He graduated in the Art School of Fine Arts and Industrial Design, where Lajos Ujváry was his master. Later at the Hungarian University of Fine Arts he studied under Tibor Bráda. Gyula started work as restorer in the Hungarian National Gallery and later in the Széchényi National Library.
While working on perfecting his personal style of painting he also worked as a restorer, he became a well regarded expert in restoring old photographs, especially Daguerre.
During this period he studied the old masters of the 17th and 18th Century, particularly the 17th Century Master Jan Davidsz de Heem (1606-1683). His studies coupled with his eye for detail as a restorer led him to begin painting very detailed still life and floral subjects using a traditional technique.
Siska’s paintings have been exhibited in Hungary since 1985 and are now being collected worldwide.
When the Pope visited Hungary he created an extraordinary work of art in collaboration with a sculptor. It was a circular copy of the famous Torino Shroud, a mixed media with bronze and photography.