This is a recounting of something I have seen, it is most definitely not any sort of recommendation for anybody to practice.
Before I met Pak Parman ( Empu Suparman) I had already been staining blades by use of several different methods, at that time I found the most effective to be the brushing method. Pak Parman introduced me to a different method that produces by far the best results of any method I have tried. I will not give any advice here, nor in writing, on how to use this method because it is has far greater potential for danger than any other method.
However --- when I was taught this method by Pak Parman, it started from buying the warangan and grinding it up to a powder.
This grinding was done in the mortar and pestle that his wife used in the kitchen to prepare food.
Admitted, Pak Parman placed a piece of plastic bag over the grinding surfaces of both mortar and pestle, but this plastic soon broke through, and the reason he used the plastic was not to prevent contamination of the kitchen utensils, but to prevent loss of too much of the warangan --- Javanese mortars and pestles are made from a very grainy volcanic rock that has a pock marked surface which retains some of whatever is ground in it.
Pak Parman lived into his mid-seventies, and his passing was due not to the effects of arsenic, but due to the effects of an even more deadly poison:- TOBACCO.
Arsenic has two faces.
Yes, we know it as a poison, but it has been used as a medicine since ancient times.
http://molinterv.aspetjournals.org/c...nt/full/5/2/60
This article is worth the read.
The length of time that warangan or arsenic needs to be allowed to stand after mixing up the suspension depends upon the method used.
For both my preferred method, and for the brushing method, ten or fifteen minutes is usually sufficient, just enough time to allow the floating droplets of powder to sink to the bottom of the fluid.
If using the soak method it is necessary to allow the powder to sit for longer in the fluid.