These blocks are stabilized (and dyed if colored) by Wood Dynamics. You will be satisfied or we will swap it or refund it, you choice.
Burl wood has natural inclusions and is considered to be part of the natural beauty of the wood. Occasionally voids show up in the wood also. The process to fill these voids in is to fill the gap with thick or gel type super glue and then sand over the void while the glue has not cured. The sawdust mixes in with the wood to give it a nearly invisible patch that blends in perfectly with the grain. If you find some cracks that make the wood seem weak, use (our friend) super glue again but this time use “thin” super glue and squirt it into the crack and quickly sand over it again. The dust will mix in with the glue and make a nice little repair and give you a solid piece. Both techniques are very routine when using burl or mammoth ivory.
Tip: To make this wood really pop visually, use Tung oil and apply it to your finished handle. Keep applying it for 30 minutes allowing the Tung oil to wick into the wood. (Stabilized wood will absorb water or Tung oil in this case like a sponge) After 30 minutes, stop applying it and let it dry. As it dries, excess oil will weep out. Wipe this off to save you some sanding later. Let it dry a couple days and sand it and buff it up with some wax. You will get some 3D look to the wood that is really nice. I would avoid using pure Tung oil. It takes weeks to dry. Find a wood finish that lists Tung oil as its major ingredient. The rest will probably be some polyurethane and evaporants. This is good. The evaporants will help the Tung oil cure a lot quicker than it would without it. The poly will just help seal the wood against moisture and dirt.