G Pen Pro

The Pro drives hot air up through holes in the floor of its white ceramic chamber, so resin builds first around those holes and along the lip where the mouthpiece seats. Grenco's chamber only holds about 0.25 grams and wants a fine grind tamped down firmly, which is exactly the packing that pushes dust into the airway and the mouthpiece screen.

1. Empty it while it is warm: Grenco's instruction for the Pro is to pull the mouthpiece and tip out the spent material as soon as you finish. Nothing unscrews here, so pinch the mouthpiece and lift it upwards and slightly to the side.

2. Brush the chamber cold: Let the unit cool, then sweep the ceramic with the small cleaning brush that ships with the Pro. Clearing the air holes in the floor matters most, because a blocked floor starves the convection.

3. Break the mouthpiece down: The silicone rubber sleeve slides off the outside. The tubular filter section pulls out of the bottom, and the metal screen inside it lifts free with tweezers.

4. Soak only the hard parts: Grenco allows the mouthpiece to sit in isopropyl, followed by a warm water rinse and an air dry, and the loose metal screen can be soaked and then scrubbed with a cloth. Keep the silicone sleeve out of the alcohol. Isopropyl that lingers on silicone and plastic degrades them, so wipe the sleeve down and use a silicone safe cleaner on it instead.

5. Swab the chamber, never flood it: A cotton bud lightly dampened with isopropyl takes the film off the ceramic walls. The aluminium body does not open, and the heater and sealed cell sit directly beneath the chamber, so anything that runs past the air holes has nowhere useful to go.

6. Dry before reassembly: Grenco's routine ends at an air dry rather than a burn off cycle, so give the screen and filter tube time rather than reheating them wet. Refit the mouthpiece with its air hole facing away from the control button.

Brushing the chamber after each session keeps this quick; a full strip of the mouthpiece every week or two suits most users. The 2200mAh battery is internal and not user replaceable, taking one to three hours to fill and giving roughly twelve four minute activations, so keep the micro USB port at the base clear of pocket lint and charge before the LEDs flash empty rather than storing it flat. Grenco sold the Pro's replacement mouthpiece as a set with a fresh silicone sleeve, which is the answer to a torn sleeve or a screen you cannot get clean, though spares are scarce now the model is retired.