done with what looks like very fine silk fabric.  Fine enough that I can easily see the wood grain through it.  My question is, does anyone here have experience with the long term effectiveness of that method of crack reinforcement?  Questions of sound aside, I do wonder how long the joints will stay glued.  Any thoughts and insights are welcomed, but I’m especially interested in those from folks who have had long term observations and experience with this method.

Thanks Much!

Mark

 

Hi Mark;

Sorry... would have responded sooner but I've been occupied with another "situation" for several days.

I've seen some (what appear to be) old repairs fine cloth reinforcement that has held up well, but I personally don't have enough confidence to use this method on the plates (though I'll use a linen on ribs).  I've seen many problems with parchment.  

I've "played" (experimented) with washi paper, though not on customer instruments, as well.  I have no idea how that would hold up long term, though the multi-directional fibers are interesting.

I prefer cleats also, as I believe the reinforcement stabilizes the crack in a different (beneficial) manner (controls flex at the crack) than cloth would tend to do... but I can imagine there are applications, depending on the location of the damage, that a cloth reinforcement might actually be superior.

My 2 cents.

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