William henry talbot’s photographic system involved placing the negative against a treated surface that was then exposed to chemically / sunlight heat /chemicals motion / heat

The answer is: “William Henry Talbot’s photographic system involved placing the negative against a chemically treated surface that was then exposed to sunlight heat.
He devised several ways of chemically stabilizing the results to make them sufficiently insensitive to exposure that the sunlight could be used to print the negative.