The Spanish authorities quickly suppressed the use of "quipus". Extensive handling of "quipus" can also increase the risk of further damage. Even when people have tried to preserve "quipus", corrective care may still be required. The "quipus" were made of colourful threads or cotton/fiber strings. These "quipus" were exchanged during an 18th century rebellion against the Spanish government. According to Guaman Poma, "quipucamayocs" could "read" the quipus with their eyes closed. Eielson's quipus were exhibited in the 1964 Venice Biennale to wide acclaim. Quipus are also believed to record history and literature. "quipus" regularly contain sums in a systematic way. "Quipus" are now preserved using techniques that will minimise their future degradation. "Quipus" are also closely monitored for mold, as well as insects and their larvae.