This piece from 2006 could very well be described in this way. A handmade collage, made with glue and scissors that I enhanced later in Photoshop.
Original size is 125x80cm
Like an unpredictable game where each random move generates a new order and a new sub context to the whole, the game only ends when you don't surprise anymore playing it.
Manipulation of content seems to be the best description of "Collages". Elements of different origins put together on a surface that wasn't meant for them.
The word collage comes from the french word "coller" to glue.
Collages and Art in general is about organizing color, form, composition, rhythm and the interplay of all these in support of the work itself.
These are the basics of visual art and as fundamental to traditional or digital art as to the cave paintings of Lascaux.
And if you see works labeled collage where people glued all kind of elements together you are correct in telling them, that it's a "montage" they have made.
If you are looking for references I could give you the explosive mixture of some baroque frescoes by Andrea Pozzo, Giovanni Battista, Pietro da Cortona, with paintings of Hieronymus Bosch, John Martin and the dramatic body contortions of Matthias Grünewald.
And Gustave Moreau is never far away.
Your Collages shoud be like the birth of feelings...the clearer your soul the more seductive is evil. The images temptations like should always bring some energy to work.
