Jump to content
Maestronet Forums

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


Andreas Preuss
 Share

Recommended Posts

I was taught to always be sure to clamp the plate to the blocks when putting the top back on because of the risk of damage to the arching. Although this is the first argument I’ve seen for leaving an area of the block free of glue, a former colleague surprised me one day when he told me he’d stopped using clamps on the blocks when he put tops back in place. He still applied glue as normal, but he felt that clamping the joint would compress the contact point, making it a lot harder to fit an opening knife in later on. I’ve wondered about his theory ever since, but I haven’t been willing to test it out. I know what results I can get putting the top on the conventional way and don’t want to risk catastrophe.

Like Michael Darnton and Mark Norfleet, I’ve seen a good number of instruments that suffered structurally as a result of bad glue joints at the top block.  

Link to comment
Share on other sites

  • Replies 83
  • Created
  • Last Reply

Top Posters In This Topic

15 hours ago, Salve Håkedal said:

When I make new instruments, I do 2 small tricks:

Cut a very small chamfer at the edge of the block.

When I size the block with glue, I don't go quite to the edge.

If I use thin enough glue for the final gluing, it will soak into the wood where it's not sized. So there will not be glue squeezed out at the edge of the block. And the tiny slit from the chamfer will lead the opening knife in position.

kloss.jpg.08e4eca4d8730ae0e7dc464cbc0539c5.jpg

Yes! I always chamfer the inner edge of the upper and lower block on my instruments and unless the instrument has some historical value I will do so on repairs as well. I also use extremely weak glue for tops but do apply an even application on all the glue surface. I find that using old deteriorating glue is better than just thinning fresh.

Link to comment
Share on other sites

22 hours ago, Jeffrey Holmes said:

Agreed.  I will often use it if I've got it when gluing back a top.

That's not something that ever occurred to me. I often throw out questionable glue and make a fresh batch when gluing an important joint. Silly me! How do you guage when a batch of glue is properly crappy for the job?

Link to comment
Share on other sites

5 hours ago, HoGo said:

How do you know when the glue is just right and not deteriorated too much?

 

2 hours ago, bkwood said:

That's not something that ever occurred to me. I often throw out questionable glue and make a fresh batch when gluing an important joint. Silly me! How do you guage when a batch of glue is properly crappy for the job?

I heat the glue and use my finger and thumb to test the "tack" of the glue. Same method is used when using fresher thinned glue.

Link to comment
Share on other sites

19 minutes ago, Jeffrey Holmes said:

 

I heat the glue and use my finger and thumb to test the "tack" of the glue. Same method is used when using fresher thinned glue.

You can also smell it. A slightly unpleasant smell is good but if it won't gel stiff in the refrigerator it's too old. Ultimately the test above is very useful.

Link to comment
Share on other sites

13 hours ago, Jeffrey Holmes said:

 

I heat the glue and use my finger and thumb to test the "tack" of the glue. Same method is used when using fresher thinned glue.

Thanks. Are you sayiing old glue with less tack is better for the job than new thinned glue (it will be easier to break the bond)? I still don't understand the distinction you are making. Truly, it never occurred to me to intentionally use glue that was old, and I want to make sure I understand. Do you make a point to use old glue anywhere else, like for the whole top?

Link to comment
Share on other sites

4 hours ago, bkwood said:

Thanks. Are you sayiing old glue with less tack is better for the job than new thinned glue (it will be easier to break the bond)? I still don't understand the distinction you are making. Truly, it never occurred to me to intentionally use glue that was old, and I want to make sure I understand. Do you make a point to use old glue anywhere else, like for the whole top?

Yup.  When gluing back on a top I want a glue that has sufficient tack to be stable, but releases relatively easily when an opening knife is inserted. Older glue seems to do that best... but brittle glue (like bone glue) is very good, or thinned hide (I'd use thinned glue with lower g strength) works, but newer hide glue doesn't act exactly the same.  Still, that wouldn't stop me from using it if that's what I had (and it often is, as I seem to flush older glue out of habit). The only other application I can think of that I would use this type of glue would be the nut or temporary cleat.  Maybe Nathan has other applications that aren't coming to my mind at the moment.

