The focus of this study is to analyse the effect of air pressure variations in the sandblasting process on the surface roughness of 6061-T6 aluminium. Sandblasting is a method of cleaning and modifying surfaces by spraying high-pressure abrasive particles to remove contaminants and improve the adhesion of the coating. 6061-T6 aluminium was chosen because it has a combination of high strength, good corrosion resistance, and stable mechanical properties. The variations of air pressure applied in this study include 2.5 bar, 3 bar, 3.5 bar, 4 bar and 4.5 bar with silica sand measuring 60 mesh as an abrasive medium. Other parameters controlled include a nozzle distance of 10 cm, a spraying angle of 90°, and a spraying time of 30 seconds. Surface roughness is measured using a Surface Roughness Tester with Ra, Rt, and Rmax parameters, while material thickness is measured using a micrometre. The results showed that the increase in air pressure significantly increased the surface roughness of 6061-T6 aluminium. This is due to the greater impact energy of abrasive particles at high pressure, thus creating deeper microdeformations. These findings are expected to serve as a reference in sandblasting parameter optimisation for industrial applications that require precise surface quality control.