The purpose of this work was to prepare microemulsions containing tea tree oil, a potential
natural anti-bacterial activity. The pseudo-ternary phase diagram was constructed to identify
microemulsion region. Tea tree oil, water, tween-80 and PEG-400 were used as oily ingredient, aqueous
phase, surfactant, and co-surfactant, respectively. Different ratios of surfactant to co-surfactant (1:1, 2:1
and 3:1) were designed. The results indicate that a mass ratio 3:1 had higher microemulsion region than
other ratio. The microemulsion obtained from this pseudo-ternary phase diagram were then sampling for
5 different ratios to evaluate the microemulsion characteristics. It was found that formulation
microemulsions properties were of an optically transparent, homogeneous and low viscous with an
average droplet diameter of in the range of 47-101 nm with a PDI