Use a lint-free cloth (or coffee filter) with either isopropyl alcohol or ArctiClean Thermal Material Remover to thoroughly clean the thermal paste residue from both the CPU and GPU arms of the heat sink.

Once the heat sink surfaces are completely clean, use a fresh lint-free cloth or coffee filter to apply a drop of ArctiClean Thermal Surface Purifier to remove any oils and prepare the copper heat sink surfaces.

Do not touch the copper surface with your bare fingers, or allow any dust or debris to get on it. Even a fingerprint can be a major obstacle to thermal transfer. If you touch it accidentally, re-clean it and re-apply the surface purifier.

Allow the heat sink to dry completely while you continue working.