How to Roast Coffee at Home, Chapter 5: Same coffee bean, same roast profile, different temperature readings..what the heck?

A couple days ago, we roasted the same Java Bondowoso beans we featured in Chapter 1. Our goal was simple: roast the same green coffee bean with four different profiles, and see which one tasted best.

However, we noticed something kinda weird. 

Despite roasting the same batch size at the same temperature we used in Chapter 1, this time first crack started at 403 F instead of at 388 F like last time. What the heck is going on?

Most likely, our temperature probe was in a slightly different place. If you ever use an instant-read thermometer when grilling a steak, you'll be familiar with this principle. Temperature can vary several degrees per millimeter, so the temperature near the surface of the meat is generally hotter than the temperature of the "core."

Because we MacGyver'd the probe into the coffee roaster using regular tools in the backyard, this  roast-to-roast variability is something we'll have to live with for the time being. 

We'll let you know if we conjure up a better mousetrap...or if we win the lottery and can pay an industrial engineer to trick out our roaster with laboratory-level instruments.

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