Faux
stained glass projects on glass or plexiglas using Pebeo Vitrail
paint are intended to remain inside. This is craft work afterall.
If
you would like to expose your project outside, there is no warranty
that it will remain intact. I guess it all depends if you expose
it to rain and direct sunlight or not.
Since
the paint will peel-off if immersed in water, I expect the same
thing to happen to your project if placed outside.
Now,
at a minimum I would:
- Coat it with
UV resistant varnish, especially if your project will be exposed
to direct sunlight.
- Bring it inside
for the winter season, especially if temperature falls below
freezing point.
- Consider to
re-paint, as needed, colors altered by the sun's exposure.