Like visco, igniter cord burns with an external, visible flame.

This may give either a visible flame or an audible sound.

A methanol-based fire burns invisibly, unlike gasoline, which burns with a visible flame.

When this substance was packed inside hollow bamboo stems or paper tubes and lit on fire, the explosions were louder and produced visible flames.

The fire produced no visible flames but thick, acrid smoke and fumes filled the area.