pH-I Static has a unique colour change marker that will change from yellow to red when exposed to strong acids. Even a 20 seconds exposure to some acids can weaken a rope by 25%, compromising safety. Longer exposure will increase this strength loss. pH-I Static (Permanent Halochromic Indicating) offers a clearly defined permanent colour change, indicating when a rope has been compromised by strong acid chemicals and should be retired. pH-I Static is a Type A BS EN 1891 certified static rope with all the usual benefits of Marlow Static LSK.