  We study a model of random uniform hypergraphs, where a random instance is
obtained by adding random edges to a large hypergraph of a given density. We
obtain a tight bound on the number of random edges required to ensure
non-2-colorability. We prove that for any k-uniform hypergraph with
Omega(n^{k-epsilon}) edges, adding omega(n^{k epsilon/2}) random edges makes
the hypergraph almost surely non-2-colorable. This is essentially tight, since
there is a 2-colorable hypergraph with Omega(n^{k-\epsilon}) edges which almost
surely remains 2-colorable even after adding o(n^{k \epsilon / 2}) random
edges.