Link to comment
Share on other sites

This is great to hear some varied in the workshop glue practices.

I'm curious if people have some simple 'in workshop' for determining if glue has 'denatured' or gone bad?

In modern literature, you hear lots of concern about keep glue temp from getting too hot, even keeping the temp below a hard boil.  But in old literature like Cennini, these concerns are conspicuously absent.  In deed, the old descriptions of making glue are basically to make a soup of your protein source and then evaporate off to a gel.  No cautions about not boiling.  The old source do show concern about over heating as they all describe a water bath heating to use the glue.  But not a concern about boiling.

So I'm curious.  How can you tell if a glue is bad from over heating?

Link to comment
Share on other sites

18 hours ago, nathan slobodkin said:

You can also smell it. A slightly unpleasant smell is good but if it won't gel stiff in the refrigerator it's too old. Ultimately the test above is very useful.

MN...the only place glue sniffing is encouraged...:ph34r:

Link to comment
Share on other sites

I have always rotated my glue sitting in the fridge based on age.  I use the same jars, and just switch the tops, one labeled "thin/Old".  When I want new fresh glue, I dump the "thin/old" glue out and make the new glue in that jar.  I then add a little water to the old fresh glue jar and switch tops.  Good to hear validation on the "old" glue for tops, always made sense to me, but now I'll admit to doing it:lol:.

Link to comment
Share on other sites

On 9/19/2020 at 2:02 PM, Don Noon said:

The appearance of blue-green fuzz all over the glue is a good indicator.

23 hours ago, David Beard said:

So helpful...

 

:unsure:

Actually, I DO keep glue around almost always until something grows on it.  Being "frugal", I figure I could do something with it until then.

 

Link to comment
Share on other sites

Just a little note on the "tack test" for anyone reading this thread who may lack experience. 

Thinned glue, suitable for gluing on a top, won't feel tacky between finger and thumb when you first apply it. But after a minute or so of holding finger and thumb together, you should feel a good, firm tack.

I only mention this because I've seen inexperienced builders discard glue that was actually perfect for top gluing because they thought it didn't tack quickly enough. And then proceed to apply glue that was strong enough to hold a nuclear reactor together.

 

 

Link to comment
Share on other sites

I am curious why fish glue isn't mentioned.  It would seem that it would be easier to manipulate/thin than hot hide glue.  I have only used it for a couple of years on 7 violins and a few guitars with no issues.  Should I be concerned about these instruments suddenly self destructing since HHG wasn't used?

Link to comment
Share on other sites

2 hours ago, woodbldr said:

I am curious why fish glue isn't mentioned.  It would seem that it would be easier to manipulate/thin than hot hide glue.  I have only used it for a couple of years on 7 violins and a few guitars with no issues.  Should I be concerned about these instruments suddenly self destructing since HHG wasn't used?

I have little experience with fish glue for instrument making, but I've heard it mentioned. Rabbit skin and fish glue were both used in the gilding process I believe, and conservation of gilded objects is the only experience I have had with fish glue.

Before I say the  following, I'd mention that the exact properties any animal glue possesses is dependent on the manufacture. All glues of any general kind aren't created equal.

My understanding is that fish glue (and rabbit skin glue) are generally more flexible in nature to hide or (especially) bone glues. It also has a longer set time.  We used some rabbit skin glue in violin making school, but I've rarely used it since, usually preferring hide or bone.  There is also a glue several of my colleagues like for restoration made from deer hide, which I believe is only available in Japan (or was).  It's nickname in Oberlin is "Bambi Glue". I believe sturgeon glue is commercially offered for instrument builders...so there are certainly choices that have been road tested.

This thread concerns gluing tops on, for which I would not choose to use a terribly flexible glue... which would complicate removal in the future... hence I and several others have mentioned hide and bone (more brittle) glues for this purpose.

 

Link to comment
Share on other sites

2 hours ago, Jeffrey Holmes said:

I have little experience with fish glue for instrument making, but I've heard it mentioned. Rabbit skin and fish glue were both used in the gilding process I believe, and conservation of gilded objects is the only experience I have had with fish glue.

Before I say the  following, I'd mention that the exact properties any animal glue possesses is dependent on the manufacture. All glues of any general kind aren't created equal.

