This simple device facilitates the use of any tube, helping to squeeze it evenly and gently. It consists of a base in a hole which is inserted the tube, and turning a key with slit for exciting a planar end of the tube. The base and key are made of wooden bars of appropriate dimensions. Their interaction is clear from the figure.
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TAPE INSTEAD OF THE FRAME
If there is no suitable photo frame it can be replaced by any opaque tape, stretched on the table of a photographic enlarger in the longitudinal and transverse directions. The ends of...
