Hygrolon ....plastic mesh

[katsucats]

Ray, I think the LECA might wick some water away, but it would also hold more water than air. With the fabric exposed to air on both sides, I posit the evaporation of moisture out of the system would be faster than if some LECA wicked some of the moisture, but held onto it.

For example, if the evaporation rate was faster than the wicking rate, then the LECA above the water line in S/H would be dry. But we know that there is a gradient of moisture only a certain distance above the water line, and the water doesn't move continuously up the pot (e.g. imagine if you had a really tall S/H pot). If the LECA wicks some of the water and holds onto it, while the fabric material keeps pulling water up from the reservoir, that would actually be the intended effect. The fabric just has to be thick enough to pull water near the top before it gets fully wicked.

It helps that when I flush, the LECA will be pre-wet, and also that the LECA is surrounded horizontally and could only evaporate a limited distance upwards, or otherwise back into the fabric, if the fabric becomes drier than the LECA (which shouldn't be the case as long as there's still water in the reservoir). If the fabric is much more efficient at wicking than the LECA, then it becomes in effect a vertical extension of the reservoir, in my opinion, and the LECA remains the actual medium.

The difference is instead of dictating reservoir height by the height of the holes on the side of the pot, the reservoir height is dictated by the fabric properties or number of layers.

Spiffy, that's an excellent idea!! I may be able to fit a reservoir on top and let it wick downwards. Then I won't have to worry about the water not reaching the top. Thanks for the tip!

[Spiffy]

Originally Posted by katsucats

Spiffy, that's an excellent idea!! I may be able to fit a reservoir on top and let it wick downwards. Then I won't have to worry about the water not reaching the top. Thanks for the tip!

As it may not have been obvious from the photo/desc. - no need for a reservoir on top as it's just a hollow container. I fill so that it overbrims slightly and runs down the side and into the drip tray. Then what's left inside wicks up and over the edge for the next few days.

That said, the limit on these things is the wicking power of the material. I think realistically max height is about 25cm. If you wanted to go larger then possibly your idea using a clay pot reservoir on top would be better.

If you search on this forum there's something similar using two clay pots silicone'd together, surround with sphag moss + then sealed within mesh material (or I think two dracula-type mesh pots joined together). Think it's referred to as a 'jungle log'. I may give this a go myself soon!

[Ray]

Originally Posted by katsucats

Ray, I think the LECA might wick some water away, but it would also hold more water than air. With the fabric exposed to air on both sides, I posit the evaporation of moisture out of the system would be faster than if some LECA wicked some of the moisture, but held onto it.

For example, if the evaporation rate was faster than the wicking rate, then the LECA above the water line in S/H would be dry. But we know that there is a gradient of moisture only a certain distance above the water line, and the water doesn't move continuously up the pot (e.g. imagine if you had a really tall S/H pot). If the LECA wicks some of the water and holds onto it, while the fabric material keeps pulling water up from the reservoir, that would actually be the intended effect. The fabric just has to be thick enough to pull water near the top before it gets fully wicked.

It helps that when I flush, the LECA will be pre-wet, and also that the LECA is surrounded horizontally and could only evaporate a limited distance upwards, or otherwise back into the fabric, if the fabric becomes drier than the LECA (which shouldn't be the case as long as there's still water in the reservoir). If the fabric is much more efficient at wicking than the LECA, then it becomes in effect a vertical extension of the reservoir, in my opinion, and the LECA remains the actual medium.

The difference is instead of dictating reservoir height by the height of the holes on the side of the pot, the reservoir height is dictated by the fabric properties or number of layers.

Wicking involves four aspects: absorption, surface tension, proximity of “neighbors” and evaporation. The greater the absorption and/or proximity of neighbors, the faster the wicking.

LECA absorbs better than polymeric fibers as the tiny pores take full advantage of the ability of surface tension to fill voids, but the contact area between particles is relatively small. Polyester fibers do absorb water to a very limited degree (compared to porous clay), but it is the small voids of the weave and their close proximity that is Hygrolon’s “claim to [wicking] fame.”

