Aluminium nitride can be patterned with a Cl-based reactive ion etch. Besides photoresist, hydrogen plasmas can also etch silicon, albeit very slowly. It is commonly used to etch glass and silicon wafers. Hydrogen plasmas can also etch silicon as well. In the semiconductor industry sputtering is used to etch the target. Follow by finalizing the transistors using etch and deposition processes. Copper sulfate is used to etch zinc or copper plates for intaglio printmaking. Another application of sputtering is to etch away the target material. LightScribe is monochromatic, initially a grey etch on a gold-looking surface. Hydrogen also reacts with resists to etch or decompose them. Usually, photographic exposure followed by chemical etch or water washout. Careful control of etch time is required to prevent undercut. These changes were implemented in the subsequent version of Debian (Etch). Presence of etch channels and etch pits degrades the resonator's Q and introduces nonlinearities. Students would write using a stylus, with which they would etch onto a wax-covered board.