Window art largely dominated the initial phase of my glass painting. It was nothing else but painting all sorts of themes with glass paints on a piece of an acetate sheet. It was a good way to practise piping curves and straight lines. After I had finished and the paint had touch-dried, I trimmed the edges of the remaining acetate and placed a vitrail acetate picture on my windows using repositionable sticky dots. No problem if you want to wash your windows :) Simple peel the picture off and replace it when you're done. Simple, isn't it?
The advantage of glass painting on an acetate over painting with real peel-off window art paints, is that your painting on an acetate will never melt on the glass even if exposed to a strong sunlight for a long time, which is exactly what happens to some peel-off window art pictures. They seem to become fragile with time and start cling to the glass so tightly that it's virtually impossible to take them off your window after a while and they tear to pieces. Cleaning windows turns into a nightmare then. Acetate will never let your glass paints come in direct contact with a glass pane hence no danger of paints melting on your windows.
I also recommend this type of glass painting to all glass painting beginners as painting on a flat surface is easier and should come first before painting on glassy curved surfaces. Simply lay down you pattern underneath an acetate, secure it with a masking tape and off you go! Having fun, piping away your relief lines :)
A clear acetate can be obtained in all well-stocked crafts shops or simply try using an OHP foil. Ultimately you can even try laminating some empty laminating pouches and then paint on them! (oh, yes, I have tried that! not ideally clear but will do if you've got no acetate at hand) Acetate comes in different formats: A3, A4, A5 as well as in different thickness.
Below, here is another batch of my acetate window art pictures. They can act as lovely suncatchers as the sun rays shine through them revealing wonderful vitrail colours - so intense and suffused. Et voile! Gorgeous play of colours and sunlight in your house. Feeling cheerful already? :D