Autowaves spreading in a thin layer of the BZ  reaction with
    ferroin catalyst immobilized in silica gel have been 
    studied. It is found that there is a critical thickness  of 
    this layer such that autowaves could not  propagate in
    thinner layers. The results of computer  simulations  in the
    two- variable Rovinsky model qualitatively fit the 
    experimental  data for the used temperature range.