Up until the late 19th century mercury was used in the felting process. It was discovered that mercury attacks the nervous system and causes poisoning, hallucinations, and psychotic states. Hence the term mad as a hatter.
The Mad as a hatter collection consists of 9 felt caps and hats, and there are four different principles of forming shapes. The colour scale calm, ‘wintery’, in a uniform intensity, from brownish to grey tones, combining the two sides of the material.