Speak on the topic. Separation issues for the metal casting industry include the handling of foundry and nonfoundry scrap. Gates and risers removed from metal castings can sometimes be cleaned and returned directly to the furnace, but gas inclusions often limit their recyclability. Specific impurity levels determine which pieces can be reused directly and which pieces must be diverted to other products or re-alloyed and refined. With few exceptions, foundries must have a reasonable idea of the composition of scrap in order to use it. Limitations are imposed by the scrap required quality and the cost of scrap separation. Each foundry would prefer to use only scrap produced in that foundry, but this is not generally possible. Scrap separation is accomplished in a number of ways. The best and most cost-effective method is segregation of different scrap types by the scrap generator. With this method, different types of scrap are never mixed together in the first place, and foundries have clean scrap of known composition to reuse. Some facilities, such as large iron foundries and smaller specialty foundries, have on-site scrap separation facilities. Others, such as smaller metal casting operations do not have the financial resources to operate their own separation facilities. Separation processes used at these facilities include hand sorting, identification by visual or chemical means, magnetic separation, and eddy current separation. Currently, only the most valuable metals are separated.