Rather than nail polish, for long-term storage, the US
National Park Service recommends clear Acryloid B-72
--- diluted 25% with acetone --- plus india ink, and
white Acryloid B-72 laquer for background as
necessary. More-diluted Acryloid B-72 is recommended
by conservators as a consolidant or glue.

On specific use and dilutions, check out this 1993
Conserv-O-Gram from NPS
http://www.cr.nps.gov/museum/publications/conserveogram/01-04.pdf

and this message on actual use and storage from the
Conservation DistList, which mentions using a 30%
dilution instead:
http://palimpsest.stanford.edu/byform/mailing-lists/cdl/2002/0913.html

Make sure you have plenty of ventilation when using
this stuff.

Gwyn Alcock
Statistical Research, Inc.
Redlands, California

Anita Cohen-Williams <[log in to unmask]>
wrote:
What we do (and don't tell the museum folks this, they
tend to go
ballistic) is to put down a small layer of white out,
let is dry, and then
write on that. Once the ink dries, put on a coat of
clear nail polish on it.

This is how we mark all our artifacts, including the
metal.

Anita Cohen-Williams
Search Engine Optimizer/Guru