Tray(redirected from impression, maxillary tray)
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a flat vessel for processing photographic paper, film, and plates and for etching engraving plates. It has a ribbed or contoured bottom and a spout in one corner for decanting the solution. Trays may be made of glass, plastic, enameled iron, porcelain, or stainless steel in sizes that depend on the dimensions of the photographic materials being processed.