Eased counting process

In microbiological colony counting procedures, the color contrast between the surface and the colonies facilitates the counting process.

Plain or gridded

Many microbiological techniques include colony counting after incubation as the standard method of quantitation. Whatman gridded filters have clearly defined grid lines spaced at 3.1 mm 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.

Sterile filters

For those laboratories preferring to use membranes sterilized by autoclaving for microbiological work, Whatman provides black gridded membranes in packs with pads ready for laboratory autoclaving.