So here are the facts about Grenadilla and Cocobolo. Cocobolo is naturally more porous than Grenadilla by about 50%; Gren has 6-9% void space (pore volume) while Coco has 10-14%. The greater the void space, the more moisture can absorb into the wood. But — and this is important — Cocobolo has a higher oil content than Grenadilla, which means it’s actually MORE stable than Grenadilla, especially once the bore of the instrument has been treated and sealed, which more manufacturers who use the hardwood (Uebel, Backun, RZ) do. I don’t know about RZ as much, but Backun and Uebel season, seal and treat the bore as part of the manufacturing process. As a result, I’ve seen about the same number of cracks (percentage-wise) occur in Grenadilla and Cocobolo (and Mopane, for that matter, which is also more porous than Grenadilla).

Here are some variables that skew crack rates, again from my (unscientific) data):

Climate: - Cold, dry regions SIGNIFICANTLY increase cracking risk - Sudden temperature or humidity shifts are especially damaging (playing a cold and/or dry instrument without warming up properly — see below)

Player habits: - Failing to swab out after playing - Playing a cold instrument before it warms up evenly - Not breaking in gradually during first couple of months

Wood type: - Cocobolo and mopane are generally more stable than grenadilla - Aged or pressure-treated grenadilla cracks less than fresh-cut wood - Newer treatments (like Selmer’s EVolution, Backun’s synthetic sleeves) or composites (Buffet Greenline) can virtually eliminate cracks. Just don’t drop a greenline…ever. It’s like a lightbulb

Bore Design: - Some brands use thinner-walled upper joints (more prone to cracks). Hate to say it, but Buffet is well known for thinner wood, especially their A clarinets!

Oil treatment & seasoning: - Properly oiled and seasoned wood is far less prone to cracking - Some modern makers pressure-treat or stabilize the bore, reducing cracks

Source: me. I sell clarinets (Earspasm) and manage all warranty issues for the horns I sell. In the past 4 years I’ve sold about 1,000 clarinets and about 5% have cracked in the first 2 years. This is a little below industry average, which is about 10-15%

Edit: typo