Qualitative Filter Papers-Grade 4: 20-25μm

Grade 50: 2.7 μm*
Retention of very fine crystalline precipitates.

The thinnest of all Whatman filter papers with a slow flow rate, these filters have a hardened and highly glazed surface, which also keeps the paper free from loose surface fibers.

Highly suitable for
qualitative or quantitative filtrations requiring vacuum assistance on Büchner
or 3-piece filter funnels.

Very strong when wet and will withstand wet handling and
precipitate removal by scraping.

In the electronics industry, the virtual absence of
fiber shedding is utilized in carriers for integrated circuits.

This grade is also available in Smear Tab format for wipe testing (e.g. testing of
surfaces for radionuclide contamination).

Whatman gridded filters have clearly defined grid lines spaced at 3.1 or 5 mm intervals.

The special ink used is nontoxic and completely
free from bacterial growth inhibitors.

Whatman black mixed cellulose esters are available plain for automatic colony
counting applications, as well as gridded to assist in manual counting procedures.

Black membranes provide contrast between residue or cell colors and the filter
without having to counter-stain the membrane.