Cow hide banjo skin scrap used for top reinforcement

[Paul Breen]

I saw an excerpt in one of Henry Strobel's books on violin repair, where he was talking about cleating cracks. He discusses the importance of light weight, minimal cleats, if they are to be used. He mentions the use of parchment for this but without any further elaboration.

I've got a Roy Smeck "Vita Uke" on the bench that I am bringing back to playable condition. One of the problems to be dealt with are all the top cracks that developed around (and I'm sure as a result of) the seal shaped sound holes. I was pondering how to reinforce this area to both cleat the existing cracks and stabilize the top in this area to stop any more from developing. I started cutting out a thin sheet of Spruce that I was going to use to laminate, with sound hole cut outs, over that entire area. It started becoming a chore to make this and I remembered the excerpt from Strobel's book. So I though I would experiment and try something I have not done before. I cut out a piece from a split hide banjo head that I had saved and easily shaped it with an Exacto knife. I soaked it in water until it became quite pliable, blotted it dry and then used hot hide glue to glue it in place. There was no clamping, I sat with it for the 10 minutes or so that it took to gel and start bonding, stroking it with the glue brush the whole time till it stuck.

This all seemed to work very well and seems to be a good repair solution for the problem. However, I have not done this before and have no track record to re-assure me that this will be a lasting solution.

Has anyone else tried this?

[Hesh Breakstone]

Interesting thread/post Paul and great pics of a very cool instrument too.

Don't know about the suitability of hide banjo heads as cleats but what I wanted to add here is something that I learned in my Lutherie journey.  It has to do with why folks did what they did, used what they used, etc. for the procedures/operations that they had to do.  Not only am I speaking of entire f*ctories such as Gibson back in the day on Parson's street here in Michigan but individual builders, repair folks etc.

What I learned about materials usage back in the day is that they often used what they used simply because it's what they had.  Not the scientific or romantic answer that I had likely wanted to hear but nonetheless I still found it interesting to learn and know.

It's likely that anything that can handle the mechanics of the job was a candidate for consideration and use.  But this does not address the idea of what would be optimum for the task at hand.  

I've seen old popsicle sticks, pieces of a pizza box...., and tons of epoxy-like gunk likely poured into instruments...  At the end of the day though if low mass, low dampening, and high stregnth to weight are the ticket for an optimal material good ole spruce is pretty hard to beat provided that the joint is decent, the grain orientation is correct, the edges are beveled to avoid stress risers, and the glue of choice has been used as it should.

It might be interesting still, even though the cleats are now in place, to repeat your exact steps with a test piece and then keep an eye on it over time.  Hides are typically tough, more massive than spruce, and somewhat flexible as well.  Leather is also used to mute strings on a number of instruments because it has rather high dampening properties.  Not saying it is a bad idea but it would be interesting to see how the joint holds over the seasons in so much as the spruce is going to move as spruce always does with seasonal changes, RH, etc.

Anyway this notion of using what we have available to us fascinates me and I always admire folks willing to try new things.  Let us know how she does over time?

[Eric Steven Johansen]

I've restored several very old parlor guitars using the parchment paper and hide glue method to reinforce side cracks where the were way too numerous and in a group that made standard spruce cleats unworkable. They worked extremely well and  according to the customers they are still quite solid. Not sure about the calfskin idea for some of the same reasons cited by Hesh but please let us know the final results.

[Paul Verticchio]

Eric & Hesh addressed the "mass" issues. The only concern I would have is if the spruce & skin expanded/contracted at extremely dissimilar rates, which could cause cracking. I have no idea how to predict that other than take a wait & see approach.

Nice work, Paul. Best of luck :)

[Paul Breen]

Hesh,

Thanks for your thoughts...a few things.

The term "cow hide" is somewhat misleading, the process for making banjo heads from cow flesh is different from how leather is made. It is not tanned to make leather but rather processed into parchment or vellum.

