Appears white under ordinary light and changes to White under black light. Color shown is approximate. Perfect for those ultra-cool dual image chalk drawings. Works great on wood, paper masonary, asphalt and a host of other surfaces (not recommended for black boards). Stick measures 1"x1"x3"
This chalk product is designed to react to a true 365nm black light source it will not react to longer wavelengths such as 385nm, 390nm or 400nm.