After doing some research and networking I got exceedingly lucky and was able to obtain 20 gallons of Food-Grade mineral oil for free! Food-Grade means that it is completely non-toxic, harmless stuff, and is safe for human consumption. Normally the oil sells for $50-90 per gal. depending upon the source and grade of the oil. The particular oil that I got is used as hydraulic fluid in machines and vehicles that operate in environmentally sensitive areas such as wetlands.
The original prototype with a small electric fan to circulate the oil.
This project was very exciting for me. It is counter-intuitive to see an electrical appliance in a liquid medium, and a working one at that! And, what kind of bizarre sound will be generated by all of this? I was advised by an instructor to be aware of aesthetics, and make my piece look more music-oriented and less like a science project. He suggested that I play up the "absurdity" of my idea by making a large speaker-box façade to encase the amplifier.
A heavy plastic cart was purchased and assembled. The cart would provide a structure around which to to attach the speaker box façade. The build needed to be very sturdy to support the combined weight of the fish tank with 15-20 gallons of oil (approx. 160 lbs.) and the bass amplifier (35-40 lbs.). After the box was completed, it was moved from the wood shop into my private studio for sound experimentation and final assembly. Generally I like to work in private and will not discuss or show too much to the other students of what I'm currently working on. I also like to include some small thing or aspect that even my professors don't know about. This makes for a more spontaneous and genuine reaction from everyone at critique time, and sets up the "Oh Wow" moment rather nicely.
Almost all of my time and effort on this project went into sourcing the materials and building the speaker-box façade. Fortunately, I'm very familiar with the proper "language" and materials that go into making sound reinforcement equipment. I had to build the façade as if it were the real thing using: heavy plywood, black carpet, a speaker grill, large casters/wheels, plastic porting tubes, and metal corner protectors.
I received some much needed help from my grad student mentor who had done upholstery work before. She was able to teach me some methods and techniques that made the work go quickly.
A bass guitar was hooked up to the amp and placed into the oil bath; and a small electric fan submerged along with it. The fan was turned on and running but was not strong enough to circulate the oil properly. I really wanted a strong current to push across and against the bass strings. Next, I tried a small hair dryer a got similarly disappointing results. So I finally wised up and bought a heavy duty aquarium pump. The pump worked great, but the strings still did not vibrate as much as I was hoping for due to the viscosity (density) of the oil. The sound that was produced was a deep humming drone caused primarily by the electric motor in the pump creating interference with the electro-magnetic pick-ups on the bass. Ok, the deep droning sound was not quite what I was expecting but I had to work with what I got, for there was only one more day working day left before the critique.
I then experimented with a variety of guitar effect pedals to enhance the basic sound. After some trial and error the winning combination was an inexpensive Flanger and an Electro-Harmonix B-9 Organ Emulator.
To really appreciate the full effect one must actually be in the room where the sound can be heard and felt. When my critique group first heard the sound they stood very still, as if mesmerized, and rooted to the spot. My audience said that the sound was very compelling and yet somewhat disorienting at the same time. Some people said they felt themselves getting lost within the sound. Soon after that, everyone wanted to put their hands on the tank and feel the vibrations.