Material
Talc
Answer in brief
Talc is the material that makes engineers respect particle shape.
The platelets interlock, so the powder arches over large openings, and the same platelets trap air, so it floods through a valve minutes later.
- Size outlets generously and add a mechanical discharge aid from the start.
- Deaerate before feeding, or accept that dosing accuracy will drift.
- Enclose transfers, because the dust travels everywhere.
Reviewed October 21, 2026 · Updated October 21, 2026
Handling challenges
Talc looks harmless and behaves like one of the most difficult powders in industrial use.
Why the shape matters
Platy particles pack together with a high contact area, which gives strong interparticle friction and a flow function well into the cohesive range.
The same shape holds air between plates, so freshly conveyed talc has a bulk density far below the settled value and flows uncontrollably.
Silo discharge
- Large outlets sized from measured flow properties, not from experience with other minerals.
- Mass flow geometry with low wall friction liners.
- Mechanical discharge aids such as bin activators or screw dischargers.
Aeration pads should be used sparingly, since over-aeration converts an arching problem into a flooding problem.
Feeding
Loss-in-weight feeding with an agitated hopper, a deaeration volume and vibration isolation delivers a usable rate.
Volumetric feeding of talc is unreliable because the bulk density is not a constant.
Dust and exposure
Talc dust is respirable and persistent, and cosmetic grades carry additional purity scrutiny.
Closed transfer, contained bag emptying and well-maintained extraction are the practical controls.
What to establish before buying equipment
- Flow function and wall friction on the delivered grade.
- Aerated and settled bulk density, which differ widely.
- Deaeration time available before the feeder.
- Exposure limit applicable to the grade and the plant.
Material behavior
- Flowability
- Very poor, with flooding after aeration
- Abrasiveness
- Low
- Cohesiveness
- Very high
- Moisture behavior
- Low moisture uptake, but moisture worsens bridging
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