  We have reinvestigated the collision of gluonic bubbles in a SU(2) model of
QCD which was studied by Johnson, Choi and Kisslinger in the context of the
instanton-inspired model of QCD phase transition bubbles with plane wave
approximation. We discuss treacherous points of the instanton-inspired model
that cause the violation of causality due to the presence of imaginary gluon
fields. By constructing a new slightly modified Lorentzian model where we have
three independent real gluon fields, we reanalyzed the process of bubble
collisions. Our numerical results show some indication of forming a bubble wall
in colliding region.
