Traditionally, Dutch crafters sourced their papers from envelopes with pretty, patterned interiors, but these days, crafters use all sorts of light decorative paper, from origami sheets to upcycled coffee filters.
Iris folding patterns can be purchased on-line, in some specialty art stores or as published books. Many paper craft artists create their own unique designs.
There is often confusion between iris folding, which primarily focuses on the creation of an iris, and tea bag folding, which is more about pattern and symmetry. Both however, use similar types of folded paper with a similar technique for placement.