true - but it's probably more like the binding agents that degrade. the stuff that confers the UV protection, e.g. titanium dioxide or zinc oxide - those oxides are stable. i was just hoping to saturate the fabric with the stuff but yeah, i wonder how long before that stuff washes off in the rain.



You'll probably notice that sunscreen has an expiration-date. That date is for when it's
stored in normal conditions (like in a cupboard), in the original container. When it's used,
outside in the sun, the stuff might become useless in a few hours or a few days.

--
croy