that the fine grit that was on my face was crystallized salt from sweating? I noticed it after a "sweaty" 40 mile ride. It reminded me of the very fine play sand in my son and daughters sand box. Maybe it was road grit or something else? It was very light in color and I have never noticed it before.
Trek road bike, Cannondale(ancient) just purchased a Gary Fisher HKEK "05"
I just read an article in Outside magazine stating that some people sweat out more salt than others. This seems to be the case with you. They suggested drinking a sports drink (like Gator Aid) to replenish the body rather than just water. Our bodies run on a sodium driven system.
Unless you've been riding through a dust storm, it's salt.
You have given me good advise on other questions.
On this issue of salt loss please let me know: I did 100 miles/day in 100 degree and high humidity. I consumed 9 liters of water, ice tea and two sandwiches (Subway).
Did I deprive my system of salt? The last leg of the 100 miles seemed much harder and I had to slow down 10%.
I have done this same trip before, many times, in cooler weather without that problem.
In other words: Is it salt or just overheating?