I made a small batch (1/2 oz glue to 0.9 oz water) of Milligan & Higgins 192 gram strength glue. I followed Frank's quick method for making the glue. I stirred the granules and water together, let it sit for about an hour, at which point it looked like fish eggs. Then I cooked it in "double boiler" to 140 degrees. It looked pretty good and it had the consistency it should. It's thin but not too thin, it's somewhere between what and good maple syrup.
I decided to test it on two small scrap pieces of mahogany. They both have been sanded, so you don't really feel the grain so much when touching them. Anyway, glued them up (grain perpendicular) and clamped them overnight. I couldn't break the pieces apart with my hands the next day, but I was able to when I held one piece with pliers and tried to pry the other piece with another set of pliers. I should note that the piece broke not because I pried it, but because I put pressure perpendicularly to the grain, which made the piece "fold" and break. The break was very clean with no splinters or fibers sticking out.
Because I'm new to hot hide glue, this test seems inconclusive and I'm not sure what to make of it. So I wonder what are some ways people here use to test their glue?
When I first tried to use HHG, I didn't know anyone that used it and didn't have access to any advice on the subject. What I had was a can of granulated glue bits that smelled funny. The can it came in included instruction for preparing it for use. (Note that I placed a "full stop" at the end of that sentence.There was nothing about how to actually use it.) Following the instructions, I made it up a batch and the results were OK when I used it for the first time. After that it didn't work so well anymore. ( BTW, it's not particularly funny or cool when the chair you fixed falls apart with your mother on it.,, even if you think it is. Just take my word for it.)
It took a while but I started figuring out how to work with it. Although I did learned how to cook it and work with it the whole thing was pretty frustrating and not nearly as linear as I'm making it sound here. The result is that I think I have a better understanding of how to use it than I would have otherwise.
I'm not saying to ignore all the information available now. I'm saying that experiences vary just like the working environment varies from person to person. The information that's out there can save you a lot of time and trouble but what's important is to learn how it works when YOU use it. Experimenting with blocks isn't a bad place to start if you're concerned about basic handling but it's probably not going to tell you all that much about how things work when the glue surfaces are not straight and flat or how to get a clamp into place on a curved/rounded part. My personal opinions is that you will learn more quickly if you got a junker guitar from somewhere to take apart and put it back together using HHG. Doesn't matter if it holds up or not if you learn how to use the glue in the process. You may even be able to get more experience if you want to return to what failed to hold up and repair it again once you get the hang of using HHG. The point is for you to learn how to work with the glue.
One of the opinions that I've developed is that HHG is actually somewhat more forgiving then most of the information we read indicates. If I want the joint to be as strong as possible, I do think that follow the rules closely will insure that. Heat the glue surfaces and have the clamp up material ready and waiting. ....the results will be a very strong joint.
But my reality is that I'm cooking my glue in a pot in my garage. The RH is something I check on the weather channel and my technique for controlling it boils down to a "work today or not " decision. There are a lot more issue in my work than if I'm optimizing the glue joint in every instance. I would probably be better off using something more modern but most of the instruments I work on were made with HHG and I have just enough ego to think that some of my work will last long enough that some future hobbyist might want keep it going. If that happens, I'd really like to have them think kindly of me so I try to avoid introducing too many "gotcha's" in what I deliver to them, thus HHG . Besides, I actually like working with it now.
I suppose I'm saying is that we should probably consider that every glue has an a set of optimum working parameters. Holding to those as closely as possible is desirable IF you have the wherewithal to do so to. Fortunately for me, most glues we use today will actually work at a high percentage of their max performance even if I miss their strike zone by a bit. Some of what I glue with HHG is not as critical or as stressed as other parts. I'm really not nearly as concerned about the splints/braces that I add to the sides of the old guitars I restore as I am the bridge or neck joint. Most of these instruments didn't have any support/crack control to begin with and the addition I make is just a bit of insurance for an old dry guitar side. I'm not likely to heat the parts before gluing and I may not have a clamp waiting in the "almost" position. If I take slightly longer to get a clamp in place and the glue is starting to gel just a bit when I get it on, I'm not going to loose sleep. It's not the strongest bond but it's enough for the job. Some glue joints are just more important then others The line may not be wide but there;s a bit more room for error on that joints that aren't so critical/stressed. That little bit of room can make it a lot easier to work with the glue in some instances.
