The Stamps Of The Netherlands Indies.

Registration Labels BATAVIA (modern day Jakarta)
First time seen a weight option on a registration label.

1912

A lover's note, on the back of an Netherlands Indies stamp.

If you SOAK early Netherlands Indies, expect these results
As I understand it, it is not FUGITIVE INK, rather, the stamps were printed on GUM ARABIC finished paper
Source: Jan Doggen and Galeoptix 2004

Scott : Water Soluble ink Nos 164 -188 and first printing of #163
design disappears when immersed in water

Galeoptix on his website refers to 'afwasbare inkten,' suggesting the ink was fugitive.

However, the NVPH Speciale Catalogus remarks for the 'Vürtheim' numerals as issued 1902 - 1909, there was a printing in 1912 on specially prepared paper to prevent washing off of the cancellation mark. This is called 'loslatende kleuren' that, literally, translates into 'detachable colours.' This paper has shiny wavy lines at the front.

This also happened with the 1 Gulden and 2 1/2 Gulden stamps, first issued 1906. The catalogue states the paper for those two stamps, in 1912, was treated with an indigo solution that causes light smudges when the stamp comes into contact with water.

The 'Seegers' stamps of Queen Wilhelmina, with the exception of the first printing of some values also was in 'loslatende kleuren.'

The 1934 -1937 series was printed in 'loslatende kleuren.'

He probably updated his research then, in the intervening years.

He, probably, used confusing wording. I find Rein was good in technical details, but lacking in writing skills. His website is a very difficult read.

Reading the catalogue, his words can also be interpreted differently.