quote .....................
"The dιcor on these vases does appear to have an art nouveau appearance". Well, a nod toward nouveau I suppose, but not a design image that originated in that era.
I should have given my comments a little more thought
... we've all seen books with end papers, and sometimes outside covers, adorned in what are known as 'marbled patterned papers' - feathery/rippled/wavy designs created in liquid form - coloured oils or similar on a water surface, and paper laid thereon which picks up the design. The craft dated back to the C17, and put simply
. a comb is dragged across the surface of the liquid and the teeth create the rippling in the colour - you end up with a sort of zig-zag/wavy pattern as with these vases.
With glass, it's possible the vases here owe something to a second half C19 creative invention known as 'pull-up technique - or similar - there must be people here who will know about such things - books are more my thing, not glass - perhaps there is something in Charles Hajdamach to help.
Like the vase John.