What wicks best?

The first experiment I am doing is to test the wicking capability of various materials. I am filling 50mm diameter Perspex tubes with the material and placing the bottom of the tube in a container of water. I am measuring the height that the water rises in the tube.

The graph below shows the height and rate of wicking from my first round of tests. I will be repeating this a few times to see how consistent these results are.

The materials I have used are:

• Crushed gravel - 10mm crushed basalt
• River gravel - 10mm rounded river pebbles
• Scoria - 15mm scoria
• Sand - washed sand
• Sand+gravel - mix of sand and 10mm river gravel from Corkhill Bros
• Crusher dust - finely crushed basalt
• Woodchips - small (5-10mm) wood chips
• Cocopeat - uncompressed and dried cocopeat
• Three soil mixes from Corkhill Bros - super soil, garden mix, vegi mix

The river gravel and scoria had almost no wicking ability so they would not be able to transfer water from the reservoir to the soil in a wicking bed. The crushed gravel was a bit better, wicking water up 150mm after almost two weeks. This gives the impression that this gravel may be ok as a reservoir layer (no more than 150mm deep) but the rate of wicking was slow and the amount of water wicked up was very small.

The most impressive wicking was from the crusher dust. Water rose through this to the top of the tube (470mm) in only two days. Sand also performed well, wicking up 385mm (sand+gravel) and 365mm (sand). It would appear from this that sand would be better than gravel in the reservoir of a wicking bed. Crusher dust wicks even more but I have never heard of this being used in a wicking bed. I need to look into this further.

In the next blog post I will look at wicking in soil, cocopeat and woodchips.

---