I absolutely HATE people who sit around having opinions about what they once read about someone saying something about one matter or another, and then putting this out there to see what other people have to say about it...... "Ohhh is it true or is it not true etc., etc., etc."
It reminds me of the never ending commentary - like I am not a huge fan of Micheal Jackson - never was... but I cranked on the TV and decided to watch his funeral - simply because it was on.
And I would have been happy to have sat there and watched the whole thing - in reflective silence..... but could the TV networks do that? Nooooo way - they had an endless stream of chat show hosts and interviews...... and they just had to be yammering and yammering and yammering away, non stop with anyone and everyone and all the details and gossip and on and on and on and on they went...
So I just turned the TV off.......
Anyway - I am not much into "opinions and speculation" - because they **** me and so do the people holding them.
I do stacks of wood work - and I got (back?) into using collagen based adhesives for binding up the thousands of pages of manuals I had to make in furthering my own interests - and these glues are composed of gelatin, glycerin and some water and some vinegar.
It's like making a rubbery glue and it makes GREAT book binding adhesive - along the spines of books....
And since I am an utter tight arse and I don't really want to cough up large amounts of cash for minimal results or quantaties - I decided to start using plain food grade gelatin in the construction of my instruments and cases (all sorts of instruments - not just musical).
Now I prefer scientifically conducted tests over opinions anyday - but here is what I have done and found - vs what I know should be done.
I tend to love using glue - and LOTS of it.... everywhere. I tend to buy it in bulk and I used to like using PVA - BUT:
Because I live in the middle of nowhere and the local merchant either has none - or they charge heaps for it when they do get it in; I have kind of gotten a bit sick of the unreliability and or pricing of the agent.. so I am tending to prefer to steer around the supply problem - by using bulk quanties of granulated gelatin - shipped in 2.5Kg lots straight from the factory.
I have found that ordinary Gelita Brand - food grade gelatin (in Australia), to be both very hard and a very very strong adhesive when bonding timber.
In a few "special joints" I have applied a thick external bead of it (thick glue), around the outside of the joints, like welding reinforcement on pipe to plate welds....
The glue has dried VERY VERY hard - sort of like the clear HARD epoxies that they use to encapsulate clear LED's with.
On other lap joints etc., the bond has been so strong, there is NO way that joint is ever coming apart....
I like heating my glue on my own glueheater and being a silly old man, talking to myself and making tut tut noises like an old motorbike and having everything just so.... and preheating the timber joint etc., and coming away - overall - being very pleased with myself and the assembly at hand.
OK to get away from opinions and into proveable facts.
There is NO doubt that when very high strength glue is needed, on very fine and highly stressed parts - that high strength glue MUST be used.
BUT what I like to see happen, is that rather than people express opinons about other peoples opinions - I'd rather see YOU get off your arse and perform some tests - and then come back and tell us all about your results.
What I'd like to see done, is for say 24 little blocks of timber to be cut from 3 or 4 "across the range" of timber types, from the same areas, with the same saws and surface preparation etc...
And for each of the timbers to be glued with 4 types of collagen based glues, in a way that tests the bond strength of 1 or 2 cm2 of glued joint area; in tension and in shear, of both the end grain and in parallel to the grain joints;
Using the same glue strengths of say 50:50 (dry glue weight and water); and all the joints be given the same clamping, drying and hardening time; and then to have the joints tested to failure on a calibrated tension machine - at say 12% relative humidity at 20*C...
And then to run a series of identical tests in a heated and humidity controlled chamber - at say 40*C - in dry heat and then in slowly increasing levels of humidity of +10% relative humidity every 12 hours - up to saturation point... at a tension of say 50% and 75% of the dry cool specimens failure point - for each specific glue.
The other issue that must be taken into consideration is the joint's surface area and the relative required strength of the bond - and is the bond strength primarily being made to resist tension, shear or peel?
While I have NOT actually tested the bond strength of Australian Gelita Brand "food grade" gelatin; in a static rig with a tensionometer (?), I do know that in hammer and 2 bits of glued wood in a vice test; that this stuff is about 2 x as hard and as strong as PVA wood glue;
I do know that collagen glues have fairly definite "pros and cons" about them - like every other adhesive has - but it being easy to dismantle, reglue and clean up - really appeals to me; there is NO nasty chemicals and fumes used in it's formulation; and I kind of like all the "pissing around" to make a really well crafted joint when I do use it.
Setting aside the cost of the time to make it; I can make up 5 liters of this glue at 50:50 (weight for weight) proportions for about $60 - of the base material delivered to my door (huge advantage) fresh from the factory - where as quality PVA glue costs nearly double that.
Anyway.
Rather than having opinions - I'd be prepared to perform the said tests on the basis of people supplying the materials to do so.
What I want:
I want 50 pieces of EACH of ones favourite woods, to be made to exactly 20mm x 20mm by 50mm long, and a 20 gram sample of each of the "hide glues" and any other glues that you prefer to use; to be sent to me and I'll construct a series of tests to determine and publish a table of the results of each glues failure points - in regards to tension, shear and peel, at relative humidity and at increasing humidity under fixed tension.
So all you luthiers - send me your wares.
Email me for my address.