Jump to content
Maestronet Forums

Hide Glue - Gram strength: 192 or 315?


xraymymind
 Share

Recommended Posts

Hello all,

I need to order some new hide glue. In the past I have used 192 High clarity, and been quite happy with it. But I have heard of many other makers using stronger gram strengths - such as 251 or 315. 

Might I ask for a bit of advice as to what gram strength you (the reader!) might use, and why?

It would be especially interesting to hear from anybody who has experience of both 192 and 315 gram strengths... Which do you prefer, and why?

All the best.

Link to comment
Share on other sites

I've been using the same glue for 20 years unmarked but assuming it is in the 190's based upon water - glue ratio needed. Never had problems.

Generally, (from memory) higher strength glue needs more water for given viscosity and gels faster. Lower strength glue has less water, and longer open time till it gels. I'm not aware of any study that compares final strength of the joint when either of these glues is used. Folks tend to believe that gram strength equals joint strength but I don't think it is so straightforward.

Link to comment
Share on other sites

I use 251 for everything except attaching the top plate; for that I use old 251 (ie. reheated too many times) and diluted.

I use very dilute 192 for sealing prior to ground/varnish process.

I find 315 gels too quickly. Maybe I need to experiment more.

Link to comment
Share on other sites

2 hours ago, avandesande said:

I've had good results with the 315 that IV sells. I use 190 only for gluing on the plates. 1:4 weigh the glue and water by volume

Conveniently, water volume and mass are the same, 1 cc = 1 ml = 1 gram

Link to comment
Share on other sites

1 hour ago, Jim Bress said:

Conveniently, water volume and mass are the same, 1 cc = 1 ml = 1 gram

Yep, but not the glue:)

1 cc of glue does not correspond to 1 cc of water, even if 1 g of glue is equal as 1 cc of water. So use weight and not volume is more accurate.;)

Link to comment
Share on other sites

6 minutes ago, Don Noon said:

Gram scales are infinitely more accurate than trying to measure volume anyway.

But measuring liquid would be more convenient using a graduated cylinder, if infinite accuracy isn't required.

I don't like weighing water and I figure that your tolerances aren't that close due to evaporation, so volume it is....

Link to comment
Share on other sites

"Gram strength" of a glue is kind of a weird sort of measurement, which may or may not have much to do with the adhesion strength.

Basically, this test consists of mixing the glue and water to a certain ratio, and then inserting a probe into the resulting gel, and measuring the resistance of the probe penetration into the not-yet-dried glue. I am not yet seeing why this should be a determinant for us.

In actual practice, higher gram strength glues need to be more diluted with water to give adequate working time (when that matters, and for the most part it does), and more water dilution also reduces the bonding strength. So the difference between the bonding strength of 192 and 315 gram strength may be a wash, and which is superior will primarily come down to the skillsets of the user.

 

Link to comment
Share on other sites

From a manufacturer 

https://blog.lddavis.com/glue-101-gram-strength

Quote

The gram strength of a material is important in our industry because it correlates to the rigidity of the glue after the bond has been formed.   The higher the gram strength, the stronger the cohesive forces in the glue. Cohesive forces are the attractive forces between the molecules in the glue, so as the gram strength gets higher, the glue will stick to itself better. The bond will also become more rigid as the gram strength increases. 

 

Link to comment
Share on other sites

10 hours ago, Carl Johnson said:

The gram strength of a material is important in our industry because it correlates to the rigidity of the glue after the bond has been formed.   The higher the gram strength, the stronger the cohesive forces in the glue. Cohesive forces are the attractive forces between the molecules in the glue, so as the gram strength gets higher, the glue will stick to itself better. The bond will also become more rigid as the gram strength increases. 

They are talking about cohesion only but for us ADHESION is perhaps more important part of the joint. The layer of glue between the wood pieces is minimal so greater cohesion will not make much difference.

As I see it (but never tested it) is that high strength glues are mixed roughly 1:4 with water while low strength close to 1:2 for similar working viscosity. This may mean that after clamping of the total volume of diluted glue that remains "trapped" in the joint twice as much molecules of the lower strength glue remains than of the other to hold the pieces together when the water evaporates. This also means twice as much shrinking for higher strength glue. That may help to draw the pieces together but if we look at wood as budle of straws with voids on the surface this can lead to more mpty spaces - starved joint if the clamping pressure didn't allow just about right amount of glue to stay in.

 

Link to comment
Share on other sites

10 minutes ago, HoGo said:

They are talking about cohesion only but for us ADHESION is perhaps more important part of the joint. The layer of glue between the wood pieces is minimal so greater cohesion will not make much difference.

As I see it (but never tested it) is that high strength glues are mixed roughly 1:4 with water while low strength close to 1:2 for similar working viscosity. This may mean that after clamping of the total volume of diluted glue that remains "trapped" in the joint twice as much molecules of the lower strength glue remains than of the other to hold the pieces together when the water evaporates. This also means twice as much shrinking for higher strength glue. That may help to draw the pieces together but if we look at wood as budle of straws with voids on the surface this can lead to more mpty spaces - starved joint if the clamping pressure didn't allow just about right amount of glue to stay in.

 

Good point.

I am convinced that almost every glue strength (with good long protein chains not broken) if used properly can give functionally satisfactory results, it is simply a matter of knowing them well and correct the dilution according to the results and types of gluing. Testing is the key, and relying on your own personal experience first of all.

Link to comment
Share on other sites

Frank Ford - one of best restorers in guitar world - uses and recommends high clarity 192 g.s. glue.

here:

http://www.frets.com/FretsPages/Luthier/Data/Materials/hideglue.html

Some of his comments may be frowned upon by violin makers, but his experience and results are well respected among guitar folks.

Link to comment
Share on other sites

I have tried 315gs but apart from these tests have always used 192 high clarity. Mixed to give approximate open times similar to what David B’s article recommended. Plenty of strength for any instrument making application.

Link to comment
Share on other sites

14 hours ago, Davide Sora said:

Good point.

I am convinced that almost every glue strength (with good long protein chains not broken) if used properly can give functionally satisfactory results, it is simply a matter of knowing them well and correct the dilution according to the results and types of gluing. Testing is the key, and relying on your own personal experience first of all.

I agree Davide. I will use 192 on most things, and I use "older" and/or diluted 192 for tops.  As someone who is constantly removing plates, I won't glue belly's with full strength 192.  I will use 315 on things like broken scrolls, neck etc ASSUMING that the working time of the situation will work.  The 315 is not good if it starts slightly gelling early.  The strongest joint (IMHO)is the one that you get the best penetration and the glue can really get into the wood (viscosity).  For me, I only use 315 when I have plenty of exposure to the glueing surfaces.  This is bigger than the G strength.  I think this is what Davide is getting at.  

Link to comment
Share on other sites

I think use of higher gram strength glue would be to advantage in joint that for some reasons are impossible or impractical to clamp an dcan be held by hand till the glue grabs and left to dry undisturbed, like the Jacob Saunders' method of gluing broken scrolls - apply glue, hold the scroll precisely in place and count 50 sheep and let dry in position that doesn't add stress to the joint. I've used this method for broken mandolin scrolls.

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...