I am sure you've seen several Robert Oster Signature Inks reviews... This one is more a drawing review.
Khaki is a lovely color, and it washes beautifully... The line work was done with G nib (dip pen) and the paper is Bristol (Vellum finish).
The ink is not waterproof, but is saturated enough to provide great shading. Dries quickly and overall is very easy to work with.
The author of the drawing below is my artist-in-residence.
DISCLAIMER: The portrait is not representative of Robert Oster's good looks... We haven't met the man. ................ (yet!!)