It may be that you're not kneading it long enough. Five minutes may not do the trick. It's also not necessarily about how long you knead it so much as how much pressure you've applied during that time. Do you twist your kneading bag periodically as hard as you can to get as much moisture out as possible? Do you crush it against the bottom of the bowl when kneading under water? Do you squeeze your fingers together and squish the wet root around in the bag a bunch?
A good indication of kneading effectiveness is how quickly the liquid in the bowl around the bag becomes cloudy with that "milky" quality. I usually knead for 10 minutes, after soaking the medium grind powder for about 5-10 minutes.
A typical prep session goes like this for me. I just had a nice Mo'i session last night, and this is what I did (and usually do):
- Got my bowl out, and put my empty dry kneading bag in it.
- Scooped out 3 heaping tablespoons of medium grind root and dumped it in the bag sitting in the bowl.
- Ran approximately 2 cups of warm tap water into the bag, and went in there with my tablespoon and stirred it all around.
- I let this sit like this (root in bag, bag in bowl) for 5-10 minutes before coming back to it. Sometimes I cruise through and stir it up again.
- Twist the top of the bag a bunch of times, forcing all the air out of the bag.
- Squeeze and squish the bag to get most of the water out of it until I start to feel the root inside and most of the water's out. What's inside feels like maybe a squishy latex stress ball, the kind that has oiled sand inside. Or maybe some really thick oatmeal. At this point, the runoff from inside the bag will be cloudy, but somewhat translucent and not milky.
- Now I do the hard work. That is, squeezing it between my fingers, squishing it back and forth inside the bag, pressing down really hard against the bottom of the bowl to mash it, closing my fist around the bag as hard as I can with my fingers separated so it gooshes out a bit between my fingers within the bag, etc. I do this for a few minutes, all the while submerged in the water.
- Then I take the bag out of the water, hold it over the bowl, and give it a huge twist and squeeze until I can't get any more liquid out of it. Lots of pressure. I use nylon bags, so I can't tear them so I try as hard as I can to tear them by twisting. Tons of pressure.
- At this point, the water should now have that milky quality. How quickly this milky quality comes indicates how well you're doing with the squeezing. Prepared kava liquid is a colloid, and should look like one.
- Then I submerge it again, and squish and separate what feels like modelling clay that's in the bag at this point until the water comes back in. I'm looking for that thick oatmeal feeling again.
- Then I go back to step 7 and repeat all of this until about 10 minutes are up.
Sometimes my forearms feel like they're on fire afterwards. If my grip strength starts to drop, I take a few minutes off and come back for more kneading. If I've been to the gym that day, I often have to take periodic breaks because my arms are already tired.
I used to knead for 15 minutes or more, but now I just do 5-10 minutes of really intense kneading and am getting better results.