12
The roast used for the graph was done by programming the KN-8828B-2K for maximum time (25:00)
and maximum temperature (428 F.). Using these parameters, start the roast as instructed on page 17. Many
users have experimented with the temperature at which they add the beans to the roaster. In this roast the
beans were dropped in at an the “Beep” signal at a temperature of approximately 167 F. on the display
(
1
), as the
red
line indicates. You might try waiting until the display shows 200 to 225 F. and see how that
works for you. The amount of beans used also will affect the roast. To begin with we recommend using
250 grams. You may experiment later with 225 to 235 grams to see how this affects the roast, and most
importantly, the flavor. Smaller amounts of beans will speed the roast.
Remember that coffee is a food product.
The most important factor is
HOW THE COFFEE TASTES TO YOU
!!
After you add the beans to the roaster they begin to absorb heat energy, transferred to them by con-
vection (exposure to the hot air), conduction (through the hot metal of the drum), and to a lesser degree
radiation (radiant energy from the heating element).
When the roaster hits about 200F., turn the fan to 25% or 50% (
2
) for thirty seconds to one minute.
This will help clear moisture out of the roaster that comes from the beans. When the display temperature
reaches around 280 F. (
3
) the beans are about to enter the important drying phase. Watch through the
observation window on the front of the roaster and you will see the beans begin to change to a green color
as shown on page 13. Moisture in the beans is being removed and you might begin to notice a pleasant,
grassy smell somewhat reminiscent of a freshly mown lawn.
At this time it is important to allow the beans to lose their moisture throughout their structure. This
insures that the entire bean roasts evenly as the temperature rises later in the roast. Rushing through the
drying phase may roast the outer areas of the beans sufficiently, and the beans can look fine, but the inner
portions on the bean can be left at a lesser roast level causing unpleasant tastes in the cup.
To control the drying phase, at around 259F. set the fan to 25% (
4
) and at around 280 F., turn the heat-
ing element to about 70 or 80% (
5
). Once again, the fan will help clear humidity from the roaster which is
coming from the moisture inside the beans. The goal here is slow the increase in temperature in the roaster
until it reaches around 300F. which marks the end of this phase. This allows the temperature of the inside
of the beans to “catch up” with the temperature of the outer surface.
Note that when the heating element was turned down (
5
), it took some time for the temperature in
the roasting chamber to react to that event (
6
). As mentioned earlier in this section, this is normal for an
electrical heating element. Learning how to predict this is part of the learning process and being aware of
this will help you get the most out of your KN-8828B-2K when roasting manually.
Keep in mind that while attempting to control the temperature it is better to allow it to rise slowly
than to drop. If the temperature in the beans is allowed to drop during the roast it can lead to undesirable
results. Keeping the display temperature rising slowly during the drying phase will assure that the beans
are safe. As you get more experienced in use of the controls of the KN-8828B-2K you will be able to more
precisely control the temperature.
All this time you should keep an eye on the beans. They will go from light green to an amazing bright
green color. This marks the height of the drying phase. The bright green will begin to fade and they will
begin to turn tan in color. Around the time that the green color is beginning to fade it indicates that the
beans themselves are in the vicinity of 300 F. (
7
). This is the time to turn the heating element up to 100%
again (
8
). Shortly after that the smoke will increase and it is time to turn up the fan (
9
). Over the next four
minutes or so the temperature of the beans will continue to rise and the tan color begins to darken towards
cinnamon and brown. Watch carefully. At an indicated display temperature of around 360 F., the display
temperature will be showing the bean temperature as their temperature plots cross. This is a time when
things are happening quickly.
At around 370-375 F. an adjustment should be made. To keep the beans from going through the end of
the roast too quickly, it is time to turn the heating element down (
10
). Notice that even though the graph’s
green
line (environmental temperature), begins to level off (
11
), the bean temperature is still rising (
12
)!