It is important to learn how to use HHG. It's an archaic form of glue by today's standards and it's not as forgiving as modern glue but I honestly don't believe it's as unforgiving as we often think. It's been in use for a very long time and I don't believe that all of those joints and veneers were done with perfectly prepared glue used under ideal conditions. The glue is still around and in fairly common use today because it works well AND because it's not impossibly hard to use. You just need to learn it's "particulars" and using it on something "real world" will teach you faster than anything else.
( Please Note; No animals were harmed within sight of the poster, during the production of this post. The poster is in no way responsible for what may have happened beyond the confines of his "sight". All opinions are subject to review even if there is not possibility of change. Any resemblance to or reference of real people, living of dead, is possibly coincidental and, probably inadvertent, with the exception of the poster's reference to his Mother. In that particular instance, She was very real and VERY "advertent".)
You want to know and learn a few things about hot hide glue, talk to some good violin repair people. Hot hide glue is all they use.
The truth be known it's not that difficult to learn to use successfully. I've always mixed it water thin no matter what the application, too thick is a major problem in my opinion, it just needs to be slippery between your fingers. Warm the parts to be glued and you will have good success with it.
I've never experimented with gluing a joint and trying to break it once cured, but I have glued just about any joint you can think of, and had very few failures in over 40 years of using this glue.
After reading a few other replies, it seem people make a big deal out of the glue/water ratio and having everything just perfect and having a masters degree in it's use. Anyone can use this glue successfully.
If I was to stress one point, it would be to mix the glue water thin, too thick you will always have problems.
The consistency of thin maple syrup is best, or slippery between your fingers.
It's axiomatic that doing stuff right from the beginning and understanding why you do what you do is important to both tradesmen and artisans alike. If everyone could use glue successfully we wouldn't be using time pointing out the correct way to go about it and the things that affect it. Nor would Frank have to do tutorials on it's use.
You are obviously entitled to have your opinion about those who strive for perfection or who have a tertiary qualification or a background in science or engineering or luthiery but I don't see that as being any "big deal" - it's simply a way to establish ones credentials in the various areas we discuss here.
Similarly, Violins are to guitars as apples are to oranges - over-engineered, short scale, low tension joints in violins are not under the same stress as modern long scale 6, 7 and 8 string instruments with steel stings and skinny neck sections etc. Hot hide glue is all violin makers and repairers use because it is traditional and all they need to use. Not to say they are Luddites, they simply don't need high performance adhesives or practices in their repertoire.
HHG is alway good for a host of posts.
Appreciate your thoughts. But, how to use HHG is not a big secret nor do you need a whole lot of training.
Of course violins and guitars are different, but they are both made out of wood and held together with glue. As far as mixing HHG, applying, and clamping, they are the same for whatever instrument they are use on. Besides you strive for the most solid joint no matter what the instrument, that's my plan anyway.
This idea of using different glue/water ratios for different applications I've found not to be true. I use the same glue/water mixes for all joints. That is why I mix it, "water thin".
Now if your going to do surgery on the human body, you need extensive training. Some things are much simpler to learn and do right, and using glue is one of them.
My occupation was a Wild land Fire fighter for the state DNR, Forest Management Div. All my fire training was on the job, and I had no college degree. When the state needed more people to do timber inventory, I had OJT for that too, and did that job satisfactory, where generally you needed a forestry degree.
So, it boils down to the fact there are many things you can learn and do without extensive training or a college degree.
Forgive me please in so much as I have not read every reply in this thread so I may be redundant at times....
First the overall impression that I received reading the first page of this thread was that some folks, not all... are making this WAY more complicated than it needs to be...
Picture this: A factory back 40 years ago in Kalamazoo, Michigan where the workers, Gibson folks, had hot pots running all day (and likely all night too forgetting to pull plugs...) with a mass of HHG in them, a couple of brushes, and the "limited" knowledge that it actually takes to use HHG properly.
They would prepare a joint (and not always well either...) and "slather" it on say the bottom of a brace, position and clamp endeavoring to do so quickly.
The primary concern when using HHG and I am speaking of the real deal stuff say from M&H and never that awful Franklin bottled rasta imposta stuff is the very short open time.
As such one needs to have things set in place, parts, clamps, etc. in approximately 15 seconds or less. Any more time and with out using one of the methods to extend "open" time one risks a compromised joint.
