The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

The New Hotness

  • PolyDryer Humidity: Alumina vs. PETG-CF

    A pair of PolyDryer boxes has been holding black and gray PETG-CF for a while:

    PolyDryer - PETG-CF - 32 pctRH Black 31 pctRF Gray
    PolyDryer – PETG-CF – 32 pctRH Black 31 pctRF Gray

    A few days ago I slipped humidity indicator cards into the boxes:

    The black PETG-CF card suggests 30 to 40 %RH:

    PolyDryer - PETG-CF - 32 pctRH Black test card
    PolyDryer – PETG-CF – 32 pctRH Black test card

    Yes, I dropped that card into the box upside-down.

    The gray PETG-CF card shows similar results:

    PolyDryer - PETG-CF - 31 pctRF Gray test card
    PolyDryer – PETG-CF – 31 pctRF Gray test card

    The desiccant in the black PETG-CF box weighed 80.9 g, a gain of 5.9 g = 10.8%. The chart suggests that corresponds to 35 to 40 %RH:

    Desiccant adsorption vs humidity
    Desiccant adsorption vs humidity

    The gray PETG-CF box had 102.0 g of desiccant. I apparently loaded 25 g in the meter container and 70 g in seven tea bags, but I don’t trust those numbers enough to go any further.

    Unlike the black PETG box mismatch, these black PETG-CF numbers seem plausible. The results may depend on allowing far more time for the filament + air to equilibrate with the desiccant tucked in its containers than the days I’ve been giving it.