A Question on Glue

[Vindex]

Those of you who use or make organic glue of the period - animal parts and plant - which one is the most effective for holding laminated wood together; and which is the most water resistant?

Is there one which is water proof? And by that I mean can survive being immersed in water and still maintain it's gluing properties.

I am becoming less and less convinced by laminated wood for a Roman saddle; for although lamination provides strength, a saddle clearly does not have the same area as, say , a shield and I wonder just how strong laminated wood would be for a saddle tree (or frame).

I've seen quite a few broken, laminated trees (including a Connolly saddle).

Thank you in advance.

[XorX]

The most effective ones are glue made of rabbit skin or the one used for composite bows, which is made of sturgeon bladders.
They both are not water resistant for themselves, but can be made so by mixing a small percentage of alum to it.
In composite bows, the covering makes the construction water resistant

[MacG]

There are other ways of making glue. In ancient times one used to boil horse-hoofs or those from cows till they became more or less liquid. There are other mixtures like natural resins and grounded horns/bones. Those are partial water resistant.

I have somewhere old recipes for the making of organic glues. If necessary, I can look them up.

[Musivarius]

Interesting, I never realised rabbit skin glue can be made waterproof. We use in in mosaics if you need to lift one from it's base to replace it. Surgical gauze is glued over the top and then when the mosaic is reset you use hot water and a scrubbing brush to take off the gauze.

Thanks for posting that. How do you work out how much alum you need?

[XorX]

Most sources say that about 10% of alum (according to the DRY amount of glue before adding water)makes the glue waterresistant. It is stirred in the warm liquid lime.
Also adding of lime casein has the same effect. But i never worked with that and have no experience.
Lime casein for itself also can be used as glue, but there seems to be no archaeological evidence for that