A technique for transferring an identical pattern of bacterial colonies from one petrie plate (the master plate) to a series of other plates containing different media. A plate containing bacterial colonies is pressed against a cylindrical block covered with velveteen, resulting in the transfer of many of the bacteria from each colony onto the corresponding position on the velveteen. Then a series of sterile plates are sequentially pressed against the velveteen to transfer cells from the velveteen to the corresponding position on each petrie plate. After incubation, if the cells can grow on the particular medium in a plate colonies will appear at identical positions on each plate. Typically about 10 replica plates can be made from each master plate with about 200 isolated colonies on the master plate. Thus, it is possible to quickly screen a large number of colonies for a variety of phenotypic characteristics.

A technique for transfer of colonies from one Petri dish to another, such that their relative positions on the surface of the agar medium are retained.

In molecular biology and microbiology, replica plating is a technique in which one or more secondary Petri plates containing different solid (agar-based) selective growth media (lacking nutrients or containing chemical growth inhibitors such as antibiotics) are inoculated with the same colonies of microorganisms from a primary plate (or master dish), reproducing the original spatial pattern of colonies. The technique involves pressing a velvet-covered disk to a primary plate, and then imprinting secondary plates with cells in colonies removed by the velvet from the original plate. Generally, large numbers of colonies (roughly 30-300) are replica plated due to the difficulty in streaking each out individually onto a separate plate.