Qualitative Filter Papers-Grade 5: 2.5μm

Cellulose extraction thimbles are produced from high-quality alpha cellulose cotton
linter and have excellent mechanical strength and retention.
Standard single thickness thimbles have a wall thickness of approximately 1 mm
(10.0 μm nominal particle retention).

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.