The basic principal
Cut up paper and paste them on the object to be decorated.
Suitable paper for collages include paper napkins, magazine pages, paper specifically produced for use in collages, decopatch paper, artisanal paper...
You need to ask for a glue that is transparent once dry and acts rather like varnish : adhesive varnish

The advantages
It's an activity that doesn't take much time - so good for kids! The slowest stage is the cutting, if you're trying to be careful.
Many different bases are suitable : Wood

paper napkin directly onto wood Glass

Glass painting and napkin design Metal

Paper napkin design on metal Terra cotta

Decopatch on terra cotta ashtray
also objects in polystyrene (like for the Christmas ball ornament), cardboard, stiff paper, hard plastic...
Using the paper collage technique you can even cover curved objects (vases, lamp bases, curved-sided trays...)

The disadvantages
It's difficult to remove material from the napkins in exactly the way you want, the paper napkin being easily torn. Better to choose, if possible, a background in the color you wish to reveal
At the time of pasting, the napkin, wet from the glue, can tear : use a soft brush or a little sponge

Variations

To solve the disadvantages of using paper napkins, new types of paper have been developed, including large sheets of thick paper printed with different designs. It's easier to cut than the napkins because of the quality of the paper and the collage stage is easier too because the paper doesn't tear. However, once the glue has dried, the design left is a very clear one, not 'merging' in the way a napkin does. This can be a plus or a minus, depending on the effect you've been aiming for! Don't forget Decopatch paper, a strong paper that lends itself to the tear and stick technique...


[napkin paper collages step by step] [objects in Decopatch]