This video is a very basic introduction to the roaster. Without too much details we go over the basic setup of the roaster. This is a good start if you just received your ROEST and wants to start roasting as soon as possible.
How to ROEST
In this article we will go over how to roast on the ROEST Sample Roaster.
Compared to other sample roasters on the market ROEST is a combination of the two most used technologies; small hot air roaster and conventional open drums.
The drum (black line) itself is fixed while paddles (white lines) agitate the coffee. Heated air (red arrows) passes through openings in the drum wall and moves diagonally across the roasting chamber creating a uniform heat distribution throughout the entire length of the drum. The coffee moves almost like a constant breaking wave, falling over the heated air. For each rotation, the coffee has time to absorb the applied heat.
We will in the following go over the most important features that can be adjusted on ROEST.
Temperature and power
The roasting temperature or environment temperature (ET) is the primary variable for adjusting a roast. It is measured in the upper mid-section of the drum. This temperature response very rapidly to power changes of the heating element, so if you take manual control of the roast, start with only 5-10% increments and see how it affects the temperature.
To simplify a bit we can say there are two ways of controlling the machine; power or temperature. When controlling the power, any changes made in the power percentage is directly changing the power input to the heating elements. When you are controlling the temperature, the machine automatically adjusts the power input to achieve the correct temperature.
For consistency and ease of use, temperature based profiles (ET profiles) is your best choice. To experiment and learn the behaviors of a new coffee, manual roasting is ideal.
If you want to adjust the total roast time, start with adjusting the temperature or power based on your earlier roasts.
Ending a roast
There are three ways to end a roast.
Manually by opening the discharge (drop) handle.
Pre-defining an end time in the profile.
Registering “first crack” on the touchscreen and have the pre-set timer automatically discharge the coffee at a given time after first crack.
The workflow on ROEST is designed to perfectly develop each coffee and that’s why option number three is our favourite. Only then can you adapt your profile to each coffee and make sure you fully develop it. Combine this with up to five profiles stored in the machine, roasting and fully developing different coffees has never been easier! And of course; in time, sensors will take over the detection of first crack (we already have a beta-version up and running).
In temperature-based profiles; the higher the airflow, the more energy is used. Higher airflow will have an impact on the roasting time. However, the effect is not so significant as you might have experienced with traditional open drum roasters. In order to adjust the total roasting time, we suggest adjusting the temperature or power. We have roasted great coffee on both low and high airflow. It depends on the profile overall – and of course – the coffee.
Changing the RPM of the mechanical arms agitation the coffee will have a much larger impact on the roast then changes made to the airflow. With higher RPM the coffee is “thrown” into the heated air and the total bean mass density in the chamber is significantly lower. The yellow arrow represents the bean mass in the illustration. With higher RPM the coffee will be exposed to the heated air in a more efficient way, but it will at the same time impact the precisions of the bean temperature sensor since the density of the bean mass is lower. But to summarize; higher RPM equals a faster roast.
On the other hand, a lower RPM gives a better bean temperature reading. We utilize this knowledge in our profile design. We start with a low RPM to let the coffee utilize any conduction heat in the drum. We then increase the RPM to increase the efficiency, and to compensate for the weight loss and volume expansion of the beans we slowly reduce the RPM towards the end of the roast.
You can see this in the profile below. Motor RPM is the red line. We lower the rpm in the start to take up all the heat from the drum. We then let it gradually go up to a high speed before we let it go down to 55 RPM towards first crack.
For temperature profiles the charge temperature is given by the first second of the profile. Depending on the profile it can be beneficial to have a higher starting temperature than the profile itself. This can be achieved by setting a higher temperature for the first second (see illustration) and let it drop down in temperature. It’s not necessary but will help the roaster to stabilize the temperature in the first minute of the roast.
For power profiles the charge temperature is adjusted in profile settings from the touchscreen.
ROEST is equipped with a trier for sampling during a roast. The trier is engineered with a cylindrical end so that it can be used without letting too much cold air into the roasting chamber. This is achieved by blocking the trier-hole with the end of the trier. If a dip in ET is measured than too much cold air is let in.
We therefore recommend using power profiles if you want to use the trier extensively. The bean temperature and the beans itself is not very influenced by using the trier, but don’t keep trier out for too long.
Back to Back roasting
The combination of our patented roasting chamber and the separated cooling fan makes ROEST the most efficient sample roaster on the market. Roasting 1,2kg of coffee in one hour is not a problem. A new batch can be started immediately after the last. For optimal control and consistency it’s recommended to wait a few more seconds to let the machine reach your profiles starting temperature.