Scientific article in the Journal of Contaminant Hydrology claims “Sepia ink is an organic pigment consisted on a suspension of eumelanin, and that has several advantages for its use as a promising material for introducing frugal innovation.

… in the fields of public health and environmental research: very low cost, non-toxic, spherical shape, moderate polydispersivity, size near large viruses, non-anomalous electrokinetic behavior, low retention in the soil, and high stability…

We concluded that sepia ink is a suitable cheap surrogate for exploring transport of pathogenic viruses, bacteria and particulate contaminants in groundwater, and could be used for developing frugal-innovation related with the assessment of soil and aquifer filtration function, and monitoring of water filtration systems in low-income regions.

Read the article if you are scientific minded or even if not, just go absorb the essential points they make at this link here.