Mesured a drying bow day by day and had surprised.
The last layer layed on at 3. Jan. and after 2 weeks put the bow in the room where the temperature is 20C and the Rh is about 45-50%. So it is ideal for a hornbow to drying out totally.
After a week or so the weight loose was about 0.5g/day, than a few days later start to go back to 1g/day and now the last few days (after 25days) something happened and the weight loose fasten up! :shock:
Today was 1.6g/day!
Any ideas what is this?
My idea is, more hidrogen bond borning in the struture and press out the water molecules.
The room is not warmer than usual and the outside Rh is 76%.
So the change could happened just in the sinew glue layer.
Will mesure the weight drop in the next weeks too....
If I'm right after the polimerisation, this weight drop will slow down drastically.
Adam Karpowicz
Zoltan - I suspect the humidity dropped around the bow for some reason. It could be the weather turned cold and your room became drier inside, even though it was at 50%RH before. It could be the air around the bow became warmer and it dried out faster - for example a sunny day with the sun warming the bow thought the window? I found the humidity can vary as much as 10% in the same room.
Bear in mind the moiture content in organics is high. At mid range humidity it is in the order of 10-15%. A bow 500 grams weight will have 50 to 75 grams of water in it. So 1-2 gram difference is not much and small change can show on the scale easily. One needs a very accurate RH meter and controlled environment to test these things.
Hydrogen bonding can occur in a dried glue, but only when the molecules are either more mobile (usually at high water content) or when they get closer to each other as the glue dries further. I suggest to stop using the word "polymerization", which is a wrong term here.
Adam
ketene
I've followed the loss in weight of 2 horn bow I've made in december.
I stuck them in the dining room where the temperature is about 19-20 ?C.
Further to a remark of my wife who does not find these bows very beautifull, I took them up in the second floor where the temperature is no more than of 10 ?C.
The weight was not the same one day later.
Hydrogen bonding can occur in a dried glue, but only when the molecules are either more mobile (usually at high water content) or when they get closer to each other as the glue dries further. I suggest to stop using the word "polymerization", which is a wrong term here.
I'm agree with you. It's not a polymerization ? If you put old pieces of backing sinew ( an piece of broken hornbow ) in water, you have 3 days later fibers sinews just like they was 2 years ago when you made the bow. By polymerization it will be impossible to obtain fibers sinews.
It's just by hydrogen bonding that we are ablle to obtain a backing. This process looks like more a cristalisation. By the hydrogen bonding there is a strong rearrangement of macromolecules.
I've just a question without answer. How can move macromolecule when water decrease.
Excuse me my english is bad.
alex27
Hydrogen bonding is maybe a confusing term to explain the processes going on when the sinew is drying.
Hydrogen bonding is more of an INTERACTION between molecules than it is a BONDING, like in poymerization. It occurs between polar molecules where a bound Hydrogen atom forms a 'bond' with bound Nitrogen or Oxygen.
The glue is basically protein, and the fibers are as well. There will be sufficient electronegative atoms to form hydrogen bonds.
Crystallization is also not right and the macromolecules don't have to move.
