I bought 3 cherry burls at an auction.
I roughed one out and it is "interesting". There are voids and places where the wood is rock hard next to places where it is punky. Needless to say, it is tough going. The results might be pretty, or they might be trash; too soon to say, I an not even sure if I can finish it without it breaking apart.
Is this typical for a burl? Anything to be done to make it easier?
Cherry burls frequently involve folding of more "normal" grain sections between the rapidly-growing sections. Traps bark, moisture and grit in there, which leads to the white rot you noticed.
It's like the box of chocolates, turning burls. Just keep repairing as soon as you detect a fault or be prepared to eat some wood.
Assume I am ignorant. What do you mean repair? I have some Captain Tolley's Crack Sealant, which I have put in some of the cracks to secure them; but it obviously does nothing for the voids.
voids are your friend - they add character to the finished piece
Voids are optional. You can leave them as a "feature," as Bill suggests, or you can keep some bark on hand to stuff into a void pre-treated with medium CA for a "natural" look of another sort. Some like the unnatural look of color (inlace) fills. If you decide to go for feature, you'll have to decide if you want to firm up the white rot that lines the voids or remove it with a wire brush. Same as with the outer bark, really.
What you must repair and monitor are the cracks that run from the voids or occur at random through the piece. First click you hear is a stop, search and repair situation. It's not a one-time deal, either. You'll want to keep up with them as you approach your final shape. Since I turn outside/inside, I run masking tape around the outside as a dam for the glue I'm putting in the cracks. Even with a pre-treatment accelerant spritz, the stuff can run some amazing places and remain liquid for a long time, so be careful.
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