A streak is an amorphous, optically recognizable form of smear.
Examples of streaking
- Streaks arise in liquids or solidified liquids, for example when two liquids with different properties are interwoven with only moderate stirring. The insufficient melting heat leads to transparent threads in the glass , which represent a production-related material defect.
- In the production of certain synthetic glasses, the formation of streaks is specifically brought about as a design element.
- Streaks can also occur when the bare surface of fittings or windows is cleaned with a soiled cleaning cloth. The contamination results in the typical streak pattern after drying.
- When fuel or oil is applied to a surface of water, stains - possibly iridescent - are created by spreading and, as a result, by currents, wind, waves or stirring, streaks.
- We also speak of streaks in gases. This is due to local fluctuations in the refractive index or density . These can be observed , for example, as air shimmer or heat shimmer over the hot desert floor. In technical optics, this effect is used for streak photography .
Occasionally, Schliere is also used as a synonym for "slimy mass" (actually smear ).