Metal cleaning has the potential to make or break heat treat processes. However, many heat treat companies are struggling with common cleaning challenges, including residual contaminations leading to insufficient hardening/nitriding/brazing results; surface stains on the finished products; inconsistent cleaning process as well as high cleaning costs due to high consumption of cleaning agent. In addition, burned oil can cause increased maintenance costs of the equipment and contaminate the facilities. The decision for a cleaning agent or sustainable cleaning technology has become more and more important under the aspect of current legislative efforts by the Environmental Protection Agency (EPA) in the US. This paper discusses the underlying causes behind these challenges and explains key factors fundamental to ensuring high-quality metal cleaning in terms of consistency, reliability and sustainability. Furthermore, it will introduce legally compliant, state-of-the-art cleaning capabilities such as closed vacuum cleaning technology with solvent, also known as airless system, the combined (two-step) process of solvent and water in one machine; as well as a simple one-process step with two solvent based media. The theoretical principles will be further illustrated through a joint study with HEMO GmbH (HEMO), a manufacturer of cleaning machines, on cleaning trials based on different metals and contaminations.