A test to determine the amount of clay-like materials in a water-base drilling fluid based on the amount of methylene blue dye absorbed by the sample. Results are reported as "MBT" and also as "lbm/bbl, bentonite equivalent" when performed to API specifications.

Why is methylene blue used in this test?

The methylene blue (MB) dye test is a new test that qualitatively indicates the presence of hydroxyl radicals through an immediate, distinct bleaching of the MB dye on a paper test strip after applying an aqueous sample containing hydroxyl radicals.

What is the principle of methylene blue test?

Principle. The test relies on the fact that methylene blue solution is blue in the presence of oxygen, but will lose color as oxygen is depleted. Bacteria in milk ferment lactose (milk sugar) to form lactic acid. During this process oxygen is used up and electrons are released, which react with methylene blue.