There are three techniques for gas-assist injection molding. One method is through the nozzle of the machine, another is through a cold runner, and the other is through the cavity of the mold. Regardless of which techniques is used, it is critical that the gas not penetrate into the barrel of the machine. If gas does enter the barrel it will certainly cause an inconsistent shot and may also cause silver streaking in the part. Ways to avoid gas penetration into the barrel are to use valve gates, increase machine holding pressure, or design long cold runners. Gas should never be injected through a hot runner manifold.