I received an especially good question from a customer last week about his destoner:

"I’ve caught a stone last week and a stick a while back in my batch of coffee after using the destoner. See picture of last weeks stone found. I’m really nervous using this machine. The coffees I buy don’t have a tonne of stones. I bought this destoner to catch the one or two that may be present in a bag. Please advise."

I responded:

All destoners work on differential density. They only remove stuff heavier than coffee seeds.

Your picture shows a cement chip, not a stone. Cement chips come from drying patios. They are the same size, color and density as coffee seeds. They often slip past optical sorters and destoners and pass through grinders harmlessly.

Similarly, no destoner will pick up wood slivers or twigs small enough to act like coffee seeds. They'll have to be removed manually. I've never encountered a twig, but I'm guessing anything that wasn't caught in the destoner would pass through a grinder harmlessly.

I understand your concerns, but this isn't anything to be concerned about. If it's a source of anxiety, run the seeds through twice. Beyond that, letting your wholesale customers know that you are running all of your roasted coffee through a destoner for their protection serves a valuable prophylactic purpose. All it takes is one goofy ticked off counter kid to ruin everybody's day by tossing a stone into the grinder.

You'll still end up paying for a new set of burrs, but the fact of the destoner makes it less likely you'll lose the account.

Free advice.