This is from Wikipedia -

"Parchment is a thin material made from hide; often calfskin, sheepskin or goatskin, and often split. Its most common use was as a material for writing on, for documents, notes, or the pages of a book, codex or manuscript. It is distinct from leather in that parchment is limed but not tanned; therefore, it is very reactive to changes in relative humidity and is not waterproof. Parchment is scraped and dried under tension unlike leather.

Parchment and vellum

The term parchment is now often used interchangeably with vellum, although properly speaking there is a distinction. Vellum (from the Old French velin or vellin, and ultimately from the Latin vitulus, meaning a calf) refers exclusively to calfskin; whereas parchment may be made from a variety of skins, including sheep and goat.[1][2] More generally vellum has been used for finer luxury grades of material, and parchment for coarser sorts. It is only in relatively modern times that confusion between the terms has arisen: traditionally the distinction was more strictly observed, for example by lexicographer Samuel Johnson in 1755, and by master calligrapher Edward Johnston in 1906.[3] However, when old books and documents are encountered it may be difficult, without scientific analysis, to determine the precise animal origin of a skin; and for this reason many conservators, librarians and archivists prefer to use either the broader term "parchment", or the neutral term "animal membrane".
In the Middle Ages, calfskin and split sheepskin were the most common materials for making parchment in England and France, while goatskin was more common in Italy. Other skins such as those from large animals such as horse and smaller animals such as squirrel and rabbit were also used."

The bit of left over banjo head I used is neither thick, heavy or leathery, it is .010" thick, rather stiff and bonded quite readily with hot hide glue to the spruce top. You can't tell from my pictures but there is some curvature across the top and curling along the edges of the sound holes. I started out to make a Spruce overlay to cover the same area that you see in the pictures with the skin patch but ultimately felt like there was little chance of applying a thin Spruce overly of this configuration without it splitting somewhere along the process. The skin (parchment, vellum)  idea was not inspired by found objects I have lying about but rather from what I read in Strobel's book and what I considered to be a viable and reversible solution to the process of successfully applying an overlay that was minimal and strong. Yes, the question of being enduring remains but I have placed my bet and think it's a good one.

Eric,

Do you know if the parchment you have been using is derived animal skin or is it plant fiber?

Here is a few more pictures to share...

Before

All cracks about the sound holes where first glued up with hot hide glue before adding the overlay. There where many and it took a few days and several glue-ups to get them all.

Here is a shot of the interior. You can see that by far the majority of the vibrating area is below the spindly original brace under the sound holes...I did consider damping.

The bridge plate/ brace is also original to the piece. The holes in it are screw holes from Helpful Henry's of Christmas past.

Paul,

Thanks for chiming in. Yes, time will be the decider but I think that may be sorted out sooner than later. We get pretty good temp and humidity swings here in central Illinois.

Tim,

Yes, this was a rather evil experiment, boo-wah-ah-hah!

It's almost done, the bridge has had it's screws removed, holes filled and glued in place. The back has been put back on and I am just waiting for my fret order to arrive to finish things up. Should have her playing again sometime this week.

[Hesh Breakstone]

Hi Paul:

Actually what I had on my mind when I posted previously in respect to using what one has was the reference to Strobel's book and the mention of parchment.  Not sure where the parchment idea originated and it would not surprise me if it was something that Henry may have observed but not originated.  Not elaborating on the material may imply minimal personal experience and hence nothing to add.  But who knows.

What I do know though is that countless times folks engaging in Lutherie arrive at a personal discovery only to find out later that there is very little that is really new....  It's all been done before it seems with a few exceptions.

One of the problems with being a Luthier and endlessly toiling in solitude with chisel in hand is that we tend to not get out much....  With the advent of the Internet and fora it's been a huge benefit at least to me to see and read about what others do for better or worse.

I wasn't being critical of you and think that your work looks excellent.  Hope you don't mind me saying so either.

Where I do have some disagreement with you though and in a gentlemanly way is the use of parchment.

