Carpentry is another profession learned through apprenticeship. An apprenticeship is a system of training a new generation of practitioners of a trade or profession with on-the-job training and often some accompanying study (classroom work and reading). Apprenticeship also enables practitioners to gain a license to practice in a regulated profession.
A black light is a source of electromagnetic radiation that emits near-ultraviolet light, usually in the 350-375 nanometer wavelength range. This range is just slightly below the 400nm that human eyes can detect. When this light is reflected off certain materials, it looses energy and its wavelength expands to over 400nm. The reflected light is then visible to human eyes, and the illuminated objects appear to glow.
Black is the darkest color, the result of the absence of or complete absorption of light. It is the opposite of white (the combined spectrum of color or light). It is an achromatic color, literally a color without color or hue. It is one of the four primary colors in the CMYK color model, along with cyan, yellow, and magenta, used in color printing to produce all the other colors. Black was one of the first colors used by artists in neolithic cave paintings.