A question I get frequently is, “What is infrared?” The impression is that it is something like Ming the Merciless’ Death Ray! One “roaster” ordered me to accept that a Diedrich Roaster roasts beans from the inside-out. I was sharing a cab with him at the time and it was a little scary, so I didn’t try to change his mind. If someone tries to tell you this, watch out.

Although “roasting” from the inside out is physically impossible with radiant heat and would be a really crappy way to roast anyway, it does bring out the concern that infrared heat sounds scary and dangerous; ultra-secret scientific woowoo. So, bwahahahaha weak earth creatures, prepare to meet your doom!

“That is nonsense,” you say. What is it really? We use gas, just like, well … everyone, only we contain the flame into a long box, which is as wide as the drum. The top of the box is closed with ceramic tile. This tile is superheated by the gas flame in the box and gets so hot, the heat radiating off the tiles is invisible; it is radiating in the infrared spectrum. No blue and yellow flames here! (Full of contaminants) Invisible waves of infrared light waves surround the drum and heat exchangers. When they hit the metal, they heat the metal in a complicated atomic rave. The rest is roasting coffee.

The thing that is different about our burners compared to all the blue flame roasters is that when you look inside our roaster you see the pure wide rectangles of brilliant orange/red tiles extending the entire length of the drum. Consistent, clean, dependable heat directly transferring to the drum and heat exchangers. Almost all of the combustion is taking place behind those beautiful ceramic tiles. Our infrared burners produce an even band of heat that assures there are no “hot spots” or cool temperature bands that can screw up your roast.

This is just like the ceramic top stove-tops many of us have at home – fast, dependable, controllable, and very powerful.

So don’t worry about infrared! It is completely safe, even to weak earth creatures. And, when it comes to roasting coffee, it is the best … period.



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Could we be more confusing? What is the difference between an IR roaster and a CR roaster? I can’t count the number of times I have been asked this.

This is a classic example of “Why do we do that?” Diedrich has been building roasters for 40 years and over time we have grown, innovated, and improved. A Diedrich roaster today is a lot more sophisticated than the ones first built in Steve’s dad’s garage. So the reason we named the roasters IR and CR is a little lost in history.

As far as I can tell, Steve knew he wanted to use infrared burners on his specialty coffee roasters. He knew that they used less gas to produce the same BTU’s and produced a clean heat evenly across the drum. He also knew that using less gas meant he produced far fewer dangerous chemicals that would get drawn through the beans. Steve was all about producing the cleanest and freshest cup possible and that discipline drives our designs today.

Then along came a customer who wanted a BIG roaster. Steve wasn’t so sure he could source infrared burners that would produce enough BTU’s to support a big load of coffee so he built his first CRs (Commercial Roaster) with an atmospheric burner. The same flame throwers that are in our competitors’ roasters.

Through testing however, Steve discovered that he was wrong! He discovered that he could design larger burners that produced a lot more BTU’s using a lot less gas. Soon all of our roasters, big and small, used infrared burners.

The legacy of this though is that our 1 through 12 kilo roasters are called IR (infrared) and the 25 through 280k roasters are called CR (commercial). But they are all infrared!
This has produced a lot of confusion and rumors out there. To make in worse for the past couple of years we started calling IRs “In-Store Roasters” which doesn’t come close to describing all the ways folks use the IRs.

So to clear things up…

All our roasters use infrared technology to roast coffee
Infrared is the cleanest and most fuel efficient source of roasting heat, period!
Infrared at full gas far exceeds the full BTU output of comparable flamethrower roasters
Reduced combustion gases in the drum produce a cleaner cup
I personally would like to give our roasters real names; I think the IR-5 should be called Charlie. I suppose it is a good thing that it isn’t up to me.



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The Essentials of Coffee Roasting : Have a good Plan

I have been asked several times, “What is the single most important piece of advice you would give a new roaster?” The answer is easy but the practice may not be: always have a plan before you start roasting.

On the surface this seems easy enough.

Your plan, however, should be more than, “make green into brown.” It should involve having a purpose for your roast and an expected result.
An example might be: Roast 5 ARRIVAL samples to a cupping standard for evaluation tomorrow morning. Now you know what you are roasting, why you are doing it and an expected outcome of Agtron 58 whole bean of 58 +/- 1 in 8-12 minutes. This is a simple, well thought out example.

Others plans might be a little more complicated. Here are some plans you might want to consider. You can take these as a starting point for your roasting and make them as detailed as you want.

If you have been roasting for a while you probably have a set of ‘common’ profiles you use. If not, build some thereby creating a small library of starting profiles. This will save many hours and lots of coffee in the future while making your outcomes more precise and consistent.

A good plan well executed saves time, money, and frustration while increasing quality and consistency.

Rocky Rhodes