Letters of Ravensbruck concentration camp written with "invisible ink" found in Poland

Some letters that Polish women prisoners in Germany's Ravensbruck concentration camp during World War II wrote using urine as "invisible ink" to their families have recently been handed over to Lublin Museum, the Polish TVN 24 portal reported on Wednesday.

The women prisoners were objects to many inhuman experiments and had full consciousness they would most probably die. Due to the fact that their correspondence was censored, they used their urine as invisible ink to let their families know the secret information about their fate and the situation within the camp. They used thin wooden sticks to write on the internal side of envelopes or between the lines of "regular" letter, written with a pencil. The families would iron the letters which made the secret texts visible.

It all began with two Lublin girls, Nina Iwanska and Krystyna Czyz. Krystyna made a remark in a letter to her brother, reminding him about a book they used to read. The main protagonist of the book wrote a letter, the first lines of which included secret information. Krystyna's brother understood the hint and was able to read her message. It was also her family who gave 27 letters written between years 1943-1944 to the Lublin Museum, according to the report.

The women in Ravensbruck were victims of inhuman medical experiments. The letters also include information about the camp's functioning, labor, and death sentences.

Ravensbruck was a German concentration camp for women located in northern Germany. It was opened in May 1939. Between 1939 and 1945, some 130,000 to 132,000 female prisoners passed through the camp, including around 40,000 Polish and 26,000 Jewish. Endit