  The detection of NaCl at large radii in the Egg Nebula, CRL 2688, requires
densities of 10^7 - 10^8 cm^-3 in a thick shell of r ~ a few X 10^17 cm. To
explain these results, a mechanism is needed for producing high densities at a
considerable distance from the central star. In two dimensional simulations of
the interaction of the fast wind with an ambient medium, the material becomes
thermally unstable. The resulting clumps can achieve the requisite conditions
for NaCl excitation. We present 2D models with simple physics as
proof-of-principle calculations to show that the clumping behavior is robust.
Clumping is a natural outcome of cooling in the colliding wind model and
comparable to that inferred from observations.