With this in mind consideration needs to be given to where to use HHG as well as how to use it and again none of this is difficult to understand once you work with the stuff every single day and have success in doing so. A great example of where to use HHG in my opinion is any joint that needs to perhaps be "serviceable" in time such as gluing on a bridge. Personally I'm hip to the very thin, microscopic glue line resulting AND the very hard, crystalline nature of dried HHG believing as I do, for now... that it's sonically superior in applications that have sonic impact.
With bridge gluing we also have to observe the shortcomings of HHG meaning that our bridges need to be excellent fits with no unnatural acts required with the clamping, positioned in place quickly and the clamps snugged up before the stuff starts to jell.
Dry runs are your friend with HHG or any glue for that matter....
For me it makes perfect sense believing in the qualities I've mentioned so far to use HHG for all braces, bridge plates, bridges, etc. where we want the tone woods to interact well with as little dampening as possible.
The violin maker was "sizing the joint" as per the OP's post which although I see no harm in it is not at all necessary with HHG AND not how the vast majority of HHG users (dead or alive) use or used it.
Again the beauty is that if your chops are down, your parts fit, your methods sound, your experience positive, and you are mindful of working time you simply slather it on, clamp and Bob's your uncle. Man that Bob guy gets around...
Regarding viscosity I disagree with one comment that I read here that indicated that it does not matter. Typically viscosity does not matter all that much unless one is seeking a creative way to extend open time for an application that requires more open time no matter how good your chops are. For example gluing on a back plate on a new build in a go-bar deck. For me I am positioning 30 plus go-bars (and trying hard to not get hit in the face if one slips...) as well as some clamping cauls to protect the plate from the go-bars. Although it's arguable if HHG has an advantage in this application we HHG snobs nonetheless endeavor to use HHG in this application for the same reasons that man (or woman) climbs that mountain. And no it's not because we are stupid... although that can be true... it's because HHG is what we may have handy and ready, something we are comfortable with, it's tradition in guitar building, and some believe that for gluing on a back plate it' sonically superior.
For this application a higher gram strength has the added draw back of jelling even quicker so why would one use a higher gram strength for gluing on a back plate in a go-bar deck? Because according to Mario P. aka Grumpy and tested and confirmed by me as well you can lay down a thick bead on the rim that remains a bead and does not flatten out as quickly as regular strength HHG. The bead becomes self insulating to a degree with the most exposed walls of the bead starting to jell but also protecting the runny liquid HHG inside the bead from jelling. Position the plate, the go bars, etc. and you just extended the open time and applications for HHG. Some preheating of the rim is advisable too. When the clamps are positioned that bead is smashed and the runny, still hot HHG spreads out. This is a rather brilliant trick that many of us learned from Mario/Grumpy.
For bridges we have a method that can have all of the clamps in place in under 15 seconds. But if I am feeling pokey, and I often am..., I might pop the bridge in a microwave for 15 seconds so that the warm bridge will also extend the open time of the HHG.
HHG is easy to use, easy to understand but it does have limitations and if you don't pay attention to things such as open time it will bite you.
Regarding joints - recently I read on another forum a post by a member who insisted that HHG had great gap filling capabilities. WRONG..... Buzzzz..... resubmit in 30 days and try again....
HHG sucks at gap filling and IMO is not even as good as Titebond original which is a fine glue by the way too but also not billed as a gap filler!
HHG joints require superior joinery and attention should be paid to one's joints if using HHG. Again that microscopically thin, molecular level bond also comes with the price tag that it is no substitute for poor joinery and workmanship.
Regarding a sanded joint vs a freshly scraped joint the thinking is that sanding creates dust and contamination that interferes, at the microscopic level with a complete wood-to-wood bond. As such it's believed that a freshly scraped joint has more "joint energy" for lack of a better descriptive term.
So again picture that nasty old glue pot that has not been cleaned in ages because no one wants to do it, a couple of brushes sticking out of the pot, craftsman and women slathering it on to well fitted braces, clamping and moving on. And never, never, never forget the idea and need for serviceability so that your creations can be easily serviced in the future should Mr. or Mrs. Customer screw up and sit on the thing.... because they will and do.... often....
By the way there are examples of Egyptian furniture assembled with HHG that are 2,000 years old that are still doing fine. It's great stuff and part of the greatness is the ease of use within the stated limitations of course.
Lastly wouldn't it be great if there was a glue that for applications such as a loose brace in say a mando where we can't get an arm in there to clean out the failed glue that some new glue and the ability to reflow the old glue would get the job done? This is yet another attribute of HHG, it can be reflowed in time. Great stuff.