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, local media reports said.
According to Polish TVN 24 portal, the women prisoners were abjected to many inhuman experiments and were fully conscious that they would most probably die. Due to the fact that their correspondence was censored, they used 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, Xinhua news agency reported.
It all began with two Lublin girls, Nina Iwanska and Krystyna Czyz. Krystyna hinted about using the method to write letters to her family members in a letter to her brother. According to the report, it was also her family who gave 27 letters written between years 1943-1944 to the Lublin Museum.
The women in Ravensbruck were victims of inhuman medical experiments. The letters also include information about the camp's functioning, labour 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.