Clay pellets have more air exposure per unit volume, so the evaporation rate is greater. However, if the evaporation rate is minimized, both will be wet clear to the top of the column.

[katsucats]

Spiffy, I think I get how your system works. I have the desire to try to get the roots to grow towards the center of the system as opposed to just around the perimeter, though. For me, I could still make use of your suggestion by putting a reservoir over the LECA in the center.

Ray, you may be right about the absorption and surface tension. I don't have data for any of the materials. With the geometry accounted for, it may be moot.

Air exposure per volume however, since the LECA has more depth, I don't see how it could have more. Like the other factors, we can't just take them in a vacuum, we must take into account the geometry of the system. So imagine a single sheet of fabric, 1/8" thick, cut out in a unit square inch. Placed vertically, it would be exposed to air by the left and right side, or 2 square inches of exposure per 1/8 cubic inches of volume. A 1-inch diameter LECA ball would have pi/6 cubic inches volume and pi square inches surface area. So per unit volume, the fabric actually has 2.7 times the air exposure.

As we add more LECA in the middle though, it would trap more moisture and decrease evaporation.

Well, there's no point in speculating whether it would or wouldn't work. I'll build a proof of concept once I get my hands on another 50L of LECA and some Monto clay.

[Ray]

Yes, but they aren't 1" diameter balls...

You might be right here, but this is my thinking:

If the spheres were perfect spheres and uniform in size, they would occupy about 60% of the volume they take up, no matter the size. The strip of fabric - because of the tightness of weave (small pores) - occupies a greater percentage of the volume it occupies. Because the voids are essentially full of water, they totally fill the void space.

So the spheres occupy 60% of the cubic foot volume pot they are in, but with a piece of fabric that's 12" x 8' x 1/8", it's external volume is also 1 cubic foot, but the unoccupied porosity within is much less than the 40%.

[katsucats]

I see... But at least in my case, I'm not using the fabric for the same role as LECA. The fabric will only be used on the circumference of a cylinder (as shown in the picture several posts ago), and the LECA will fill the center. I think your analysis would be spot on if I was debating whether to fill the center with LECA or a whole roll of the fabric.

Yes, using LECA would dry the fabric more compared to using a hard plastic backing, but that's the trade off for increasing the root zone volume by up to 16 times. I could even split the difference by putting a plastic reservoir in the middle, separated by LECA, to give e.g. Bulbophyllum roots 2-3" to grow into. Now I'm wondering if it's possible to connect wicks to the sides of a reservoir with a gasket. I don't have much building experience.

[Ray]

Either put a reservoir at the bottom and rely 100% on wicking or rig a up a way to trickle water down from the top and let gravity do most of the work.

A central, cylindrical reservoir with wicks to the Hygrolon will tend to drain itself rather quickly, leaking on the floor as the hydrostatic pressure will push the water out faster than it can be wicked up.

Now then, if you can wrap the fabric around a porous ceramic body like a cool-log or even a clay flower pot, the leakage through tho pot wall will be better contained.

[DirtyCoconuts]

Keep in mind that wicking materials that absorb, like a violet wick or shoelaces will concentrate the fert and salts as they are almost impossible to flush.

I like the idea here but the more materials you introduce the more issues you will have with their interaction

One idea I’ve had is to place a shot glass in the top of the mount with little edges of the hygrolon in the glass. You can add water there and it will be pulled out and down but not too much that it will all leak out

[Ray]

Originally Posted by DirtyCoconuts

Keep in mind that wicking materials that absorb, like a violet wick or shoelaces will concentrate the fert and salts as they are almost impossible to flush.

Not necessarily.

The 3D mesh is most likely polyester fiber, which has very little surface porosity with precipitating solids to “grab onto”. Sure, there can be some precipitation as droplets held in the mesh evaporates, but there is little-to-no bond to the fibers, so they easily brush off when dry or rinse off with water.

I used the US equivalents for years and saw only minor accumulation of minerals.

[DirtyCoconuts]

I was not speaking about the hygrolon...I agree with you about that. He mentioned connecting wicks to the side of the reservoir, that precipitated my comment

If he uses hygrolon strips as the wicks that would probably work.