Astrid, I'm curious... how long have you been making themed glass displays by your front window sill? How and when do you decide which theme will be next? And have you ever repeated a theme? Ah, so many questions...
Anik - let's see. I've started collecting in january 2010, and at first I could place everything I had on the front and back. No need for display choices obviously. Around may I had acquired so much that I had to move some of it to my workroom upstairs. At first I just kept the best pieces downstairs. I think my first themed display was in June, when I had too many nice pieces and had to start making choices. I think I was also influenced by Hans (of the artglass Leiden website), who I visited to pick up some pieces he sold me. He rents a seperate storage space and once every half year he changes his display at home (he has one (or two?) large display walls with lights in it, very beautiful).
Since I had a few nice new ones in the colours blue or green, I decided to make a display in aqua and green. Green for spring and blue for the summer. Then in July I added cobalt and removed green - that had more of sea summer feel. August I wanted some multicoloured pieces out, especially my Rhapsody pieces, so I made a display where all the vases were clear with additional colours. I made a pink and red display in september for contrast (and because I hadn't seen those pieces in a while). October I wanted autumn colours (brown, amber, orange, red) and november was my first origin theme, when I had enough pressed Czech glass to fill a window sil. In december I went back to colour theme with black, white and clear for winter.
I think about my themes beforehand, but often it's only on the changing day that I make a final decision. It may be that I recently acquired something that I really want on display and just make up a theme that fits it (like the Big is Beautiful theme of february). With the theme of april, Skrdlovice, the reason was that with the big blue bowl shape I think I had acquired just enough of it to fill a window sill. The Peill at the back was made because the back window sill up till the Peill display was extremely cluttered with clear glass, and I needed to make choices in that area, and the Peill ones are my favourites so far. If I change it, it might be a Nachtmann display. I'm getting there with the number of pieces needed, and I want my Slice vase out on display soon

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Themes can be made around any aspect of my vases: type, colour, technique used, shape, size, time period, designer or factory. I was only partly focused for most of 2010, so I have lots of relatively cheaper pieces rather than a few very beautiful exclusive ones, which provides a need to change often (and I really need to sell some of it, I think, now that I have acquired a bit more focus, though I dread having to start with all that).
I haven't repeated a theme yet, though some vases come back in several theme. A big Vladislav Urban vase in blue fitted my blue-green, my blue-cobalt and my pressed Czech. One of my Big is Beautiful vases is now in my Peill display at the back.
Astrid