  Stars observed in the field of an open cluster are ideal for a controlled
test of chemical tagging. Using chemical tagging, one should identify the
cluster members, i.e., those stars of similar chemical composition, if their
composition is indeed different from that of all the non-member stars of the
field. Moreover, the abundance-based membership can be checked against
membership based on radial velocities and proper motions. Here, I report
preliminary results of such an experiment using data from the Gaia-ESO Survey.
Although the three membership criteria usually agree, a few interesting
examples of discrepant membership classification have been found. In addition,
the mean composition of each open cluster was compared to a sample of 1600
Gaia-ESO field stars. Some cases of field stars with abundances matching those
of the open clusters were identified. This experiment suggests that open
clusters do not necessarily have unique abundance patterns that set them apart
from all other clusters.
