Info About Our Roaster
There are a lot of different roasters on the market. There are two primary styles of roasters: air roasters and drum roasters. I am going to skip right past talking about air roasters because I think they are lame, and I don't want to waste your time. I spent a year working at a company with an air roaster held together by ductape and gum. As Dom tells Brian in The Fast and The Furious about the two years he spent in Lompoc prison, "I'll die before I go back"
Drum roasters kind of look like a popcorn popper on steroids. Green coffee is dropped in from a hopper on top of the machine and shoots into the drum. The drum is then heated by a heat source, in the case of our roaster a set of infrared burners. There's also a plurality of drum roasters out there too. Some drum roasters have gas burners with exposed flames. Some drum roasters have double walled drums to insulate the heat while protecting the coffee from being scorched. Lot's of info, but for this email I mostly want to talk about our machine
Most roasting machines use an atmospheric heat source where the flame is out and away from the drum. Atmospheric heat sourced roasters generally have trouble distributing heat evenly around the drum. To solve this problem manufacturers began encasing the drum that the coffee spins around in with another drum to insulate the heat. These double drum roasters are great and stable but they also take a ton of gas to power. Stephan Diedrich founded Diedrich Manufacturing in 1980 with the idea of developing a coffee roaster with a more targeted heat source.
Diedrich developed the IR-12 (Infrared - 12 KIlo) in 1981. This machine utilizes infrared heaters and fans creating a combination of heat, airflow, and timing that results in an optimum environment for every varietal of coffee bean.
A lot of elements go into how your roaster functions, but gas pressure is key. The number of bars of gas pressure you can get into your building, how long the gas line is, the size of the gas line, and what else draws from it all determine the amount of gas pressure going into your machine. Because of this, not all roasters work exactly the same way in every space. Sometimes, even when I am roasting here at our warehouse, the heater kicks on and draws energy from the gas line. Suddenly my gas pressure to the machine is way off.
It’s a lot like in the opening scene of The Fast and The Furious where Brian is driving his car in the parking lot outside of Dodger Stadium. It has all of the potential to be a super fast car, but something is holding him back - his car tops out at 140 mph and Brian is pissed. Our gas pressure may read out at a certain amount according to the building's code, but once the gas lines are put in and dragged across the length of the warehouse we can only get a fraction of its potential.
Brian Spilner: "My car topped out at 140 miles per hour this morning--
Harry: "Amateurs don't use Nitros Oxide,
I've seen the way you drive, you've got a heavy foot you will blow yourself to pieces"
Batch Size, energy, coffee density
Now when the machine says that it has a 12 Kilo drum, this doesn't actually mean you can toss 12 kilograms of coffee into it. Roasters don't work as a direct heat source like a grill or an oven. When you toss something in your oven the heat coils are directly cooking what ever is on your sheet tray. In a coffee roaster the heat is outside of the drum, and you are taking that heat and transferring it from the drum to your coffee beans. We like to think of heat as energy in coffee roasting.
All of the technology that Diedrich puts in to their roaster allows it to maximize potential while putting up with any sort of physical limitation your building has. It's kind of like in The Fast and The Furious where Brian and Dom raced for the pink slip to Brian's Mitsubishi, only to have Johnny Tran's gang blow it up over some turf war stuff that they don't really flesh out very well in the story. Brian still owes Dom a car and brings him what looks like a toasted out hunk of crap. BUT - when Dom and his crew pop the hood of the car Brian brings in, they realize its true potential.
When you are preparing the drum for a roast, you apply heat to the drum until the drum reaches a specific temperature and then stabilizes. More specifically, adding heat to the roaster means we are more adding more energy to the drum. When green coffee gets dropped into the drum at the beginning of the roast we are transferring that energy from the drum into the beans.
This is where that conversation about gas pressure circles back around. We have a max gas pressure that we can apply to the roaster. This gas setting most likely won't provide enough energy for the roaster to run at 100% capacity. Most roasters run at 50-70% capacity, so rather than being able to roast a 12 kilo batch, we realistically can roast a 6-8.4 kilo batch.
When Ja Rule's character Edwin says at the first racing scene in The Fast and The Furious, "It's not how you stand next to your car, it's how you race your car," he's basically saying "Depending on the gas pressure in your building, only so much energy from the drum can be transferred to the inside of the bean."
This heat transfer speaks to another element of roasting your coffee, and more specifically to your coffee's density. If your coffee is particularly dense you will need more heat/energy to pass from the drum into your coffee. This means that as we are seasoning the drum and warming up the roaster, we need to consider the density of the coffee we are roasting. If it is a particularly dense coffee we will want to start with a higher "drop temperature." If the coffee is less dense or "soft," we will start at a lower drop temperature because we know it will take on heat more easily.