Your Wiki quote says "it is very reactive to changes in relative humidity and is not waterproof."  Seems to be saying it's RH unstable which is where I wondered why one would use parchment over spruce, seasoned spruce.  I understand the difficulty of the radiused surface and how difficult it would be to patch with stiff spruce.  But parchment has no structural rigidity at all, no grain to manipulate, etc.  It's thin, a good thing, not waterproof which also helps it absorb HHG, also a good thing, but the lack of any rigidity and the instability to RH swings seems to make it a completely different sort of material than the traditional spruce cleat.

In my guitar world I'm a fan of side tapes, often linen or some other fabric, flexible, wetted in HHG and installed across the grain on the sides of a guitar box.  Side tapes are often misinterpreted as structural supports for the sides when in fact they suck at this.  What they do well though as evidenced by the countless guitars from many makers who have used sides tapes is potentially help arrest a side crack from traveling further than up to the next tape.  They don't always work at this either.  The material, fabric, linen, cotton, even poly/cotton blends these days becomes stable when it's weave is saturated with HHG if done correctly.  Maybe parchment will have it's instability improved with the application of HHG.  But if not we now have a laminated, two-part composite of spruce and parchment that one of the materials is known to be RH unstable.  Kind of like a bimetallic strip with two dissimilar materials reacting differently to environmental stresses.

I know that you are now vested in this solution and again my hope is that it works very well for you.  My only dog in this hunt is that I wanted to discuss the suitability of parchment for cleats in so much as this is what we do here, discuss things.  Sorry if my post came off as offensive in any way.  That's not my nature, intent, or right to do.

[Frank Ford]

I believe that hide glued and appropriate side tapes can, in fact, help prevent cracks by stiffening the side.  As the side is pressed in, the solid, glued linen tape will avoid stretching, helping to keep the side from cracking as it bows inward.  Same thing for larger parchment or linen patches.  

[Paul Verticchio]

Paul,

I forgot that you live in Champ/Urbana. You're talking about the weather like we have right now. On Thursday, in Jacksonville, it was 96 with 85% humidity. Last night, it dropped to 46 degrees. Today = GORGEOUS!!!

Have a good one, man :)

[Eric Steven Johansen]

Paul, The parchment I use came out of some very old manuscripts I collected as a kid, so I would have to assume they are made of some sort of skin, but I can't say for sure. The information you posted is news to me as I never even thought about what parchment was made of. I can say from my experience that once it's soaked with hide glue and dried it's extremely rigid and stable, at least in my environment here in SoCal.

[Greg Mirken]

Paul, a trick I learned from Paul Hostetter is to use Tyvek for crack reinforcements. A typical use would be to stop cracks from developing at f-holes. It's unbelievably strong, thin, and adds practically no mass. And it's free, because you always get stuff mailed in those Tyvek postal envelopes.

I was worried at first that it wouldn't glue well, being so slick, but it seems to stick exceedingly well with hide glue.

[Peter Poyser]

Quote: "One of the problems with being a Luthier and endlessly toiling in solitude with chisel in hand is that we tend to not get out much....  With the advent of the Internet and fora it's been a huge benefit at least to me to see and read about what others do for better or worse."

 

 

For sure, Frank Ford is a Hero!

 

Quote: "I never even thought about what parchment was made of."

 

People today appear to utilise the phrase quite liberally.

Using it interchangeably to refer to certain thick papers, derived from wood pulp or in many cases, rag.

But vegetable pulp has also been used over the years. Parchment can mean anything really today it would seem, so all the above including all sorts of different animal skins.

Vellum is also often referred to in a completely similar way, but really stems from a French word, and actually means a calf skins in particular. But Vellum gets thrown in the verbal melting pot quite regularly nowadays too.

A lot of differences appear through the ages, but many of these highly visible colour and tactile differences, in reality amount to specific treatments given to enhance the material in various ways; making it appear to be distinctive and especially desirable to a particular group of users for a specific purpose.

I have a pal who has spent his whole life donning a pair of white gloves every morning in the World Famous Bodleian Library, to read Rare and Precious Historic Documents. He then has a good lunch, following which he gives a lecture for a couple of hours to which people will attend from all over the world, as he is one of the Greatest Authorities on Documents of this Type.

http://www.bodleian.ox.ac.uk/whats-on/upcoming-events/2013/sep/tolk...

