During acrylic resin processing, the mold must be separated from the surface of the gypsum to prevent liquid resin from penetrating into the gypsum, and water from the gypsum seeping into the acrylic resin. Also, the relatively rough surface of gypsum mould may be penetrated by acrylic denture base resin and adhere to it, to prevent this, a separating medium must be employed. In this study, cold mold seal, tinfoil &olive oil were used as separating medium, and evaluated the effect of these materials on color stability of clear hot cure acrylic resin. Twenty one acrylic resins samples are prepared falling in three main groups (seven samples of each group) according to the separating medium that used and compared the effect this materials on color stability of heat clear acrylic curing by conventional method, the first group used cold mold seal, the second group used tin-foil, and third group used olive oil as separating medium. From the result obtained by t-test shows that there is a statistically no-significant difference (p> 0.05) have been noticed between cold-mold seal, tin- foil, and olive oil samples on color stability of heat cure acrylic resin. It can be concluded that olive oil can be considered as a satisfactory separating medium of clear heat cured acrylic denture base resins, especially because it is easy to get, easy to use and cheap. Also the results have shown that tin foil is still the best separating medium that is used due to easily open the flask during defklasking procedure and removed the samples from stone (most of failure was adhesive ) ,followed by cold mold seal and finally olive oil (most of failure was cohesive ) .