Choosing the right coffee charge temperature involves balancing batch size, bean density, and roast level to hit a turning point around 45–90 seconds.
It's the stored energy in the roaster that kicks things off.
A higher charge (>200C) suits denser beans,
while lower charges (roughly 160C-180C) prevent scorching of low-altitude beans.
Decaf would call for a noticably larger batch size or lower charge temp.
The average charge temperature for a Hottop roaster typically ranges from 300°F to 375°F (149-190c) as measured by the Bean Temperature (BT) probe. While the manufacturer's automatic default is low (around 167°F or 75°C), experienced users often charge higher for better energy management, often around 350°F
Key Factors for Setting Charge Temperature:
+Bean Density:
High-density/high-altitude beans generally require a higher charge temperature
to penetrate the bean core.
Lower density beans are prone to more roast defects (you need to be more gentle with the heat).
+Bean size & shape
bigger beans take longer to roast.
round or small beans move differently in the roaster - roasting more evenly and quickly.
+ moisture content
Beans with a higher moisture content take longer to dry.
+Type of bean processing.
Natural or honey processed usually have more sugars on the outside, so roast faster or scorch
if you are not careful.
Washed coffees tend to roast more evenly.
+Batch Size: Larger batches necessitate a higher charge temperature to provide
enough energy to the larger mass.
+Roast Level: Light roasts, which need a faster, shorter development time, often benefit
from a higher charge.
Espresso or darker roasts can start at a slightly lower charge to manage the heat needed
for a longer roast.
+Roaster Environment: Ensure the machine is properly heat-soaked, usually with
the environment temperature significantly higher than the drum temperature.
+Turning Point Indicator: The Turning Point (TP) is when the bean temperature
rises after being cooled by the charge
TP too fast (<45s): Charge temperature is too high.
TP too slow (>90s): Charge temperature is too low.
TP just right = 60 s (general rule of thumb)
Fine-Tuning Tips:
If your coffee tastes like it has "roastiness" or you observe scorching/tipping, decrease your charge temperature.
If your roast takes too long to dry (before the yellowing stage), increase the charge.
Naturals often perform better at a slightly lower charge to avoid over-roasting the exterior, while washed coffees can handle more heat.
Exhaust temperature
This is very impt as it indicates how much energy you have in the roaster & can be used to soak the beans. It will tell you if you have enough momentium in the roaster.
The Exhaust temp should be higher than the bean temp.
If the exhaust temp if aways higher than the bean temp then you will always have a positive ROR.
Towards the end of the roast, the two temps will meet .
The Exhaust temp is influenced by the drum speed and energy changes.
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HotTop roaster settings
+Optimal Range: 300°F–350°F (149°C–177°C) is commonly cited for a good balance,
avoiding scorching while ensuring enough energy for the roast.
+Higher Density Beans: Use higher charge temperatures (approx. 375°F or 190°C) to
ensure enough energy enters the bean.
+Lower Density/Softer Beans: Use lower charge temperatures (approx. 325°F or 163°C)
to avoid scorching.
+Batch Size: For a 250g charge, 350°F is a common starting point. If reducing batch size
to 175g, some users increase charge temperatures to 390°F–410°F to maintain heat.
+Roast Style: Espresso roasts often use higher charge temperatures for more heat,
while lighter filter roasts might use slightly lower, faster-acting profiles
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