Alumina Desciccant: Regeneration Timeline

Having accumulated a suspiciously precise 700 g of activated alumina desiccant from the PolyDryer filament boxes, I poured it into the same cast-iron pan on the induction cooktop:

Based on the results from last time, I set the temperature to the cooktop’s maximum 460 °F and, bother fiddling with condensing the moisture on a lid, and let it cook.

Weighing the beads (about) once an hour:

• Start: 700 g
• 1 hr: 678 g
• 2 hr: 666 g
• 3 hr: 661 g

The 39 g water loss is 5.6% of the wet weight and 5.9% of the dry weight, which is roughly the amount absorbed by both silica gel and alumina after a month or so in the filament boxes.

During those hours the surface temperature rose from 73 F to 190 °F, although the exact number depends on exactly where the IR thermometer was staring. Stirring the beads to get an average temperature might be more convincing, but not by much.

Exactly how dry the beads become after three hours remains unknown, but the temperature increase suggests most of the water has gone elsewhere.

Cooling the beads in a covered bowl and pouring them into a jug produced a total weight of 767 g, which settled at 770 g over the course of two days; the jug seems reasonably vapor-tight.

Alumina beads seem much less prone to damage by overheating than silica gel beads and have similar performance in the boxes, which makes them a strong contender for the next round.