Shielding material (lead) in transportation packages melts during regulatory thermal tests. An experimental investigation is carried out to study the melting of lead contained in a scaled stainless steel cuboid. The size of cuboid is 50 mm x 50 mm x 60 mm. Two side vertical walls are maintained at a constant heat flux boundary condition. Top and bottom walls are thermally insulated. Visualisation of solid liquid interface movement during melting of lead is carried out using infra red thermography. Infra red thermography is an easily available and non-intrusive method for the characterization of melt front during melting of opaque materials. This method demonstrates dynamic capture of the progress of solid–liquid interface under the effects of natural convection without contact, continuously and directly. Numerical study is also conducted for simulating the melting phenomenon. Results are compared with one wall heating and selection of proper characteristics length is suggested.