Sprayer provides a fine, uniform spray ideally adjusted for the development of chromatographic patterns. Spray pattern is adjustable by varying the coverage of the vent hole with the user's thumb. Sprayer is used with low pressure air (5/PSI) or rubber pressure bulb. Sprayer consists of an atomizer top attached to the reservoir with a Rodaviss 24/40 joint. This design provides for a positive, grease-free seal between the atomizer and reservoir and eliminates the glass hooks used on other sprayers. Complete sprayer consists of the atomizer top, Erlenmeyer shaped reservoir, CG-182-03 open-top screw cap and CG-305-26 #212 Viton O-ring.