Are burls dry? Are burls dry enough to work? Are they stabilized? These are questions I often hear from customers. Let me tackle the topic of dryness first . . .
While some of the products I offer - like slabs if I've had them stickered for air drying for a lengthy period - may be dry for my local climate, I generally recommend customers treat all purchases as green. When I ship orders, I wrap all burls and hardwoods in plastic stretch wrap to protect your purchase in transit. You may want to leave your order wrapped allowing the burl/hardwood to acclimate to your climate, but it is not necessary. Should you choose to leave them wrapped for an extended period, I recommend you cut a couple/few small slits in the wrap.
The short answer to the question of dryness is NO - they are not dry. The more more accurate answer is NO - they are not dry - and the dryness or moisture content is irrelevant, unless perhaps you are looking to buy today, cut or work and finish tomorrow, and sell the following day.
One can turn or carve something out of a burl and finish it the next day. But it will move as stresses that held it in its original shape are relieved, as moisture content decreases and the burl acclimates to local conditions, and when climatological conditions change from dry to humid or vice versa. Any violinist - like my wife - will tell you that even a 300+ year old Stradivarius will move, as will the kiln dried wood in your home. Eucalyptus burls are no different - the properties of wood and effect of humidity don't cease to exist because they are burls. So the same methods used to dry wood used in your home may be used to dry burls for use.
For some projects - a natural edge vase or power carving come to mind - a bit of movement may not be problematic. I've done both projects from start to finish (without kiln drying in between roughing and finishing). I find that the the inevitable raising of the grain on a power carving from a green burl is less bothersome the lower the sheen on the finish. That said, I will normally allow the rough carved burl to air dry for a lengthy period or dry/stress relieve it in my homemade kiln.
Eucalyptus burls I import may have been harvested as recently as 3-4 months to a year or more prior to taking delivery. They are very dense, so air drying would take forever. But it's not necessary, nor would I recommend waiting the standard 1 year per inch of thickness for a burl to air dry. Why? First, it would be subject to possible internal cracking. Second, a green burl will work more easily and may then be dried in a manner that will preclude cracking and minimize movement.
That is not to say that I do not recommend drying burls. I rough turn everything I make and then dry in a homemade kiln (what I call the "low and slow" method) or allow to air dry before finishing. Likewise, customers making knives, gun grips, call blanks pool cues, hybrid castings, etc., will want to make sure the burl is dry before finishing.
When cutting dimensional stock like cue blanks, scales, grips, veneer, movement will occur if they are not restrained in some manner. One can literally watch veneer bend immediately after cutting if not stacked or stickered with sufficient weight applied to restrain movement. To minimize movement, I restrain everything I cut by wrapping in stretch wrap, controlling the drying process. I leave the ends open or cut small holes to allow moisture to escape slowly.
My kiln is nothing more than an old refrigerator (obtained at a local dump free of charge) with most internals (other than shelving) and no longer necessary heavy components removed. I drilled 1/2" holes top, bottom and between the refrigerator/freezer sections for airflow, installed a small fan, thermometer and a 40W or 60W light bulb (depending on time of year) to maintain temperature ideally around 100 def F. Voila! Homemade kiln for about $25. And a very effective one. Of course, you can make something larger or smaller, more elaborate, with controls for maintaining temperature, but this is not rocket science. You can make as large or small, sophisticated or simplistic a setup as you'd like. What you can't do is eliminate the one variable that frustrates impatient people like most of us who work with wood . . . time.
Everyone would love to have their wood/burl dried overnight . . . preferably quicker. But that's not realistic. Or is it? Most everyone in woodturning I know has tried various methods of drying, whether in a microwave, which is labor intensive, size-limited and can burn the wood, or cooking in an oven. If I had to choose between the two, I'd choose the latter, though I don't like the associated risk of higher temperature in an oven (minimum temperature is generally 160F). But I have used the oven method (24 hours or more) successfully on a difficult project - an 18" Gummy Corrugata Burl winged bowl.
My normal method of drying remains the "low and slow" method because I believe it to be safest. I don't like putting my investment - either in time, money or passion - at unnecessary risk. When putting roughed projects in your kiln, there may be an initial waiting period before your initial project(s) is/are ready to finish working/casting/stabilizing/etc, but if you're constantly roughing, drying, finishing, it won't be long before you have a backlog of kiln-dried pieces.
To slow/control the drying process in your kiln, you may choose to seal your wood with an Anchor Seal or similar product, wrap with stretchwrap (like the knife blocks below), or do nothing at all. If you do use an Anchor Seal type product, be sure to leave an area untreated for moisture to escape. Personally, I rarely seal my pieces before kiln drying (though the hollow form in the slideshow below was indeed sealed), because I dislike Anchor Seal 2 (it takes far too long to dry) and because even if I see a piece open up (crack), I'm confident it'll close. The most egregious example of cracking I've observed was a small 10-11" Concinna Burl winged bowl I turned for a demo years ago. A crack developed on the wing during the first week of drying that opened up a good 3/16" - a significant crack for a small piece. By the time I was done drying the piece, the crack had closed completely. I finished the project (after a little over a month in my kiln) without doing anything to fill the the area where the crack originally developed. If I were to show you that piece today, you'd have a hard time finding any evidence of the original crack unless I mentioned it.
Whether you're drying a roughed woodturning, knife/gun blocks or scales for stabilizing, or natural edge blocks with the intent of casting hybrid blanks, the best advice I can give you is to plan for your finished product by making it larger than your desired end product and allowing for movement. There are, of course, ways to minimize movement. Just as I restrain the movement of cue blanks, reel seats and other dimensional stock I've cut by wrapping in stretch wrap, I might restrain the movement of scales or other thin stock in some manner, perhaps simply by putting some weight on them. Understand what is happening and why and you'll be better prepared to properly handle, dry and pro-actively protect your investment.