A standardized small-scale mashing procedure used to assess malt quality.
For a congress mash, malt is measured into 50-gram samples and then milled. The milling may be coarse or fine. The milled malt is then extracted with four volumes of water at progressively higher temperatures to approximate decoction mashing.
The resulting wort is then "lautered" (filtered) and then tested in different ways. For example, malt modification is determined by the extract difference between the coarse and fine grains. Other tests that can be run include pH, color, viscosity, odor, free amino nitrogen, and final degree of attenuation.