Aphrons are dispersed micron-sized bubbles in a liquid.Thesefine bubbles are produced by using a very high shear rate into of a surfactant solution. Colloidal gas aphrons (CGAs) relatively stable dispersion but finally they gradually losing their stability and they separate into a clear liquid phase and a foamy phase. Characterization of aphrons is necessary for getting better knowledge on their performance. Two most important features of CGAs are their micron sizes and relative high stability. These features resulted in numerous applications for aphrons. Study on the effect of geometric specifications of Aphron Generator on CGA stability is very limited. In this thesis, the effect of different baffle positions and various diameters of rotating disk of Aphron generator on stability of generated Aphron bubbles have been investigated. Also, a comparison was made between various surfactants and finally the Nonyl Phenol Ethoxylate-20 (a local product, nonionic surfactant) was introduced. Changing in geometric specifications of aphron generator reveal some unpublished results on aphrons behavior. This work is an attempt to show that the macroscopic CGAs behavior, due to geometric specifications of Aphron generator, can be realized from drainage curve. The results showed that: a) Rotating disc diameter and baffle position effect on stability and the effective gas volume fraction but these effects decrease with increasing the stirring time and surfactant concentration. b)Increasing the surfactant concentration can always increase the stability of Aphrons at the second phase of drainage curve. c) Under any circumstances, the increase in the surfactant concentration leads to an increase in the gas volume fraction in CGA. Key words CGA, stability, NPE-20, curve drainage, geometric specifications of Aphron Generator, disc diameter, baffle position