Thermo analysis is a tool used into foundry industry of cast iron and aluminium alloys. Into cast iron field is used to forecast chemical composition of the molten metal, type of eutectic solidification and tendency to develop ledeburitic solidification or micro shrinkage, as mentioned into previous papers from authors [1, 2]. This paper presents a new methodology, developed to anticipate the potential graphite shape from a casting produced from a molten cast iron melt. This technique is used to assess the sphericity of the graphite, in the melting floor, avoiding a metallographic evaluation, speeding up and reducing the cost of the structure evaluation.