The Air Squib is primarily used on actors’ garments creating a hit effect. But it is also possible to rig it so that it shoots the stage blood on the inside of a glass. This effect will look gruesome as the drops trail down the glass in an ominous way. From a visual standpoint, the red splosh is also quite visible even after the actor is “out of the picture” (pun intended!)
Remember, timing the effect is easy as the radio control allows perfect timing while the technician looks at the monitor. This way, the actor is never really certain when the effect will happen, making certain the reaction does not come before the hit appears.