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How much glue is needed on the top block facing the top?


Andreas Preuss
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My preference is still to use fresh hide glue which one has already had a lot of experience with, and dilute it with enough water if one wants to reduce the strength or increase the gelling time.

I am not yet understanding how one could get that level of predictability by using old glue, which has deteriorated to one extent or another, via various means.

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3 hours ago, stringcheese said:

I'll heat glue four times. First time for critical joints. It will have the best joint penetration, strength and the longest working time. Second time it will be thicker and shorter work time, so if I need glue that will fill a gap a LITTLE more. Third time I'll thin it and glue top seams. Fourth time I'll clean the glue pot.

I don't think you gain anything trying to fill gaps with hide glue. What gaps are you trying to fill the 2nd time? For hide glue to work well your joints have to fit. Good proctice anyway when making violins.

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3 hours ago, David Burgess said:

My preference is still to use fresh hide glue which one has already had a lot of experience with, and dilute it with enough water if one wants to reduce the strength or increase the gelling time.

I am not yet understanding how one could get that level of predictability by using old glue, which has deteriorated to one extent or another, via various means.

I don't keep glue too long, so "old" is probably a little deceiving, and refrigerate between uses, but it tends to change properties in a pretty predicable manner as it is reheated.  Bone glue tends to hit the mark fresh and thin... but keep doing whatever you're doing.  Your tops come off pretty cleanly in my experience.

 

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5 hours ago, David Beard said:

This is what I'm getting at.  Cennini often warns about things where he sees a need.  And it is very easier and natural to let a water bath get to a hard boil.  So it doesn't seem to me that he likely shared that concern.   Maybe that particular concern was just invented by a thermostatic gluepot salesman?

I too know that steam is much hotter.  If you let the water boil down bellow your inner pot, then the steam can lead to much hotter temps.

I know that on occasion I've done that. And each time I've thrown the glue out think 'that must have overheated'.   But, on these cases, I could never see anything wrong with glue.

And, many times the water has hit a hard boil for stretches of time.  Usually then I haven't thrown the glue out.  And I've been able to see and issue.

I can see clear issues with old glue.  

But I'd like to understand how to tell if some used glue has been ruinned from overheating.  

If I put it in kiln and turn it to ash, I can tell.  But short of that, does anyone know what goes wrong and how to spot it?

If you had it in the pot and it ran out of water it is starting to over heat. If it still solidifies after cooling down I guess the over heating was not too long. Otherwise it probably depends on what amount of glue you are cooking. Small amounts seem to be riskier than big amounts. Otherwise it certainly depends on the type of glue you are using.

If it is really ruined it doesn't solidify any longer when cooling down. But now I am not sure if this is the answer to your question. 

Otherwise I noticed that one and the same glue behaves differently I different climates. I had a big batch of rabbit hide glue I bought when I was working in Germany. I used it in NY and it was fine (still working with a regular hot plate) and when I came to Japan I had more often liquid glue in the jar. This became the reason to look for a better more controlled heating element and now it happens not so often any more.

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I guess the point I was trying to make is that you can reheat glue, but the properties of the glue will change, and you'd better not expect the same results. I have to do some down and dirty repairs on student instruments, and I may try to get away with stuff that I wouldn't do on something better. If I'm working on something decent, it's fresh and prepared appropriately. The second heating (done carefully) will be strong but not as workable. The third will work in an emergency. The fourth, clean the pot and start over.

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1 hour ago, stringcheese said:

I guess the point I was trying to make is that you can reheat glue, but the properties of the glue will change, and you'd better not expect the same results.

I agree.  Every time I reheat glue, the properties change. I would shudder to imagine how much that can change with glue which has been heated for a long time,  repeatedly reheated,  or has mold growing on the surface.  Such examples are far outside the boundaries of the the sort of consistency and repeatability I'm interested in.

 

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  • 7 months later...

