For best results, use in a dimly lit room against a dark background. This handheld portable model requires 4 AA batteries (not included). Short wave lamp This short wave lamp will clearly show the phosphor and phosphor afterglow on GB stamps up to 1992. For best results, use the short wave lamp in a dark room; the darker the room, the better. To see the different colored phosphors on the 1960 Wildings issue, observe the phosphor afterglow when the UV light is turned off. Green phosphor has the brightest afterglow (10 seconds), followed by blue (15 seconds), while violet has a very short afterglow (5 seconds). The afterglow may be difficult to see in daylight; a dark environment is recommended. This handheld portable model requires 4 AA batteries (not included). Package Includes: 1 x 254nm shortwave UV lamp