Experimental study of the roughness of crumpled surfaces

We report on the experimental study of the roughness of randomly crumpled surfaces which are unfolded. This system provides a natural example of random surfaces which exhibit long-range correlations. It is shown that such rough surfaces are self-affine with a Hurst exponent H ≈ 0.9. A simple one-dimensional model illustrates the way long-range correlations may naturally occur in the crumpling process.