I have a long-held fascination with making colour-changing artworks using polarizer sheets.
Polarizer sheets are thin, transparent plastic sheets, not unlike acetate sheets. However, polarizer sheets have a specific property: they consist a myriad of microscopic size slits, uniform in size, all aligned in the same direction. When light hits the polarizer, only those components of the electromagnetic light waves which are aligned with the orientation of the slits are able to pass. This change in light’s structure is not normally noticeable to the naked eye, nevertheless it makes polarized light inherently sensitive to direction. If this kind of light travels through transparent plastics that have been stretched, bent or otherwise deformed, then the points with different stress levels will produce different colours after passing through the polarizers. This phenomenon is known as optical birefringence.
One of the many important practical applications of polarization is that it can be used to detect structural defects or stresses in transparent materials. Placing a transparent material between two polarizing sheets reveals these physical stresses. Stress in a material is often created by added pressure which alters the thickness of the material. This alteration of thickness can be very slight. In my art practice I deliberately create transparent materials with alterations in thickness in order to observe the light phenomena produced by the polarized sheets when this “defective” transparent material is sandwiched between the two polarized sheets.