Originally posted by Dark Nemesis
What is tannic acid?
Its not so much the by product of the process as it is what makes the process. The tannic acid or tannin comes from the bark of a certain oak, cant remember which, which is soaked in solution. The raw hide is then immersed in the solution for a predetermined amount of time. When it comes back out the rawhide is chemically converted to leather! Its thouroughly rinsed, this is the key, and dried. The amount of tanin left in the leather is what makes it corrode metals. The quality of the leather has a lot to do with the amount of tannin left in it, the lower qualities are more likely to have a bit left in, the higher qualities are less likely. I had some really cheap stuff a few years back that I soaked in warm water for a few hours.....the water looked like tea!
Now as for leathers, you have oak tanned, therefore tannin cured, then there is vegitable tanned which doesnt have as much in the way of acids in the tanning fluid and is rinsed better as long as the quality is there. Others are oil tanned, there is a fine line here watch out for these, some are chrome tanned and then heavily oiled. Chrome tanning uses chromium salts and they do remain in the leather and will corrode metal very quickly.
Now as for storage of blades in leather, I have 1095 steel blades that have been stored untreated in my sheaths for months with no adverse effects and I live in a humid area. Now the same leather will put a patina on brass and or copper. Dunno. I dont tend to worry about my leatherwork because I spend way too much on leather and I hand pick it as well, so I know what I am getting and what I am selling. When you do your own personal work I suggest you spend the extra money and get #1 grade leather, its worth it.
Its good to know your materials, like what kydex does to beadblast blades....
