Walnut soak test

I'd heard on one of the forums that ground English walnut shells presented a particularly serious impaction threat to snakes because they would swell severely if swallowed. However, the package claims that they do not swell and are safe if swallowed occasionally. I placed about 50 pieces of this substrate in a little plastic container and soaked them for about two weeks. After that time, I compared the size of the soaked pieces to the size of a dry piece. I didn't see any swelling. I realize that the liquid in a snake's stomach is not the same as water. My test is not rigorous in any way, but I think this simple test is one piece of evidence that could support ESU's claim that this substrate is safe even if swallowed occasionally.