  The region of permanent densification beneath a Berkovich indentation imprint
in silica glass is investigated using a novel chemical dissolution technique.
The use of the similitude regime in sharp indentation testing allows one to
record reliable data with a good spatial resolution that makes it possible to
deal with low loads (typically below 10 mN) and crack-free imprints. The
densified zone dissolves much quicker than the non densified regions. The
analysis of the results, along the vertical axis, indicates that the
densification zone is rather homogeneous with a steep transition to the non
densified zone. The size of the densification zone, with respect to the initial
free surface, is estimated to be around 1.9 the maximum penetration depth of
the instrumented indentation test. These findings are compared with former
experimental data and critically compared with the results of numerical
simulations from selected constitutive equations and other numerical techniques
from the literature. These comparisons highlight some advantages and
disadvantages of existing modelings and thus call for further advanced progress
on that matter. They nevertheless favor mostly the contribution of the
densification process with respect to the plastic flow (volume conservative
process) in creating a permanent imprint.
