What is a Ganzfeld effect? The Ganzfeld (German for "complete/full field") effect happens when the sensory system is steadily overloaded with a uniform signal. For example, a uniform, steady and all-encompassing soft light to the eyes will cause a "loss of vision", as there are no visual features present for the brain to interpret in a meaningful way. When the condition persists while the brain keeps on trying to manage the situation, hallucinatory images can appear.
The Ganzfeld is interesting because it is a simple, yet effective tool which provides a mild form of sensory deprivation. The effects of sensory deprivation include hallucinations, relaxation and time distortion - it's like turning on the screen saver in your brains.
Mild sensory deprivation through the Ganzfeld effect gives mild effects. The sensory deprivation effect can be deepened, but be advised that for prolonged total sensory deprivation there will also be some adverse effects, for example loss of identity, apathy and depression.
To enhance the effect, the basic idea is to extend the Ganzfeld idea to other senses than vision. For example, you can use earphones with white noise sound to prevent hearing any structure, wear thick gloves on hands to prevent touch sensations, and so on. In such a multimodal Ganzfeld (MMGF), dreamlike, pseudo-hallucinatory images are frequently induced.
While trying out the Ganzfeld with a big blank wall in a darkened room, for a short period of time I saw myself in a snowy parking lot. After that I saw as if I was sitting on the ground at street level and people were walking by - I could see legs of people walking by.
On another occasion, I was sitting down and used ping-pong balls (see below). I moved my arm a bit, and could spot this from the corner of my left eye as the ping-pong ball wasn't a perfect fit. This slight movement became a feeling of a very reptile-like slithery motion below me, something like the tail of dark crocodile going by, lasting for only a fraction of a second. I thought the association was fascinating - why a reptile? Why not a rock, or a fish?
Experimenting with the Ganzfeld Effect
The easiest way to start with is to block out the visual senses.
First, cut a single-colour ping-pong ball in two. Make the cut slightly wavy to fit the eye socket better. File the sharp edges down a bit e.g. with a nail file. Now, place the ball halves over the eyes. Operating the device is likewise easy: while wearing the apparatus and keeping the eyes open, shine a light source at the ping-pong balls. The visual field should appear to be of an uniform colour and intensity. Stay still and just relax your eyes while staring at the uniform visual field.
Swimming Goggles and Frost Spray
One reader sent a tip to spray the outside of swimming goggles with frost spray which is used for making e.g. frost-like window decorations. I tried this with Speedo goggles but the spray didn't really stick to the plastic for some reason. In addition I broke the rubber band the first time I attempted to wear the glasses. This process might work for you though, and if it does, the resulting glasses will be easier to wear than ping-pong balls.
Even without glasses, you can also achieve a kind of Ganzfeld effect by staring at a stationary point for some time. The eyes should not move. Eventually the vision will begin to fade out, and will return once the eyes are moved enough. Starting to see an afterimage is a good sign, but it also means your eyes are moving. It may help to try to reduce the rate of blinking. Also, it might be easier to experiment with a large area of uniform colour, such as a wall.
Extending the Ganzfeld Effect to Do Basic Sensory Deprivation
If you want to block your aural senses, put earplugs into your ears, or play noise for example with a portable music player. To avoid background noises, e.g. traffic noises from outside, sports earphones which go inside the ears, or more expensive active noise cancellation earphones work well. If you use earplugs, you'll be hearing a silent noise-like whoosh sound which is the sound of circulating blood - like music from your body.
To block the touch sense of your hands, you can wear gloves, or cross the fingers of the left and right hands, or place the hands inside each other, and so on - find a configuration which feels comfortable. After some time, the hands will feel like a uniform warm mass and you cannot feel your individual fingers.
For some "real" sensory deprivation, you can check around if there's a spa with a "sensory deprivation tank" in your area.
I tried a flotation tank once at a spa but it felt slightly cramped for my height. My arms ended up bumping to the inside of the tank while floating there and it was slightly distracting - a larger tank would've been better. However, the biggest distraction was the inability to relax my neck properly, a pillow would've been good. Nevertheless, once the lid was opened, I was surprised and thought something had gone wrong because just 10 minutes had passed and they opened already now. Instead, it had been 45 minutes and my time was up. I couldn't test the tank again, but all in all it was a pleasant experience which I would happily try again.
Uses of Ganzfeld
The Ganzfeld effect can be used in combination with other methods which do not require inputs from the senses. For instance, a Ganzfeld effect could be desireable during visualization or relaxation practices to reduce distractions and to deepen the state of visualization and relaxation.
Also, the mild hallucinations might be interesting to experiment with. Since it's hard to command dreams to appear at will, Ganzfeld is a good alternative for gaining better access to your brain's capabilities.