SLIMED

Recently I was asked to provide a slime explosion for a television ad.

 In the spot, I was told, a kid jumps up and punches an object,
causing it to explode and soak the kid (and the room)
 with gooey slime. 

This was a last minute job and they asked me to prep the
 job the day before the shoot.
This is not enough time to figure out and troubleshoot a rig like this.

 Since I was working, I called on friend and

 fellow rigger Ashley Hollister to do a preliminary day of prep.

We talked it over and came up with this idea: 

  A bowl full of liquid with a larger flat plate suspended just above it.
 Through a hole in the flat plate an air mortar would blast

 a shot of air, forcing the water/air frothy mix  out through the space between the bowl and the plate. (An air mortar is simply a pressure tank with a large diameter, quick acting valve which empties the tank instantly, creating a powerful blast of air). Here is a picture of an air mortar: 

The valve is an air operated butterfly valve, it opens quickly and offers little resistance to the airflow.

 Here are pictures of the rig being tested at Ashley's shop in Brooklyn:

 

We thought it looked promising.

However, the following day at the tech scout (a walk through at the filming location with the creative team and the heads of each department), it became clear that it wasn't.

The director's wish was for something more like an explosion in all directions, a "hand grenade" is how he put it.

So we tried modifying what we had, and came up with this:

 

 

While this created a satisfying bit of mayhem, it was clearly time to take a different approach.

The idea of the liquid hitting a plate still seemed right, but we needed a way to have it hit a 

vertical plate from behind, causing the liquid to spread in all directions.

Here is what we came up  with:

The blast from the air mortar travels through the blue hose and enters the cylinder on the left.

A measured amount of slime has been poured into the apparatus from the top, through this valve:

The valve was opened only to fill the rig with slime. The ball on the right was to deflect the slime out of the back of the rig, the plumbing cap on the left deflected the slime on the camera side.

When the air enters the rig it pushes the slime up and out both sides of the tee.

Here is a test of the rig:

  

As you can see, it worked quite well and everyone was happy with what we came up with.

We also made a smaller version of this for some tighter shots of slime hitting people and things:

 

This slime gun works on the same principle but has a self contained "air mortar".

Here is a test we did with this gun:

This gun worked ok, but saw limited use. As is often the case on this kind of job, it's hard to beat the flexibility and speed of a prop man with a bucket when it comes to heaving slime.

Speaking of slime, it was concocted from a secret recipe by Propmaster Pete Wright and his crew.

We made a hell of a mess.