TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The sight glass is formed by a flat disk. A wiper armature is mounted at the sight glass armature, comprising at least one rotatable- or pivotable wiper arm, which is operable from the outside of the fermentation container, and at least one wiper arm is present on the interior of the container facing the inside of the sight glass. The sight glass exhibits a round, a square, and/or an outer peripheral geometry symmetrical with respect to a sight glass midpoint. The wiper arm is rotatably or pivotally mounted on the sight glass, preferably in the region of the sight glass midpoint, and extends radially outwards. The wiper armature comprises a wave carrying the wiper arm, which is guided outwardly passing from the interior of the container through the sight glass armature, preferably through the sight glass of the sight glass armature, and is provided or coupled with an actuating element, preferably having a manually operable handle element, or an electrically, hydraulically or pneumatically operable drive element. The sight glass armature comprises at least one flushing nozzle guided from the outside of the fermentation container to the inside of the container interior, facing the inside of the sight glass, for cleaning the inside of the sight glass from the outside of the fermentation container with a washing liquid charged with predetermined pressure and/or a predetermined temperature. The sight glass armature comprises a mounting frame carrying at least one sight glass, which is inserted in an installation opening of the container side wall, and extends from the depth of installation opening with a tube and/or shaft-like formed frame portion carrying at least one sight glass in the direction of the container interior. The tube and/or shaft-like frame portion has a round or rectangular geometry and/or is made of at least one part, preferably several mutually connected gastight sheet metal parts. The tube- and/or shaft-like frame portion at its end pointing in the direction of the container interior free end portion, comprises a sight glass recording and recess carrying at least one sight glass in a window frame-, complete-, and/or gas-tight manner. The free end portion of the tube and/or shaft-like frame portion and the thus formed sight glass recording and recess is inclined to the inside and the bottom in the direction of the container bottom, such that the inserted planar sight glass is also inclined to the inside and the bottom towards the container bottom. The free end portion of the tube and/or shaft-like frame portion carries several mutually arranged sight glasses in different angular positions, preferably V-shaped angle of the tube and/or shaft-like frame portion and in each of its V-shaped limbs, a sight glass recording and recess is formed. The sight glass recording and recess comprises a supporting edge area on which the sight glass, preferably with an interposition of a peripheral seal, is applied with a sight glass edge region. A mounting element, preferably a mounting bracket is mounted on the sight glass edge region, preferably with the interposition of the peripheral seal, one of the sight glass edge region, or on the sight glass edge region and a sight glass front side. The preferred devices of several spaced, circumferential mounting devices, preferably screw connections are fixedly connected through the sight glass with the supporting edge area of the sight glass recording and recess. The installation frame has a mounting flange which in the assembled state at a the installation opening of the container side wall, carries a bounding edge region of the mounting hole in an installation connection, and is firmly connected by the container side wall, preferably by several fastening bolts. The mounting frame is made of plastic or steel, preferably stainless steel, and/or the sight glass is made of plastic or glass. The sight glass armature having a size and at least one sight glass is offset inwardly towards the container interior such that the sight glass armature receives moving head of a human observer in the immediate vicinity of the sight glass, and the sight glass gives a clear view on the container interior in the direction of the container bottom.