by Kyle Anderson, Baratza President and Chief Designer
I think the time has come to write a bit about the misconceptions and perceptions surrounding trace amounts of visible rust on steel burrs in coffee grinders.
A few important points need to be made: first, ingesting rust is not a health concern. "The National Institute of Occupational Safety and Health (NIOSH) indicates that rust is not toxic…... If eaten, the acid in the digestive processes will convert rust to iron needed for blood formation or excrete the excess." Second, the existence of rust is in no way evidence of a low quality grinder or burrs. Commercial grade steel burrs are made from high-carbon steel, NOT stainless steel as is often mis-stated. Carbon steel will rust if exposed to even slight humidity if not "seasoned" or protected with some sort of oil/lubricant. Rust is virtually non existent in coffee grinders that have had a few pounds of coffee put through them, even after periods of non-use. This is a result of "seasoning of the burrs" similar to cast iron cookware.
In recent talks with some commercial coffee grinder manufacturers, they admitted they often have rust present on their new grinder burrs, but most of these are never taken apart by the users (if ever) until the grinder has ground hundreds (or more) pounds of coffee so they do not have perception issues. Baratza grinders (by design) are made to allow quick burr removal by the end user. This in turn allows users to inspect the burrs on their new grinders even before they put coffee through it. Heck, we even made a tool to help you remove the burrs! The trace amounts of surface rust that are present on some of our burrs will quickly disappear after just a few pounds of use. By way of analogy, if you walk through a parking lot with high quality automobiles there, and look at the disc brake rotor, you will very often see the entire rotor coated with surface rust. This is NOT cause for concern, as a simple drive around the block removes all of the rust. No one takes their brand new Porsche (or Lexus) back to the dealer to get brakes replaced (or the car replaced!) because of rust on the brake rotor.
So, yes, you may find some rust when you receive your burrs. Yes, this is normal and it will not harm you, nor does it make for an inferior burr. Please enjoy your coffee!