An outwardly propagating spherical flame has been used to characterise the influence of water addition on the combustion of variable steelworks gas compositions. Attention was given to the ratio of hydrogen and carbon monoxide within blast furnace gas, and the catalysing influence of water addition on the preponderant reaction kinetics. A nonlinear extrapolative technique was used to obtain values of laminar burning velocity and Markstein length for atmospheric combustion with air and change in equivalence ratio. Four disparate blast furnace gas mixtures were tested with increasing volumetric proportions of hydrogen in the range of one to seven percent, displacing other constituent fractions. A non-monotonic influence was observed, with propagation accelerated for compositions comprising smaller amounts of hydrogen, and the cooling impact of water addition shown to slow faster burning flames. Water addition was also shown to increase the effects of flame stretch on observed propagation rates, and the contrasting influences resulting from vapour fraction are discussed with respect to practical combustion instability, in addition to alternative synthesised fuels. Numerically modelled results were generated using the PREMIX coded CHEMKIN-PRO, and the performance of specified chemical reaction mechanisms evaluated in relation to the obtained experimental data.