My understanding is that fish glue (and rabbit skin glue) are generally more flexible in nature to hide or (especially) bone glues. It also has a longer set time.  We used some rabbit skin glue in violin making school, but I've rarely used it since, usually preferring hide or bone.  There is also a glue several of my colleagues like for restoration made from deer hide, which I believe is only available in Japan (or was).  It's nickname in Oberlin is "Bambi Glue". I believe sturgeon glue is commercially offered for instrument builders...so there are certainly choices that have been road tested.

This thread concerns gluing tops on, for which I would not choose to use a terribly flexible glue... which would complicate removal in the future... hence I and several others have mentioned hide and bone (more brittle) glues for this purpose.

 

Thanks for this information, I didn't realize the variety of animal glues out there or their uses.

Link to comment
Share on other sites

On September 20, 2020 at 5:01 AM, David Beard said:

 

So I'm curious.  How can you tell if a glue is bad from over heating?

One easy thing is: if you see your glue jar in your pot and the water has evaporated there is a good chance that the glue got overheated. ^_^

Otherwise I think 'overheated' is not quite correct. I have a pot for warming Japanese sake, so the temperature never goes above 60 degrees and this is much better than the regular pot I was using before. However the older the glue the weaker it gets even if it is kept warm at low temperatures. Thus seems to indicate that molecule chains detoriate no matter how, but with higher temperatures faster than with lower temperatures. 

I might make a test on this. I noticed that weaker glue gets darker even if the amount of water didn't change (though this is hard to say because glue us getting used in the meantime)

Glue which stays liquid is always dark. 

Otherwise I make a sort of quick check. When I take glue which has been used already out of the fridge I put my finger in it to feel how 'bouncy' it is. Not very precise because much water added can feel very soft. But if you maintain certain habits in keeping your glue this test helps a little. 

I keep at least three jars ready for every day use. 

Normal strong glue, preferably fresh.

thick glue for glueing bridge parchements 

brittle glue for glue seams. 

On each lid we mark the date when it was prepared and if we need weak glue just choose the jar with the oldest date on it. Thus has on a subjective measuring scale somehow the softest feel with the finger test and us darker than the other jars. 

Concerning the cennini treatise I guess that it was a sort of unnecessary topic to him, like 'everyone knows that glue just needs to be warm enough to get liquid'. In the other hand the use of glue for paintings serves a different purpose and doesn't need to hold a joint. Because the glue used for the gesso ground presumably was each time made freshly and used to the end this wasn't a matter to consider either.

Link to comment
Share on other sites

9 minutes ago, Andreas Preuss said:

One easy thing is: if you see your glue jar in your pot and the water has evaporated there is a good chance that the glue got overheated. ^_^

Otherwise I think 'overheated' is not quite correct. I have a pot for warming Japanese sake, so the temperature never goes above 60 degrees and this is much better than the regular pot I was using before. However the older the glue the weaker it gets even if it is kept warm at low temperatures. Thus seems to indicate that molecule chains detoriate no matter how, but with higher temperatures faster than with lower temperatures. 

I might make a test on this. I noticed that weaker glue gets darker even if the amount of water didn't change (though this is hard to say because glue us getting used in the meantime)

Glue which stays liquid is always dark. 

Otherwise I make a sort of quick check. When I take glue which has been used already out of the fridge I put my finger in it to feel how 'bouncy' it is. Not very precise because much water added can feel very soft. But if you maintain certain habits in keeping your glue this test helps a little. 

I keep at least three jars ready for every day use. 

Normal strong glue, preferably fresh.

thick glue for glueing bridge parchements 

brittle glue for glue seams. 

On each lid we mark the date when it was prepared and if we need weak glue just choose the jar with the oldest date on it. Thus has on a subjective measuring scale somehow the softest feel with the finger test and us darker than the other jars. 

Concerning the cennini treatise I guess that it was a sort of unnecessary topic to him, like 'everyone knows that glue just needs to be warm enough to get liquid'. In the other hand the use of glue for paintings serves a different purpose and doesn't need to hold a joint. Because the glue used for the gesso ground presumably was each time made freshly and used to the end this wasn't a matter to consider either.

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?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.




×
×
  • Create New...