what apply to rawhide backing?

You have:
a) rawhibe backed wooden bow
b) sinew backed bow covered with rawhide.
c) rawhide wrappings to help splices
d) something else

Sorry, i have hornbow and after sinew backing i applyed rawhide backing!

Now rawhide and glue is dry, and im worry about bending! I thing then rawhide is not too flexible, what do you thing about it. Must i do some smoothing procedure or not? And if yes, which way?

I think rawhide over sinew was a very bad choice.

Most historic bows have only a very thin layer of birchbark or silk or layers of lacquer for waterproofing, not a heavy backing of rawhide on top of sinew.

Both rawhide and leather were also used. You can use varnish over rawhide . A finish like Tru-oil also works very well. Wax is a good maintenance coat.
Rawhide is flexible on its own.

The main purpose of leather or birch bark layers over sinew was to moisture-proof it. Rawhide will not do that and, unless it is the thinnest parchment grade, it will just add weight to the limbs. However, if it is ultra thin it could serve as a base for varnish. That was how leather was used. Tanned hide, like rawhide, was not particularly water resistant but it did provide a good surface for paint and varnish and it was less prone to rot and more flexible while being applied.

thanks :) But which varnish you mean? I readed about shellac on atarn.
Now for me is available polyuretane varnish for wood. Its not traditional, but i already have it. Question is about his mechanical properties

There are several varnishes that were historically used.
Plant resin based varnishes are explained in detail in Adam Karpowicz's book. Books on old violin making technique are useful too.
Shellac is a good period varnish though it probably was not used until efficient alcohol distillation was common.
Chinese lacquer was used in the east. It is called urushi in Japanese. It is made from the the sap of trees of the genus Rhus and is poisonous when raw.

The basic premise, which would apply to modern varnishes too, is that you put on thin coats. Thinner is more flexible. It takes more time but the result is better.

Modern lacquers, epoxy and other, have similar properties, but each one should be evaluated by testing on a thin flexible lath that can be bent extensively to see if there is cracking.

Thank so much. I can ask violin maker, i know he use resin from cherry tree, for making varnich. I didnt know that it is usuable :)

Cherry gum is not a varnish - it is a water-base paint binder and readily soluble in water, not water resistant. Whatever you use, before you paint the bow, it is important to shoot the bow for a while to make sure the cover sticks and repair where needed.

BTW, is there a concrete evidence of urushi use on bows? I have some doubts, because the curing process for this varnish requires very high humidity - not quite compatible with horn bows. As far as I know there are modern urushi-like, modified varnishes that cure at lower RH and probably sold as urushi.

Adam

Violin makers know a lot about varnishes. Subtle differences can change the resonance of the wood. The old man I knew had been researching and testing for years.

I have used modern Polyurethane finish on both rawhide and on sinew, works fine. Polyurethane dries to a hard finish, but is still flexible. Markus.

So now my bow is broked, during I heave on a string :( Before rawhide i shooted from this and it was great!!! Broked place is direct in interface between handle and arm, there was littlebit weaker place i thing, but it worked good.

possible reason, just my opinion:
1)After rawhide remained possible moisture
2)During the some days inactivity was bow returned in the original c shape! I think that I should use teplik jig, as when opening bow firstime!

broken place is on foto, left side bandaged place...

For Adam.
Sorry I missed your comment. There are several Han dynasty bows which have composite construction and lacquer varnishes that have been excavated under controlled conditions. It is possible that lacquering bows started in the Chu state on laminated bamboo bows and was then applied to composite bows. The Chu state was on the Yangtse River and had a large naval establishment. It is likely that using lacquer on bows was originally developed to protect the bamboo and glue from high humidity.

Jaap Koppedrayer successfully made wood/horn/sinew bows with lacquer (urushi) as the varnish. I saw them shot in Utah at a measured 10% humidity without visible cracking in the lacquer surface. The same bow had been used a few weeks before in Georgia at a measured 90% humidity. I expect that long exposure to the low humidity conditions would have been bad for the lacquer based on what I have read.

Yes, I was aware of the ancient use of urushi, but I was hoping for a positive id on an old bow (unless this is what you meant in your post - in that case I'd appreciate the references).

Adam

I found references to bows with lacquer coatings in several articles in the journal, Wenwu. There were some in other archaeological books, all in Chinese, but I made notes so I will see if I can find them. It was mostly Han dynasty material. There may have been other reports on later excavations.

In general, there were other reports on other weapons with shafts wrapped in various materials and covered in lacquer.