After the death of prisoners in 19th century Poland, prison staff removed their tattoos to preserve the relationship between prisoners. Recently, photographer Katarzyna Mirczak documented the tattoo samples found in the Department of Forensic Medicine at Jagiellonian University in Krakow, Poland, according to the Huffington Post.

According to the article:

It was forbidden for Polish prisoners to tattoo themselves, yet they’d use clips, pins, wires, razor blades and pieces of glass to puncture their skin and add any number of substances to make the designs permanent, according to a Mirczak press release. Colors were formed using powdered charcoal, burned rubber, cork, pencil refills, ink, watercolor and crayons. Those pigments would then be mixed with water, urine, soap, cream or fat.

To read more and view Mirczak’s photography click here (some images may be NSFW).