  We present a comprehensive experimental and theoretical study of the kagome
ice Coulomb phase, that explores the fine tuning of critical correlations by
applied field, temperature and crystal orientation. The continuous modification
of algebraic correlations is observed by polarised neutron scattering
experiments and is found to be well described by numerical simulations of an
idealised model. We further clarify the thermodynamics of field tuned Kasteleyn
transitions and demonstrate some dramatic finite size scaling properties that
depend on how topological string defects wind around the system boundaries. We
conclude that kagome ice is a remarkable example of a critical and topological
state in a real system that may be subject to fine experimental control.
