Before diving into this article, please have a read of the previous two prerequisite sections, Part 1 (Understanding the roast process….Heat vs. Mass) and Part 2 (What happens during the coffee roast process…).
So much like in the 1st part of this article, understanding heat vs mass, is critical to understanding how to properly roast. Roasting coffee is exactly like boiling a pot of water, except instead of a pot, we have a drum and instead of water, we have beans with water in them. If you understand the pot-water-boiling experiments in the 1st article, then you can understand easily what is happening inside the bean.
The key difference here, is that instead of us setting the heat, then waiting for the water to boil at “X” minutes, we are going to flip those two variables. This is the most critical part to roasting well. We are now with the coffee going to adjust the heat up to speed up the roast, or adjust the heat down to slow down the roast, just like increasing heat boils the water faster, vs. lowering the heat boils the water slower. THIS is the most critical part to understand.
Instead of targeting your temperature and waiting for the roast to finish (a common approach for some people) we are instead going to attempt to “fix” the time as your fixed variable and use temperature to speed up or slow down the roast (your adjustable variable) so that the roast finishes on time per the roast profile chart for your drum and volume. See this article for more on this subject.
So let’s look at a specific example:
Let’s use the following reference charts for our roast: ROAST PROFILES.
1. Find your drum size in the list
2. Select the finished roast volume you wish to roast.
3. Make note of the estimated 1st crack time and the 2nd crack time.
4. Make note of your suggested temperature. (Note that temeprature is relative to YOUR grill, see this article.)
5. During the roast, set the temperature to the suggested temperature to start and then adjust the temperature up or down while you roast to keep the roast progressing so that 1st crack occurs ON TIME for your drum and volume and ON TIME for 2nd crack. Keep in mind that things happen VERY quickly during the onset of 2nd crack. You can go from a medium roast to charcoal in 60 seconds after 2nd crack. During the lull between 1st and 2nd, be sure to have your gloves on and cooler running, and be on your toes from this point on.
6. If you’re new to roasting, pull the coffee when you hear 10 cracks in 10 seconds (10-in-10). This is a safe point to pull your coffee at with almost any coffee, and will all but guarantee happy customers and happy coffee drinkers, though there is always rooom for improvement in your roast profile. Sweet Marias is a great resource to perfect your profile for both the roast and the bean. If you would like to go a bit darker, then go to 10-in-10 and then add just 20 more seconds. At this point we will be at or around what is called “Rolling 2nd crack” where the beans are firing as fast as they can and could be equated to what sounds like machine gun fire, and is accompanied by tremendous smoke. Most coffee’s aren’t great past this point, so be very careful past this point as it’s likely in another 60 seconds your roast might be on fire.
That’s the basic concept. If you’re still having issues, give us a call and we can go through things on the phone, or do a roasting session together.