I vaguely remember the London smogs before they cleaned up the air in the city: the roads that vanished into a mysterious nothingness and the grey outlines of buses and cars that appeared as if from nowhere. I also remember visiting the local film studios in Ealing, Shepperton, Pinewood and Elstree and in particular watching the creation of a Hammer horror movie scene with vast amounts of fog and dry ice. I later returned there to work on a couple of movies and was fascinated by the special effects machines they used to make rain and snow and the amazing make up that would take several hours to put on. Today special effects in the world of movie making have reached new heights with computer-generated imagery, and you may even experience these effects in some form in this theatre.

Theatrical sound production techniques have finally caught up with lighting in terms of computer-driven technology. There is now almost no limit to the number and complexity of sounds that might be needed for just one cue. The main limits are in terms of the number of speakers and the time required to create the sound cues as well as the important question – whether the effect furthers the story-telling or is just fun to create!

The first historical mention of a special effect relates to a dramatization of the Book of Genesis entitled Le Mystere d'Adam written around 1150. The text states that Abel had a pot of stage blood concealed on his person. The York Play Cycle, a massive dramatization of the Bible from 1474, is still enacted today, but with a substitution of the original crucifixion sequence. The whips and crown of thorns were treated with animal blood to give the appearance of real bleeding and a piece of stage machinery called a trebuchet (turntable) was used to substitute a dummy for an actor. The dummy would be loaded with animal blood and animal intestines to provide for realistic disembowelment and smells.

The Spanish Tragedy (1585) by Thomas Kyd contains eight onstage murders and suicides, a public hanging and a man having his tongue bitten out. The actor had to have a severed lamb's tongue in his mouth and other cast members hid bladders filled with sheep's blood beneath their costumes which were slit open by real weapons used in the stage fights.

The original Globe Theatre was constructed with some special effects in mind. The stage was built five feet from the ground so there was space underneath (called Hell) to hold both actors and props. Trapdoors were built in the stage floor to allow entrances and exits. There was a false ceiling over the stage also with trapdoors so actors, scenery and props could be "flown in" using wires or ropes from what was termed the Heavens. There was a cannon in the roof in an attic above the Heavens that helped create dramatic entrances and was used to recreate battlefield sound effects. Unfortunately this led to the fire of 1613 that destroyed the theatre within just two hours.

The most often used theatrical special effects are smoke, fog and haze. The military have historically used smoke and fog to mask troop movements and the same techniques and technology are used in the theatre. Smoke is differentiated from other atmospheric effects because it is composed of solid particles released during combustion, rather than the liquid droplets that make up fog or haze. There are strict guidelines about the use of fog and hazing machines, for those operating them as well as for the actors and audience members that come into contact with their effects. The safety of the special effects may not be a cause for alarm but being in the presence of a ghost may be!