He was a celebrated portrait artist who drew the attention of Elisabeth, Empress of Austria.
Enthused by the ideas of the revolution, in 1848 Kaiser joined the Academic Legion - during this time he made portraits of almost all the main figures of the March Revolution (Josef Radetzky, Franz Schuselka, Hans Kudlich Adolf Fischhof, Carl Giskra).
After returning to Austria he developed a very profitable portrait-lithography business, with clients including Franz Joseph I of Austro-Hungary, his empress Elisabeth of Austro-Hungary, Friedrich Hebbel, Robert Schumann and Clara Schumann.
In 1867–1886 he lived in Rome again, where he devoted himself very successfully to watercolour reproductions of classical masterpieces - these reproductions were then sold in Great Britain as colour lithographs.
He then returned to Vienna and to portrait painting in oils and watercolour.