1. A method to detect the presence of a substance on a test swipe, comprising: capturing a background image of the test swipe; applying one or more test chemicals to a test swipe; adjusting the temperature of the test swipe to a predetermined temperature range; capturing an in-situ image of the test swipe after the application of chemical at the predetermined temperature range; subtracting the background image from the in-situ image; generating a difference value from the two images; and searching a known database to identify the substance.