 

Nice work if you can get it!

My late eldest brother worked for a Publisher nearby who co-owned The Pyrgamon Press.

So named after the ancient Greek city of Pergamum  (Bergama, Turkey), which is where parchment is understood to have been invented in the 2nd Century B.C. So quite a while ago really, leaving lots of room for experimentation and development, over such a long time period.

 

 

Violin cracks fixed with parchment is a traditional fix.

Due to its minimal effect on inhibiting vibration, best allowing the transmission of the woods natural resonance. Obviously, the thinner the material, the lower the dampening effect, but also as the material is different to the wood undergoing repair, the less of it there is, the easier it will expand and contract in an entirely natural manner, along with the material it adheres to. This is what we really want. The most finely engineered solution possible.

It mends, supports and prevents, but does so by way of the most minimalistic, finely engineered solution achievable. That is the essential point.

 

To be honest.

Although Laminated Acoustical Products are today looked down upon as against Solid Wood Products, for reasons we all understand.

It has long been my view that Solid Wood Products being so vulnerable, often can benefit from a superlatively engineered, minimalistic form of structural support that could be thought of as a type of limited inner lamination. There is a History of this fitted within American Guitars everyone here should be familiar with, both utilising Wood and Material.

However, I am convinced that Guitar Design could be greatly improved in future, by using neither a completely Solid Wood or a Laminated Wood Design, But by a Hybrid Design that drew from the best attributes of both types of Instrument. One that allowed the greatest vibration possible but provided the strongest support, but in the most minimalistic, discretely engineered way. 

For instance, one could take a piece of metal and punch holes right through it, the effect of which would be to give it a far, far higher tensile strength. It would be firmer and stronger as a result. Your car is full of these. I am yet to be convinced that finely crafted, complex structural designs, could not eventually provide the type of support that greatly evolves what is traditionally thought of, as THE way to make a Great Guitar. I think there's a whole lot of development that could create a new future for the evolution of the Guitar.

It's just a question of proper resources in Research and Development. What I am writing about, is Guitars that utilise the very latest technologies and materials in their underlying structures. Enabling economical construction of far better, mid priced Instruments, that compare tremendously favorably to High Priced Traditional Solid Wood Instruments, (not replace them), yet are far superior in sound to today's Laminates.

To bring both ideas together cost effectively, by utilising pre formed internal structures and in looking in a new way as to how we make Affordable Quality Guitars in the future. It needs a lot of work, to bring it from where it is at present, as a novel, High End Alternative, but I believe a breakthrough could be achieved, but only given the right resources.

Most Guitarists are traditionalists by nature. But there always are the Innovators at the edge of something new.

 

P

[Paul Breen]

Hesh,

Thanks for your thoughts and the time it took to present them. I would not have posted this thread if I was concerned about anyone not quite seeing things my way. The dialog is rolling along as it should in a forum format, with both pluses and minuses being aired out. Learning repair techniques, properties of materials and how to correctly use them is a life long pursuit and I appreciate any help I can get along the way!

Frank and Eric, thanks for your observations.

Paul, it's 70 degrees right now and 46% humidity outside...my kind of weather! The forecast has us back up to 86 with an upswing in humidity by next Wednesday. : - (

Greg,

Tyvek? Really? I would think that Tyvek would not expand or contract at all with humidity swings, the other end of the spectrum but essentially the same concerns Hesh addresses. I have a lot of respect for Paul Hostetter's knowledge of instrument repair...Tyvek, interesting!

Peter,

Thanks for your lengthy post and sharing your knowledge of parchment!

Indeed, there are advancements in technology daily. We are in the midst of a modern techno renaissance, newly discovered materials and processes will surely find there way in a more dramatic way than we have seen, into an instrument building industry that is steeped in tradition.

[Greg Mirken]

That could be an issue, and for that reason I would not use a single large piece as you have, but rather circles of maybe 1" diameter positioned at points where cracks propagate, namely the tips of the noses and tails on your uke.