Black stain spreading on keris during vinegar cleaning

[Anthony G.]

Originally Posted by milandro

this seems to be a possibility, along with light and temperature being the activator of the process.

There is a lot of empiricism involved in this and very little science. The person who washes my krises all of a sudden went through a phase when the warangan no longer responded en was ineffective. Now he says everything is back to normal.

I don’t think he knows why.

If rice water with minute amounts of arsenic combined to sulphur produces modest amounts of arsenic sulfide and these stain the blade even in modest amounts that may very well be the reason why the salt-sulphur method works

I was told by a friend who said that temperature of the surrounding during the time of 'washing' plays a role/part.