 There's a reason why hospitals and public spaces are rife with metallic surfaces and it isn't because of their sleek look. Metals like stainless steel, silver, and copper have the capacity to kill bacteria and other microorganisms, reducing the spread of infections through doorknobs and other high-touch surfaces. But understanding the microbial killing efficiency of metallic surfaces is tricky business. Though some standard testing protocols do exist, not all of them mimic real-world conditions. In keeping with the goals of the United Nations' 2030 Agenda, an interdisciplinary team of researchers at KTH and Ames, within the framework of the IHMEC Central Baltic Project on Indoor Hygiene, are dedicated to promoting good health and well-being by focusing on the materials and services that we share with microbes every day. That's important because bacteria and the substances they produce can greatly alter different surfaces. The research team at Ames has developed a method that provides a new, more realistic and reproducible approach to determining the antimicrobial efficiency of surfaces frequently in use. This is based on recreating the effects of time, weather, and the human element on materials. These include fluctuations in humidity that indoor spaces experience every day and even the effects of human sweat on the properties of copper surfaces. Researchers simulated fingerprint contact by adding bacteria onto corroded surfaces with and without droplets of artificial sweat. The droplets formed a thin, watery layer within a few minutes and evaporated much faster than layers formed using less realistic test methods. This so-called quasi-dry approach revealed rapidly reduced viability of E. coli bacteria within sweat droplets, a killing effect that could be traced to copper surface characteristics and the copper ions, and their increasing concentration with evaporation. Further experiments demonstrated that differences in the corrosion products formed by humidity and sweat alter the physical properties of high-touch copper surfaces. For example, corroded surfaces showed a higher surface roughness, which can make surfaces more lethal by increasing the number of footholds bacteria can latch onto. As new knowledge often leads to new questions, more work is needed to understand how these chemical and physical alterations might modify the antimicrobial properties of high-touch surfaces. Ultimately, the new methodology enables researchers to incorporate important real-world conditions into experiments. Equipped with a more rigorous and realistic testing approach, researchers could begin to find newer and better ways to keep surfaces free of harmful pathogens, thereby hindering the spread of infections and protecting the health of people and our society.