Have any of you hybrid Sheller/furniture refinishers ever tried Trisodium
phosphate (AKA TSP) for removing all types of finishes including varnish?  It
is available as a powder at the paint store or Home depot. I have used it
disolved (saturate solution) in hot water  to just wash away the finish on
furniture, but have never tried it on a shell. Might be worth a try on the
varnished shells . Try it hot and just soak the varnish off. Wear rubber
gloves.

Jim Emmett in Colorful Colorado