If roasting is driven by heat, does it matter how that heat is delivered?
 

Charcoal and electric roasting follow different paths in how heat enters the leaf. Roasting works on a leaf that already holds structure. The mao cha (unfinished tea) has passed through earlier steps. A direction exists, but it has not settled. Heat does not create from nothing. It moves what is already present toward a certain state. How heat enters the leaf, and how the surrounding environment behaves, shapes the result.

Electric Roasting
Electric roasting works through hot air. Heated air moves through the chamber and contacts the surface of the leaves. Heat concentrates on the outer layer. Moisture is drawn out. The surface tightens and dries, while the interior lags behind in both temperature and moisture movement. If the time is short, the inside remains close to its earlier state. If extended, the surface continues to lose moisture, and aromatic compounds are carried away with the airflow.

Charcoal Roasting
Charcoal roasting follows a different path. Heat rises from below and enters by radiation. There is a layer between the fire and the leaves. The chamber does not carry strong air movement. Heat moves more slowly, but with less separation between outer and inner layers. Moisture shifts at a slower pace. Transformations take place across the leaf rather than at the surface.

The Roasting Environment
The air environment also differs. Hot-air roasting requires continuous intake and exhaust. Air is constantly replaced. Oxygen remains present throughout the process. In charcoal roasting, combustion consumes oxygen. The environment within the chamber tightens. Changes proceed at a slower pace.

Handling the Roast
The way each method is handled follows from this. Charcoal roasting requires movement and adjustment. Leaves are turned. Airflow is managed. Heat is watched and corrected. The process depends on experience and does not follow fixed parameters. Electric roasting relies on chamber design and control systems. Temperature and airflow are set. Leaves are exposed to a more uniform condition.

Combining Both Approaches
In some structures, both approaches are placed together. A charcoal source is introduced into a hot-air system. The charcoal does not provide the primary heat. It contributes a layer of smoke and wood aroma that settles on the surface of the leaves. Heat still arrives through moving air. The outer impression shifts. The internal path remains unchanged.

Further Reading:

• Oolong Tea Roasting – Part 1 : Oolong Tea Roasting Levels : Temperature, Time and Flavor Structure
• Oolong Tea Roasting – Part 2 : Humidity and Airflow in Tea Roasting: Moisture Movement and Internal Balance