I am having doubts and reservations about the Membrane Meniscus technique.
I decided to run some more tests based on how I plan to setup the Membrane tote. I have been planning to follow the original patent drawings and details pretty closely.
That would be a layer of perlite in the bottom of the tote, with a water inlet on one end and a drain on the other end. The nute solution is supposed to flow slooooly through the perlite. The water level needs to be just at or barely below the top of the perlite. The, the "membrane" sits on top of the perlite. Its purpose is to allow water to wick up to the root zone but prevent the roots from getting into the perlite. The roots are NOT supposed to be sitting in water. Only a thin film of water - the meniscus - is supposed to be touching the roots.
That all sounded good to me, and when I ran my first test of the rip-stop nylon I have using just water, it seemed to work fine. That test was just filling a jar to the top with water and setting the nylon on the top and then placing a cardboard tube on the nylon and seeing the water wick up the tube. That worked ok, but the water was actually touching the nylon in that test.
I put some perlite in a jar and added water almost to the very top of the perlite. Then placed the nylon on that and stick another cardboard tube in there with a small weight to hold it against the nylon and perlite. Wicking does occur, but it is really sloooooooooooooow. Im having a hard time imagining this will be enough water to let a plant grow properly.
So I ran a second test using the silk screen. It lets water flow through it very freely where the nylon does not. The wicking action is much better, but its still pretty darn slow.
It looks like my nylon just doesnt wick fast enough to work, so maybe I have the wrong kind of rip-stop or its too dense or something. The silk screen however, is a lot more porous than what he describes as the perfect material - I think.
Im going to have to go re-read his notes and details to see if I missed something. If it wasnt for the rave reviews I read and pics from several different growers, I would doubt this could possibly work. Actually, Im doubting anyway....
Left is the rip-stop and right is the silk screen after about 15 minutes.