Filter Paper Grade 91 (10 µm)

Wet Strength Filter Paper Grade 91 is a high-strength qualitative cellulose filter paper engineered for vacuum filtration, pressure filtration and high-load wet processing.

With approximately 10 µm particle retention and reinforced wet strength, Grade 91 prevents tearing, fiber shedding and structural collapse during repeated washing, suction filtration and mechanical handling.

It is widely used when standard filter papers fail under wet or mechanical stress conditions.

What is Wet Strength Filter Paper Grade 91?

Grade 91 is a resin-reinforced qualitative cellulose filter paper manufactured from high-purity cotton linters. The wet-strengthening treatment significantly improves mechanical durability under wet conditions without affecting filtration performance.

It maintains structural integrity under vacuum pressure, liquid load and repeated washing cycles, making it suitable for demanding laboratory and industrial filtration workflows.

It is equivalent to Whatman Grade 91 and serves as a reliable alternative for routine analytical and process filtration.

Why Choose Grade 91 Instead of Standard Filter Paper?

• Standard filter paper tears during vacuum filtration → Use Grade 91
• Filtration requires repeated washing or handling → Use Grade 91
• High solid load or mechanical stress → Use Grade 91
• Routine low-stress filtration → Use Grade 2

Grade 91 is designed for strength-critical filtration, not general-purpose filtration.

Key Features & Advantages

• 10 µm particle retention– medium retention filtration
• High wet strength– stable under vacuum and pressure
• Resin-reinforced structure– prevents tearing and deformation
• Medium filtration speed– balanced workflow efficiency
• Low ash content (<0.13%)– reduces analytical contamination
• High mechanical durability– suitable for repeated handling

Technical Specifications

Performance Overview

Grade 91 is designed for filtration environments where standard qualitative filter papers fail due to tearing, clogging or structural breakdown under wet conditions.

Its reinforced structure ensures reliable performance under vacuum suction, pressure systems and wet handling conditions while maintaining consistent filtration behavior.

Typical Applications

• Vacuum filtration and pressure filtration systems
• Air and gas monitoring sample preparation
• Sugar and food analysis (e.g., sucrose testing)
• Pharmaceutical laboratory filtration
• Electroplating and chemical solution analysis
• Repeated washing or high-stress filtration processes

When to Use Grade 91

Important Notes

Not suitable for Kjeldahl nitrogen determination, because the strengthening resin contains nitrogen that may interfere with analytical results.

Grade Comparison

Ordering Information

Custom sizes, OEM/private label and bulk supply are available. Contact us for technical support and distributor pricing.
Download PDF Datasheet

FAQ

What is Grade 91 used for?

It is used for high-strength filtration such as vacuum filtration and repeated washing processes.

What makes it different from standard filter paper?

It contains a resin reinforcement that significantly increases wet strength and durability.

Can it be used for vacuum filtration?

Yes, it is specifically designed for vacuum and pressure filtration.

What is the particle retention?

Approximately 10 µm.

Why is it not suitable for Kjeldahl analysis?

Because the resin contains nitrogen which interferes with nitrogen determination.