a riser is categorized based on three criteria: where it is located, whether it is open to the atmosphere, and how it is filled. if the riser is located on the casting then it is known as a "top riser", but if it is located next to the casting it is known as a "side riser". top risers are advantageous because they take up less space in the flask than a side riser, plus they have a shorter feeding distance. if the riser is open to the atmosphere it is known as an "open riser", but if the risers is completely contained in the mold it is known as a "blind riser". an open riser is usually bigger than a blind because the open riser loses more heat to mold through the top of the riser. finally, if the riser receives material from the gating system and fills before the mold cavity it is known as a "live riser" or "hot riser". if the riser fills with material that has already flowed through the mold cavity it is known as a "dead riser" or "cold riser". live risers are usually smaller than dead risers. top risers are almost always dead risers and risers in the gating system are almost always live risers.