Walking barefoot makes skin on the soles very hard. Indigenous tribes that have no boots are walking barefoot even on the sharp rocks.
But after my leg was slightly slit by the seaweed, I wonder if it is possible to do the same with the skin on the other parts of the body. If so, how to achieve it? Generating so much friction as to soles when walking would be very problematic.
Scar Tissue
You would need to strike a balance between doing enough damage to build callouses, and not doing so much damage that you cut yourself (and build scar tissue). Scar tissue is weaker than regular skin, and can take weeks to a couple months to fully heal, and get strong again.
My somewhat related experiences
In rock climbing, there's a technique called "hand jamming", where you use your hands as wedges to climb a crack system. I have met old climbers out West (Wyoming and California) with crazy thick callouses on the back of their hands. So, I'd say, yes, it apparently is possible to callous up skin on different parts of your body (in this case, the backs of your hands).
Whenever I try and climb hard hand-cracks without athletic tape, I just scrape myself up, and get scars on my hands that take a while to fully go away. As a weekend warrior, I don't think I could duplicate the lifetime of climbing it would take to slowly build those calluses. I could probably devise a skin-training regiment I could do daily, or every other day, to toughen my skin up. But assuming my goal is to be a better climber, I have better luck just taping up, and working on my technique. (honestly, I think that's a better application of my limited training time).
My $0.02
Edit:
I should say, one of the climbers I met was an old guide, who had thicker calluses on the backs of his hands than most people have on their feet. He also had long, grey dreadlocks. It looked weird, but kinda cool.
Not really, no. What strengthens skin is damaging it, either by rubbing or by cutting/scuffing, so you end up with either thicker/rougher tissue or even scar tissue.
I would imagine running through long sharp grass every day could do this quite well but it would not be fun.
I haven't tried it yet, but I hear that if you rub hard with coarse sea salt over the skin on the desired area that it should toughen it up. The coarse salt will cut into the skin, damaging and scaring the tissue. You will bleed but the salt should act as a coagulant. I don't see the salt cutting too deep for anyone to worry much, keep it away from your eyes is a thought.
Yes and no depends on how high your tolerance for pain is?
If it's low no.
If yes then exposing it to weak acids can toughen it to a point but you will still get hurt. This effect can also be duplicated using intense heat.
The only reason I know this is because some European nations use to do it as a way of toughening their skin so that they could survive moving around. Used mainly by pesents to survive bandit attacks without buying expensive armor.
