Pouring Temperature-

In general, the higher the pouring temperature, the higher is the fluidity of molten metal because of decreased viscosity. But at higher pouring temperature, the amount of dissolved gases increases significantly. Therefore, the pouring temperature should be kept low to avoid defects due to trapped gases. It is clear that gas solubility and fluidity are two conflicting requirement. The pouring temperature is, however, decided on fluidity consideration alone and the temperature of the molten metal at the time of pouring is so chosen that every corner of the mould cavity is filled before solidification begins.

Design of Riser-

Risers are designed and located in such away that the volume of riser is sufficient to compensate for shrinkage and that it solidifies after the casting. A riser volume of approximately three times the shrinkage volume is usually
Considered adequate. The location of riser is selected to promote directional solidification. Invariably, more than one riser is required and the number and their locations depend upon the configuration of the desired casting.