Supporting data for relevant figures within Induced Birefringence in 3D Printing: Concealing Information Optically Within Printed Objects. The deposited files contain the raw data, specifically measurements of thickness and retardation, used to calculate the birefringence values reported in Figures 2,3,4 and 7. Print speed is as defined in the GCODE for each print, given in mm min-1. The extrusion factor is defined as the ratio of material extruded to print length (see manuscript for further details). The layer separation is defined as the programmed PLLA layer height defined in the GCODE script. Thickness values are reported in m and were measured using light microscopy under 10x zoom. Each printed line was cut to produce three small (approximately 3mm in length) samples. Samples were mounted onto card and orientated perpendicular to the lens to find the sample thickness. Retardation measurements were collected by eye in transmission mode using white light with a polarised light petrological microscope, with an inserted Ehringhaus compensator. Samples were taped to a glass microscope slide, and the compensator was rotated until extinction was observed. The value on the compensator was compared to a look up table provided by Zeiss. For each print condition, retardation data was collected, as with the thickness values, from three approximately evenly spaced points along the length of the sample. The birefringence values are calculated by dividing the retardation, given in m, by the thickness, given in m. The standard deviation of the thickness and retardation were used to find the reported error values.