birch bark how to work with?

Andrew Hall has recently posted about his Omnogov bow. He used birch bark to back it and did a marvelous job, I'm sure he can help.

I can only speak from the Korean experience. In a nutshell, the Korean bowyers soak the birch bark in sea water for a year and then boil it for several minutes before use.


T

And then most of his bows visible vith crackers in birch bark :cry: same is visible in modern variation vith birch bark cover.This problem is trouble for me too. In old chinese and turkish bows in pictures dont see this problem (maybe picture failure ?)What is directly science name of this type birch ?

I think there are special problems with Korean bows because they are so recurved.

With Chinese bows, which are nearly straight when unstrung, there is relatively little problem with applying birch bark. Problems arise with air bubbles under the glue, so the bark must be attached to the surface with both the sinew surface and the birch bark very warm. Then it must be immediately pressed down with a hot clothes iron.

Yang Wentong maintained that for the best results, there should be a covering of saliva over the glue just before the bark is pressed onto the sinew surface. Enzymes in saliva may have a part to play.

The saliva helps to break down the surface tension between the bark and the glue. I remember in the Chengtu article the bark was licked before applying to the bow. This should help a little, since tha bark is naturally water-repellent.

The bark is difficult. For best results the surface of sinew must be exceptionally smooth to give better contact with the bark.

I am not sure about the Korean methods. I have not found the soaking and boiling to be useful. Maybe the soaking in salty water helped to preserve the bark wet without spoilage? The wet bark can be divided later into layers much easier. It is true the boiling softens the bark, which becomes stretchy and soft like rubber, but the places around lenticels wrinkle up and the softness disappears instantly upon cooling. Maybe the boiling made the bark more receptive to glue, since some of the "greasiness" would be removed in the process? More experimentation is clearly needed.

Adam

I have made 3 birch bark backings and every time I took the bark from tree and put in on with hide glue. Both ways, inside out or inside in.

What about the direction of the grain of the bark? I have a Chinese bow where the bark is diagonal on the limb (about 30 degrees from perpendicular to the limb) , long on the siyahs and perpendicular on the grip. Koreans put the grain parallel to the limb.

All Tut's bows which had birch bark are perpendicular to the limb. Other Chinese bows, the bark is like a chevron meeting at the centerline of the back but not covering the belly.

If wrapping it may be better perpendicular but if on piece maybe the grain should go with the limb.

Mechanically the direction of bark does not matter. Longer strips are less work for the bowyer, so these are best put on the limbs, while the grip can be covered in scraps. At the same time bark can not be bent over the ridge of kasan (or of the knee), so two parallel pieces are the only solution there.

Most of the time the strips cut from a tree are diagonal to avoid knots, blemishes etc, especially when cut from smaller diameter trees.

Adam

but the places around lenticels wrinkle up

Adam, what are lenticels?

It should be lenticells, sorry. These are the elongated dots or lines on the bark. Bark from younger trees has smaller lenticells.

Adam

"Mechanically the direction of bark does not matter"
Well it cracks easier following the grain.
"Bark from younger trees has smaller lenticells. "
What about higher up on old tree?

Maybe you can wrote more for us about birch bark , Redhorse. I trust more man whu live in north (sveden, finland, norvay, russia...) People in all this countries lon time working vith natural materials - especilay like birch bark.From this bark was shoese,bowls,cups etc.

Redhorse, I saw bows with the bark grain along the limbs as well and did not see any more cracks there. I use diagonal bark on my bows. Bark is very stretchy and can accomodate the bending very well, as long as the adhesion to sinew is good. If the adhesion is poor, the bark cracks.

Adam

hi guys,

thanks a lot four your answers and contributions. if i understand well the essence of all this is that you can boil it soak and it put/glue it anywhichway on the bow.

well, the bark pieces i have are about 30x40cm big and about 1,5mm thick.

-->> the question still remains which bark layer do i use and how do i separate the layers to get the right one?

thanx, stefan