Minnesota Salad Table for Summer and Winter

[Amaranth]

Minnesota is comparing a Hydroponic Salad Table
https://sites.google.com/site/saladtableshootout/home
with a regular Salad Table
http://growit.umd.edu/saladtablesandsaladboxes/index.cfm

to see how they do both indoors and out.

I would like to figure out how to do something similar to the hydroponic table that doesn't involve plastic. Does anyone have suggestions? So far things I have thought about:

1) I have heard that there is a type of clay that ponds can be lined with so they will hold water. Anyone know what that is or if it would work on straight rather than sloping sides?

2) Could a bamboo raft be built to float the plants? How could it be designed to exclude light?

3) What could the net pots be made out of that would hold up for at least 3 months and preferably more in hydroponic water?

[Gardenarian]

1) The stuff used to lined ponds is called gley, and is made from manure. Look HERE (http://www.permies.com/t/3409/ponds/Gley-technique-sealing-ponds-dams) for more info on that.

2) I think the bamboo could work. Is it necessary to block all light? I have propagated plants in clear containers.

3) The first think that came to mind was a tea strainer! But something made of wire might work? Or could you use clay pots, as they are quite permeable?

I'm growing lettuce on a table - but it is plastic, and I'm using soil. (It's an old play table made for sand and water, I think - curbside find.)