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Michael H

Crack cleaning, stubborn coloring not removable

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This cello has been with my go-to luthier that handles projects beyond my skills, which is more often than I care to admit. He has tried several ways to dissolve the black in the crack, but with no luck.  What are some options aside from picking it out?

 

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That looks like it's in the wood now. I'm not sure if there's any good ways to clean that out without removing varnish and having to retouch the whole way down. 

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Hard to tell, from the photo. What do you see when you raise one side or the other so you can see the entire gluing surface of both sides? Is it dark all the way across the surfaces?

If there's varnish or discolored epoxy all through the crack, you might be able to clean it by softening it with an acetone gel, a nitromethane gel, a "superglue dissolver", or a "varnish stripper".

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2 hours ago, David Burgess said:

Hard to tell, from the photo. What do you see when you raise one side or the other so you can see the entire gluing surface of both sides? Is it dark all the way across the surfaces?

If there's varnish or discolored epoxy all through the crack, you might be able to clean it by softening it with an acetone gel, a nitromethane gel, a "superglue dissolver", or a "varnish stripper".

These are great questions, but I do not have the cello in my hands at the moment.  Aside from a neck reset with ebony lined button, he has removed and re-cleated many of the cracks.  This photo is from before his work, but he mentioned the other day that he could not dissolve the black.  I may have to wait until it is on my hands again for an update on your questions.  I figured I would reach out and see what you guys could come up with and see if had already tried.

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I wouldn't want to be the one to do it, but first I would see about getting a microscope and refined dental pick, but I wouldn't have lots of hope for that and would probably deem it a waste of time and then be forced into thinking about excising the crack and dutching in a new long sliver that will "blond" out the crack to which it could be then made invisible with proper touch up techniques and materials. Not a job for the faint of heart.

edit; to elaborate, excise implies taking a razor sharp STAINLESS steel knife, and at a steep angle, cutting a "reed" widths knife "score" down the entire length of the crack, thus effectively cutting out the black and removing it.

Then a piece of Spruce must be found that has similar color and grain characteristics, a long angled sliver must then be cut to act as a long "cork" or "bung" that will "slot" into the slightly V shaped excise cut in the cello top.

Once the sliver is cut, it must be carefully coated with hide glue, allowed to dry and with a flash of very hot water from a brush in order to properly glue the thin v sliver into the excise gap , AFTER VERY CAREFULLY DRY FITTING AND ALIGNING THE SLIVER of course.

After the sliver has dried in, it must be leveled with the top CAREFULLY and the must be color matched in with the "right" varnish materials by the "right" guy

or Caulking and Paint makes us what we ain't :lol: 

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I can not remember where I got this from on removing or cleaning stain or dirt from cracks, so please feel free to correct or give input.  But string soaked in pineapple juice laid in crack has been used.

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3 hours ago, Alex l. Reza said:

I can not remember where I got this from on removing or cleaning stain or dirt from cracks, so please feel free to correct or give input.  But string soaked in pineapple juice laid in crack has been used.

String or thread soaked in one solvent or another (including water and citrus solvents) can be very useful.

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3 hours ago, Alex l. Reza said:

I can not remember where I got this from on removing or cleaning stain or dirt from cracks, so please feel free to correct or give input.  But string soaked in pineapple juice laid in crack has been used.

Pineapple juice does contain protease enzymes that would help digest things like glue or other protein matter.

ttps://en.wikipedia.org/wiki/Bromelain

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I have read here on MN that due to these enzymes, once pineapple juice is used it's difficult to glue surfaces together again.  but perhaps there is an effective way to clean out the pineapple juice so the crack can be closed again sucessfully...

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7 hours ago, violinsRus said:

I have read here on MN that due to these enzymes, once pineapple juice is used it's difficult to glue surfaces together again.  but perhaps there is an effective way to clean out the pineapple juice so the crack can be closed again sucessfully...

The sugar is what weakens the bond, it seems more water than I would care to use would be needed to wash it out. 

The ability for the crack to be cleaned has lots to do with how long it has remained with a crack that acts like a belly button and traps everything. Let alone what cleaners may have been used,any oils?, as well as the uv darkening "into" the crack.

If the crack has and or can be glued up so structural integrity is present, I'd probably call it good enough. Beyond the darkening it looks like the wood has puckered up a bit creating a valley into the crack, so even if it was cleaned it would probably still show as a crack.

I don't think I'd be throwing sugary juice into {the edges/glue surface}of a crack if you want to be able to glue it {on a violin as a sealer, ok}  

I still think the only way to make that invisible is to do the method I described, but I could be wrong, and if I am, please come back and tell us how it was done.

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On 9/15/2019 at 12:27 AM, jezzupe said:

The sugar is what weakens the bond, it seems more water than I would care to use would be needed to wash it out. 

 

I was under the impression it was the Bromelain (same stuff that's in many meat tenderizers).  I believe fiddle doug put up a link pointing that out.  Some schools of restoration use commercial meat tenderizers... though I do not.

Anyway, wish I had something helpful to offer concerning cleaning the crack, but I can't tell what it is that needs to be removed from this side of the screen. I have at least a half a dozen surfactants, detergents and solvents I empty from time to time... but there's always that ugly one that none of them touch!

If it can be successfully cleaned, and has not been scraped (which I think it may have been), there are certainly ways to solve the puckering, or potato chip, texture.

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17 minutes ago, Jeffrey Holmes said:

I was under the impression it was the Bromelain (same stuff that's in many meat tenderizers).  I believe fiddle doug put up a link pointing that out.  Some schools of restoration use commercial meat tenderizers... though I do not.

Anyway, wish I had something helpful to offer concerning cleaning the crack, but I can't tell what it is that needs to be removed from this side of the screen. I have at least a half a dozen surfactants, detergents and solvents I empty from time to time... but there's always that ugly one that none of them touch!

If it can be successfully cleaned, and has not been scraped (which I think it may have been), there are certainly ways to solve the puckering, or potato chip, texture.

My luthier has claimed that he will have the cello ready in about 1.5 weeks. At that point, I will have more info to give, but i am guessing that this crack will be left up to me, or someone else that I send it to. We seem to agree that it is a handsome cello, with a nice looking scroll, that it is older and that it has a label. Neither one of us are willing to claim much more than that at this point. :) Tone has always been my main concern. Origin may or may not become a factor with this instrument.

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From my experience "messing" with sugar, one of the problems,or not,as I could come up with applications, is that the sugar melts rather seamlessly into hide glue and in proportion,it can dramatically reduce hide glues bonding strength, but I'm sure the meat tenderizer enzyme does not help either.

I suppose it comes down to the value, either monetary or sentimental if someone would want to go all the way with it.

All I know is that if someone came to me with it I'd refer them to you.

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