Wet-Bag vs Dry-Bag Isostatic Pressing in Ceramics

Cold isostatic pressing compacts ceramic powder inside a flexible mould by applying pressure through a fluid. Wet-bag and dry-bag systems use the same pressure principle, but the tooling and production rhythm are different.

Quick choice

Wet-bag isostatic pressing

In wet-bag pressing, operators fill a flexible rubber or polyurethane mould with ceramic powder, seal it, immerse it in the pressure vessel fluid and pressurize the vessel. After compaction, they remove the mould and take out the green body.

This route gives strong shape flexibility and works well for prototypes, small batches and simple blanks. The trade-off is handling time. Each cycle needs filling, sealing, immersion, removal and cleaning.

Dry-bag isostatic pressing

In dry-bag pressing, the flexible mould is fixed inside the pressure vessel. Operators or automation feed powder into the mould, compact it, eject the part and repeat the cycle.

This route is faster and easier to automate. It suits repeat parts such as tubes, rods, insulators, nozzles and other shapes where the tooling can stay fixed. The trade-off is lower flexibility when product geometry changes often.

Comparison table

Quality checks

• Check green density uniformity along the part length and wall thickness.
• Watch for mould wear, powder segregation and trapped air.
• Control fill weight before pressing.
• Confirm green strength before handling or machining.
• Validate fired shrinkage after any tooling or pressure change.

Bottom line

Use wet-bag pressing when flexibility matters. Use dry-bag pressing when repeatability, speed and automation matter. Both routes need powder flow, fill weight and mould condition under control, otherwise the press can make a uniform-looking but weak green body.