You purchased your kava and found that the grind isn't necessarily to your liking. You may prepare your kava root by kneading it and don't feel as though those chunks will release their kavalactone goodness. 

Don't be worried, there are a few ways you can take care of this. 

First get a large bowl a a larger sieve with a handle. The bowl should look like it'll hold at least a gallon of water when you're working with about 1kg. The sieve should have small enough holes to not let the big chunks come through but not so small as to only let the finest powder through. Most grocery stores sell these in their kitchen section. 

Next you'll need a coffee grinder or mortar and pestle for your kava root chunks. A blender will also work but, one of the nicer ones that can make a flour. Blendtec is our favorite brand of these types.

From here you will use the seive to strain out the larger chunks of you kava root. You'll be left with all of those large chunks.

If this amount is much larger than about 1/10th of your bag. I recommend that you contact your supplier. The more above that amount, the more I highly recommend you do that. Let's say it's about half your bag. That's way too much and your supplier should not be sending customers root this thick unless you're specifically ordering "tea cut".

If it's about a Tenth or your order plus or minus a bit is fine, then move on to the next step.

Add your chunks of kava root & pestle to your mortar little by little. Start grinding it up using your pestle. Do this until your satisfied with your level of grind. 

You might prefer this grind to the grind you get from anywhere else because you're doing it to your specific taste. So it's a bit if a nice surprise to get a bit of this separated out every so often.

The blender or coffee grinder method is much the same. It's much much faster to get it all done. However, it can heat up too much if you're not careful and it can get too fine of a grind. Use the pulse option. Also get a long spoon to to dig out any stuck kava from the sides...when it's not on of course.

Now your full batch is ready to go. Now power needed just your kava root and pestle.