That's where we hide the microfilm :lol:, personally I think your trying to find a solution to something that's not really a problem. Keeping in mind in your original post you blamed the problem on some type of glue that was not hide glue, which is a /the problem. Furthermore related to "getting something started" I rarely go for the knife as far as opening the seam goes, I will use a tapping block after scoring the varnish, tapping usually opens the area up enough to easily get a knife in there. Keeping in mind when we whack the butt end of a cross cut, the material is at it's strongest structural orientation and well you can really whack it if needed as long as you are using a nice soft tap block so as to not mar or dent the material. The hide glue is at it's structural weakest when "pull apart" force is applied,or whack force, which also exploits hide glues ability to shatter as it's bonding strength is at it's weakest when that type of sudden force is applied.

Personally I don't think anything is broke so I don't see a need to fix it.

And lord forbid someone other than me works on one of my instruments I don't want to make anything easy for them, I would want someone who is super qualified and doesn't find challenges challenging. I consider them lucky that I don't place land mines in there :lol:

The difference between an adventure and an ordeal is ones attitude.

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2 hours ago, jezzupe said:

personally I think your trying to find a solution to something that's not really a problem

I have seen and restored enough instruments to see that much damage simply starts from the borders and there the most damaged zones are at the upper and lower block. 

I have no intention of convincing you to use my method. I am simply posting here ideas for those who are interested in it. 

2 hours ago, jezzupe said:

I rarely go for the knife as far as opening the seam goes, I will use a tapping block after scoring the varnish, tapping usually opens the area up enough to easily get a knife in there.

You mean you knock the borders to loosen the glue? Never tried that, but I would assume this works only if you knock on the endgrain of a spruce top. From the side the wood is presumably absorbing the shock.

Regardless, I can't see how you would make this work on the top block area.

 

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49 minutes ago, Brad Dorsey said:

Andreas,  I think this might be a good idea.  But if the groove got completely filled with glue, I don't know if that would that make top removal easier or harder.

Brad, if you get into a 'glue-panic' you will certainly be able to fill the entire groove with glue. ;)

 

But even then, glue shrinks with the evaporating water and chances that this touches the surface above is almost zero. And if you are REALLY worried about it you can make it deeper. IMO 1mm is enough.

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10 hours ago, Andreas Preuss said:

0F0C3CE6-9F14-479B-943F-FC2CA4A1F675.thumb.jpeg.9b8cbfed534aea5a36ea8a64c03eea53.jpegMy latest solution for this problem. 
I made a shallow groove on the top block at the neck, the area which is most difficult to reach with the opening knife. This groove is 6mm wide and about 1mm deep.

I'd hate to be looking for a buzz on this fiddle!  

Are those doubled linings?  Kantuscher once told me that he did that with the idea of stablizing the pitch.

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57 minutes ago, Philip Perret said:

I'd hate to be looking for a buzz on this fiddle!  

Are those doubled linings?  Kantuscher once told me that he did that with the idea of stablizing the pitch.

A buzz usually comes from two surfaces in close contact, so I have no worries here.

The doubled linings do stabilize the pitch. I had made a viola a few years ago which had at the beginning a problem with a dropping neck. When the customer came back after I had already done a raise pitch one year earlier, I decided to open it up, make double linings only at the top side of the upper bouts. Recently the customer came back and the pitch was just dead on the previous measurement. 

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6 hours ago, Andreas Preuss said:

I have seen and restored enough instruments to see that much damage simply starts from the borders and there the most damaged zones are at the upper and lower block. 

I have no intention of convincing you to use my method. I am simply posting here ideas for those who are interested in it. 

You mean you knock the borders to loosen the glue? Never tried that, but I would assume this works only if you knock on the endgrain of a spruce top. From the side the wood is presumably absorbing the shock.

Regardless, I can't see how you would make this work on the top block area.

