Isopropanol is also know as Isopropyl Alcohol and IPA (not the bitter) is a quickly evaporating Alcohol based chemical that cuts through Thermal Paste and residue allowing you to clean your CPU/GPU die and surrounding areas before applying new thermal paste.
Isopropanol works fantastically with Arctic Silver products and allows you to shine the core for perfect heat transference with the thermal compound of your choice. Instructions For Use:Pour some of the Isopropanol into a container (Egg cup or similar) during the cleaning process you may accidently put your dirty Cloth or cotton bud back into the liquid, ideally you do not want to contaminate a whole bottle which is why you remove a small amount for each cleaning.
Thermal Material and excess Isopropanol. Reapply the isopropanol with a clean Ear Bud and repeat until all thermal material has been removed. Please take care when cleaning GPU cores as they are mounted on the graphics card generally surrounded by resistors, you must ensure you remove all traces of the Thermal Material.