I think you got the wrong mop. It should wick immediately on test (about 5 inches). The correct mops have pure white strands. I bet yours are grey(ish).
They will work (for a while) if you wash them in a strong soap solution, and then rinse them out before use.

what sort of material? I had figured cotton yarn would be appropriate? What sort of yarn do the pure white ones have? Is it some sort of synthetic instead of cotton?
The yarn looks kinda natural in color, not like it has been strongly bleached.
Not a big deal as the mop head cost very little and I'm sure I can find other uses for the strings. I'll go looking for another more appropriate mop head shortly.

The mop heads they sell here are pure white natural cotton (I think), and they last forever. Sometimes they sell grey(ish) mops. But they are treated with wax. They only work after they've been in a soap solution. They don't wick well, and they don't last long.

Frankly . . . you're making me think. Perhaps the white heads are synthetic. Need to check this out. {{gwi:996791}}

Thanks grestoke.

An interesting side note on wicking action. I recently was soaking some stevia in water to make a sweetener. I had put the crushed stevia leaves in a nylon knee high so it would be easier to strain and squeeze the liquid out of the leaves. I left the top of the nylon out of the cup wraped around the handle. Later that night I noticed there seemed to be almost no liquid in the cup but the counter around the cup was wet. It seems that the nylon works very well for wicking. I had placed plastic wrap over the top of the cup but some of the nylon was exposed and most of the liquid must have evaporated as there was not that much liquid on the counter.

Anyway, I'll be looking for another mop head on my way into town today.

I read that a lot of people use nylon stockings for wicks. I use cut up old cotton t-shirts, but my wicks only need to serve the less demanding purpose of aiding drainage on the way down, not soaking the water up.

tclynx wrote:
I'll be looking for another mop head . .

Did you come right?

when I use wicks to start plants I always just use generic craft string. never had a problem. recently on my DWC system, I just installed a pump with a spayer at the top and let it spray nutrient onto the bottoms of the net pots. worked very well and had the added benefit of helping aerate the nutrient.

Here is a link that might be useful: {{gwi:1005621}}

I got a pure white mop head. Good will industries I think. I'm actually guessing that it is rayon rather than cotton.

Anyway, it seems to have worked. I was able to get some seeds started on a bit of cotton ball that was touching the mop string. The little seedlings that I put against the mop strings seem to be surviving too. I'll have to do at least a crop and a half this way to decide but I'm guessing I may like this method for my indoor lettuce set up.

You can also buy felted wool or felted nylon strips (2" wide) that wick very well. Felts wick well because they are homogeneous and wick the same in all directions.

I suspect wicks for oil lamps would work well too. Seeing how they're called "wicks"

tclynx wrote:
I got a pure white mop head. . . . . it is rayon rather than cotton.

You're right . . . the pure white heads are synthetic. They work well and last long. It's the pure cottons that are not as good.

Actually, isn't rayon wood fiber? Anyway, the cotton probably has some natural oils in it that inhibits the wicking action and cotton breaks down fast.

The Rayon yarn seems to be working well and is easy to get.

I haven't tried this but I'll bet hemp string would work well. I'd imagine it would wick, and, it used to be used for outdoor purposes a lot because of its resistance to rot... maybe worth a try possibly.

There are two options I have seen that work well but it depends on the amount of money you want to spend. Neither is really expensive but at times a few dollars makes a difference.
One is actual wicks like those used in oil lamp or kerosene heaters. You can get clean replacement wicks at a lot of Walmarts, farming supply stores(such as Rural King) or home improvement stores.

The second is braided cotton clothes line or rope. I've seem both these used to with very reasonable success though admittedly I have not used the wick system for anything larger then seedlings and then it was just to see how it would work.

In case this helps I'll share my limited experience:

I took a 2" net pot I had laying around and put in some black aquarium rock. My son had a mesh laundry bag that had a bad rip in it so I took and cut some small strips and added them to the pot letting the strips (3 in all) hang down. To this I added a tomato sprout and made a very small bubbler out of a large yogurt container. The bottom of the pot was about an inch from the water level and the wicks ran to the top of the rocks. I only turned the air on 3 times a day for a few minutes and left it off the rest of the time. This way the water got "stirred" and oxygenated but the bubbles did not splash water on the rocks or wicks so I could tell if they were actually drawing up water. They did a great job.

That said the mesh I think was cotton. It could have been a synthetic But the feel was like cotton. I have head that nearly any braided thread will work but like I said before I have not tried anything other then the little experiment.

For those wondering the plant did live and was later transplanted to a larger pot/bucket and lived a long "fruitful" life giving me many tomato sandwiches and pots of chili.