Valve size
A larger valve opening matches the spout diameter of high-output filling machines and cuts blow-back around the nozzle, which is where most product loss and dust comes from.
Application · Chemicals & Minerals
Bags for iron oxide, pigment and fine chemical powders
Multi-wall paper sacks with large valves and perforated plies for 20–25 kg fills, built to keep fine, staining powders inside the bag and out of your warehouse air.
What We Supply
Engineered for powders that stain, drift and cake
Pigment powders are fine, high value and hard to clean up once they escape. The bag has to fill quickly, seal tightly and stay sealed through container handling — that is a structural question, not a printing one.
- Multi-ply kraft structures with a large valve opening
- Perforated plies for fast de-aeration during filling
- Optional PE inner liner for moisture protection
- Reinforced bottom for pallet stacking and drop loads
- Printing of product name, batch panel and warning marks
Specifications
Common pigment and chemical bag structures
Structures we build regularly for oxide pigments and comparable fine powders. Final dimensions follow your fill weight and product density.
| Structure | Valve | Fill weight | Best for |
|---|---|---|---|
| 3-ply kraft, 80 gsm | Large paper valve | 25 kg | Iron oxide red, yellow and black pigments |
| 3-ply kraft + PE liner | Large paper valve | 20–25 kg | Moisture-sensitive oxides and additives |
| Multi-ply kraft, perforated | Inner or outer valve | 20–25 kg | Fast filling lines with dust extraction |
| Woven laminate + thickened PE liner | Sewn or valved bottom | 30–40 kg | Mullite sand, zircon sand and heavy minerals |
Design Choices
What we adjust for fine powders
Perforation
Fine powders displace a lot of air. Perforated plies let it escape so the bag settles flat instead of ballooning on the pallet.
Seam integrity
Staining powders find every weak seam. We add inner and outer reinforcement at the bottom and check the seals in process, not only at final inspection.
FAQ
Pigment and chemical bag questions
What structure for 25 kg iron oxide?
A 3-ply kraft bag with a large valve is the usual choice, with perforated plies for fast de-aeration. Add a PE liner when the pigment has to stay completely dry.
Why a large valve?
Fine pigments fill fast and generate airborne dust. A large valve shortens filling time, reduces blow-back around the spout and helps the bag sit flat afterwards.
Do pigment bags need a PE liner?
If the product is moisture sensitive or the route is humid, a PE liner of 0.04–0.07 mm prevents caking and keeps the powder free-flowing.
Can you print hazard and handling marks?
Yes — product names, batch panels, handling symbols, safety text and barcodes, in one to eight flexographic colours.
Related: multi-wall paper bags · woven bags for heavy minerals · certifications
Tell us what your powder needs
Send the product, net weight, filling machine type and destination port. We will confirm the structure and quote within one working day.