Method of using a chisel for a crust breaking facility

Process for breaking the solidified crust on an electrolytic cell by operating a crust breaker fitted with a chisel which comprises providing a chisel having a cross-sectional dimension and having a vertical sidewall with at least one projection in the lower region of the vertical sidewall, wherein all surfaces of said projections extend outwardly substantially less than said cross-sectional dimension to minimize the danger of deformation, wherein said surfaces extend outwardly a sufficient distance to avoid jamming, penetrating the crust with said chisel, lowering said chisel further at least until the lowest projection or projections reaches the lower half of the crust, whereby a gap is created in the solidified crust which prevents the chisel forming an opening which is a close fit for the chisel.