A serious issue in dealing with scientific systems at "ultra-cold" temperatures, solid nitrogen turns out to be a great hindrance when dealing with very cold systems. The majority of high-vacuum and cryogenic laboratory systems are constructed from stainless steel, which, despite having a specific heat far lower than that of water, nonetheless is expensive to cool down by immersion in liquid helium, due to its high cost, as compared with nitrogen. To solve this problem, a lot of such systems are brought down to liquid nitrogen temperatures through being filled/immersed in liquid nitrogen, then further cooled with helium to their final temperature. Because of this, residual nitrogen, which freezes at about 55 Kelvin (at 1 atmospheric pressure) can stick around in these systems, becoming a serious impediment to the smooth operation of low-temperature valves and mechanisms.