Aside from the spiritual care taking of a keris, it is also important to consider the following two main technical reasons for maintenance: (1) keeping the blade clean; and (2) preventing the occurrence of rust.
In order to keep the blade in good condition, it is advisable to use quality certified oil (‘minyak‘), like industrial or gun oil. Vegetable or animal oil should be avoided, for using this kind of oil can easily cause the blade to become affected with mould. It is important, therefore, not to apply too much oil onto the blade. Furthermore, the excessive oil will be absorbed into the warangka, which obviously will do more harm than good.
Generally speaking, a regular check-up once in every two or three months would suffice. Then, whenever the blade seems to display signs of deterioration it is advisable to treat it with arsenic. However, one should take notice that the blade should only be cleaned (‘marangi‘) and etched (‘warangi‘) when necessary, for else corrosion will soon begin to appear. Though in many cases, due to the toxicity of arsenic, it is often a wise decision to leave the cleaning process up to well-experienced keris cleaning expert. For the rest, one should also bear in mind to store a keris in a place that is neither too humid nor too dry. Additionally, the keris sheathed in the warangka can be wrapped in a piece of soft cloth for maximum protection against environmental conditions.
Reference: ‘Majalah Pusaka Keris – Khasanah Budaya Nusantara‘ Vol. 1. Jakarta: 2007. p. 33.