Ok time to seriously attack this humidity issue. I can't be sure what effect 38-44% RH has been doing to the plants but it can't be good. Now how to make it for cheap and still be effective.
It started with a post on another site using a pet water dispenser, sponges and a PC fan. The real issue is the possibility of mold/mildew with the sponges so I hoped to improve on it. So I need a wicking material that resists mold/mildew but has great capillary action. What fits the bill perfectly is 5/16 braided poly rope with nylon core. I cut a 12" piece and hung it up with about 1/2" of one end sitting in the water and within 3 minutes the rope was soaked the entire length. SWEET!
So the rest of the materials:
10" length of 4" PVC
2 pieces of white vent filter
braided poly rope
window screening
Aluminum tape
120mm fan
Using aluminum tape, mount the fan on the end of the 4" PVC so it blows into the PVC.
I cut 3 exhaust holes in the front. I also cut a notch in the bottom that fit's over the lip of the water dish.
Next I cut several lengths of poly rope so that they fit snugly together when laid side by side. I then sandwiched the rope between two sheets of vent filter, then sewed up the sides and across the top.
Do not sew anywhere else across the rope or you will disrupt the capillary action by "pinching" it.
Next using Aluminum tape and the window screen, create a "pocket" inside the tube that will hold the rope assembly against the exhaust holes making sure all air passes through the wet rope. Not shown is how I sealed up the bottom of the tube letting only the ends of the rope come through the bottom and into the water. Note in the final picture that the tape isn't on the bottom yet. All the air was leaking out at first and bypassed the moisture.
Tube and wicking material
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Fan
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The inside "pocket" (this is an earlier pic). I've adjusted the screen even closer to the exhaust holes causing a tighter seal.
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The result? Before 44% RH. After one hour 58% RH.
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The downside. The cats needs a new water dish for vacations.