Adhesives (Discussion)

In Lighly's topic Jason brought up an interesting question regarding the glue used for bone to wood adhesion... one of the above crossbows is an extreme example of such method. Therefore I'm also wondering what type of glue can be used in similar designs? Or even more...what methods/glues were usually used in such situations? hide- or fish-glue perhaps?

Ivo wrote:In Lighly's topic Jason brought up an interesting question regarding the glue used for bone to wood adhesion... one of the above crossbows is an extreme example of such method. Therefore I'm also wondering what type of glue can be used in similar designs? Or even more...what methods/glues were usually used in such situations? hide- or fish-glue perhaps?

Although hide and fish glues were common and really nice to use they are not going to be terribly moisture proof and I think this would tell when used for military and hunting bows. While a thick coating of shellac or oil boiled with litharge and later say about 15th century metal catalyzed boiled nut oil varnishes began to appear, may have provided some weather protection of the glued joints, it might not have been enough. I haven't had the chance to closely examine period pieces to tell or not. UV would cause the organic adhesives to fluoresce and there are other tests as well.

BUT, have you thought of lime-casein? Some of the oldest surviving furniture in the world (Egyptian pharoahs) was put together with this and it has remained in use throughout the ages in many parts of the world. Modern variants found use in water resistant applications for laminated boat hulls and earlier to put wood airplane frames and propellors together.

Old time recipes call for milk curds (skim and dry) plus lime, mix, add water as necessary and apply. Let fully cure and be careful of not having too much "squeeze out" as a starved joint has little staying power.

Well, I hope this hasn't gone on too long, my 2 cents worth.

MatadorMac
Alcalde, NM

Welcome MatadorMac!

Yes! I just remembered that after asking this question I went digging in the dusty book shelves in search of answers, but forgot I asked this question here and kinda left it in the memory without use .I think we are reading similar books MatadorMac.

The Traditional Bowyer's Bible Vol. 1....starting page 197...Natural Glues and Adhesives

Page 203 is the one with "Curdled milk glue" and the talk about Egyptian furniture making ...it is said this glue was more water resistant than fish glue (thou not as strong) and most importantly>>> doesn't stink when prepared and used. ...interesting what regions was the surviving furniture was found in and the glue joint is very important as well... Egypt's mysteries :farao:

Commercial Casein Glue. Contains dried curd casein, lime, sodium salts and a fungicide. The sodium salts render the casein water soluble - so it can be mixed. The lime waterproofs it again. Commercial casein glue is hard to find but still available. Insects, mice, mold and bacteria will eat casein.
If you wish to make your own dry, storable casein glue, dry and grind curds to powder. To use, stir this casein powder into a solution of water, lime, and lye.

Page 198 >

Water resistant hide glue can be made by adding tannic acid, Formalin, or formaldehyde. These can be added either to the surface to be glues, to the glue surface itself, or can be mixed with the glue. Tannic acid can be extracted from tree barks, especially oak. Old literature reports that hide glue can be waterproofed by adding 40% linseed oil, but my test results showed marginal effects at best. Tung oil works better, possibly because it dries to a harder film much quickly. Even with tung, however, the resulting glue is only mildly water resistant.
Professional glue maker Bob Main believes that formaldehydes which naturally occur in woodsmoke tend to waterproof sinew-backed bows. he feels that sinewed bows cured in the rafters of a smoke-filled lodge would not let down as quickly in damp air

There is also talk about "plant resins"

Injured conifers, especially pines and spruces,"bleed" pitch or rosin, and thou not particularly strong, if prepared corretly the pitch is flexible and waterproof. Pitch is used for hafting(attaching) points and blades, and can also waterproof sinew, rawhide, and gut bindings.

...in the book it explains that to make the resin into glue you would need to soften it and add some ingredients like beeswax and charcoal...black glue joints probably aren't a good thing for nice white bone plating job. :rip:

One fun treat that's also mentioned in this book is "BLOOD GLUE" ...Yummy

Blood thickened with wood dust or lime dries to a moderately strong, water-resistant glue. Untill the mid-40's, pig and cattle blood were used to manufacture plywood

...I think now I'm starting to understand why I "forgot" to get back to this topic

Thank you for mentioning the Bowyers book, I shall have to find a copy and add it to my library.

I deal with adhesives like this and many others constantly during my day job. Several points to make starting with:


[list][*]Amongst the attributes of an adhesive which must be understood in order to use it appropriately is how it reacts with the pieces to be joined i.e. modern polyvinyl acetate adhesives (never to be used for good work) have a joint tensile failure strength of ca. 3000 lbs per inch. Around about the same as a good hide glue, some especially fine fish glues are only a bit less than that figure. BUT, PVA's have large micelles compared to the smaller hide glue proteins. The PVA's fail by pulling the joint materials apart, thus destroying the piece. Hide glues fail across the adhesive themselves when old thus allowing constant repairing.

Also, hide and fish glues penetrate if manipulated to, the surface of the pieces being joined to "key" or to impregnate and strengthen. PVA's can't and don't. Just examples of how complicated getting the right adhesive can be.

Finally, the craft training process and books accurately describing it constantly keep past best practices, knowledge and experience alive and part of the adhesive choosing and using process. Most modern adhesives do not come with such and that is another reason we do so much testing and investigating.

Regards

MatadorMac
Acalde, New Mexico

There are four volumes of The Traditional Bowyer's Bible. I bought mine at Amazon.com as I could not find a place which sold them at a better price. The first volume talks about glues and the testing of such.

I've seen how hide glue acts when drying on a glass surface ... lifting tiny scales of glass as it shrunk...that is some crazy display don't you think?

I've also read that you need to warm the to-be-joined surfaces and apply a layer of very thin hide glue to prepare the surface(having something to do with moisture content of the wood) and only then apply the main batch of glue and continue with the joining of the pieces.

There was a time when I was thinking of formulating my own epoxy, as it turns out there is much fun to be had in that field...have you tried playing with the components yourself MatadorMac?