"George Adams" wrote in

Cab-o-Sil. Fumed silica. Available from aircraft and boat supply houses.
Got
mine from an outfit called Spruce Aircraft, IIRC.
Cost is about 12 bucks a gallon, which should be a lifetime supply.


I'm not convinced that fumed silica, as sold for thickening resins, IS the
same as Frog's Fanny. I bought some from West Marine ( not "cab-o-sil"
brand, but fumed silica sold for same market) and it DOES look just like
Frog's Fanny, and DOES dry a fly just like Frog's Fanny.

BUT, that fly does NOT stay dry nearly as well as with Frog's Fanny.
Someone here on ROFF has said that Frog's Fanny (hereafter referred to as FF
is "just a desiccant, not a fly floatant" That is not consistent with
my experience OR the FF label/marketing packaging which clearly promotes
FF's ability to repel water and thus trap air around the fly for nymphing
use.

Indeed, a desiccant absorbs water by definition and any left on the fly (
that white look) would quickly attract water and sink the fly. That is
exactly what I find happens with fumed silica. But NOT what I find with FF,
with it I seldom have a sinking fly until the next fish slimes it.

I carried two bottles this summer for over a month, one "real" FF, the other
a FF bottle filled with fumed silica. I make no claims of good science but
I did try to be random in which I used, honest in my evaluation of the
results. I ended up putting the fumed silica in my shop with the
fiberglass supplies and I now carry nothing but store bought FF. BTW, the
difference between the two is least obvious with CDC where "desiccant" is
the real need, but far more so with other types of materials that need to
not only be dry but need help repelling water to float for long. I'm cheap
and would love to avoid the high price of FF which I also love, but fumed
silica, as I tried it, is not the answer.

YMMV and all other disclaimers apply and, again, "Cab-O-Sil" is not the
brand of fumed silica I tried.