 

I think it was Nathan S. who posted a tutorial on "knocking off a top" , not sure, but it was one of our members here. Perhaps someone here has a link to it. It really is the better way to go with much less damage and much better grain/key locking when it goes back together based on the way the two pieces will be separated, a knife is separating the seam, with push through the seam and cutting through grain fibers, whereas knocking it off cleanly separates the fibers and leaves behind an easy to mate separation of the two parts, with generally much less damage. Yes of course you don't want to knock the side grain, but even the points in the crotch of the curve can be lightly tapped, thus releasing the corner blocks in most cases.

I suggest making some very strong glue and to glue up a lopsided T so as to mimic a top/rib section and then test knocking it off, even with very strong glue mix you will see the top separate as this is the one force direction the glue is weakest in, particularly if the "blow" is just right, it seems to shatter the glue seam.

Admittedly it does take time to develop the feel for it, and the "just right" hammer and tap sticks must be used, but I think you will find it works great.

Also with your divet I concern myself with some future repair guy's knife finding that hollow and then digging up the block more than needed as he "thinks" he's dealing with a standard full block. Also potentially squeeze out making glue "stalactites" that could induce a buzz.

I would think one could achieve a similar result as what you are doing with a very thin piece of tape that would prevent wood to wood gluing contact.

 

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Popping off a contemporary violin top, glued with hide glue, even when it's glued with strong mix, is just fun and not difficult at all.

What restorers do when opening a valuable old one, is something completely different. If they knock them of they are daredevils.

It would be very interesting to observe restorers at work. I could sit and watch for days.

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40 minutes ago, Peter K-G said:

It would be very interesting to observe restorers at work. I could sit and watch for days.

They will spend a day, an evening, or even a night hour taking off that top. Maybe faster with no one around to disturb them. Two-three spatulas, one round, a small bottle of alcohol + goggles, lots of patience and focus.

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10 hours ago, Anders Buen said:

They will spend a day, an evening, or even a night hour taking off that top. Maybe faster with no one around to disturb them. Two-three spatulas, one round, a small bottle of alcohol + goggles, lots of patience and focus.

That is true. However, some tops might require a large bottle of alcohol : expensive violins demand very steady hands.

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17 hours ago, jezzupe said:

I would think one could achieve a similar result as what you are doing with a very thin piece of tape that would prevent wood to wood gluing contact.

 

That's what I like about discussion boards. One comes up with an idea another participant finds a better or different solution. Tape could work, but since I have the groove already there I could fill it with a 1mm plastic sheet.

Concerning glue tear outs I found the most bizarre things in apparently bad repair work but it was never the cause for a buzz. Even a loose bass bar didn't make that and I have seen one.

(Maybe time for a new thread about buzzes causes and cures.)

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Speaking of using alcohol to remove tops, do any of you chemists know a cheap and easy way of removing excess water from an alcohol container which has been opened too many times? Would suspending dried silica gel over the liquid accomplish anything? Or some kind of hygroscopic salt?

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49 minutes ago, David Burgess said:

Speaking of using alcohol to remove tops, do any of you chemists know a cheap and easy way of removing excess water from an alcohol container which has been opened too many times? Would suspending dried silica gel over the liquid accomplish anything? Or some kind of hygroscopic salt?

I once asked a chemist the same thing, he told me that anhydrous sodium sulfate is what they used in the chemical laboratory for the same purpose. It must be left to act for a few days but it works.

Confirmed by Wikipedia :):

"In the laboratory, anhydrous sodium sulfate is widely used as an inert drying agent, for removing traces of water from organic solutions.It is more efficient, but slower-acting, than the similar agent magnesium sulfate. It is only effective below about 30 °C, but it can be used with a variety of materials since it is chemically fairly inert. Sodium sulfate is added to the solution until the crystals no longer clump together."

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2 hours ago, David Burgess said:

Speaking of using alcohol to remove tops, do any of you chemists know a cheap and easy way of removing excess water from an alcohol container which has been opened too many times? Would suspending dried silica gel over the liquid accomplish anything? Or some kind of hygroscopic salt?

Also not a chemist. Have you looked into molecular sieves (3a)?

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