Here is a nice example of the Subtraction tool of the corporate innovation method, S.I.T.. Imagine painting a picture without the paint. From PSFK:
From metal to billboards, Portuguese artist Alexandre Farto aka Vhils is regarded for his work across a variety of mediums. However, his “Scratching the Surface” style (which we first noticed here) is particularly remarkable. Using decrepit city walls as his canvas, the artist carved faces from the concrete, unmasking the beauty inherent to even the most neglected spaces. The pictures below are taken from Moscow, London, and all over Italy.
To use Subtraction, start by listing the components of the situation, product, service, process, etc. (The method works with just about anything that can be conceptualized into components). In this case, the innovator (artist) would create a list something like this: