Abstract: A plurality of petri dishes or other glass or plastic containers are coated on the inside bottom surface of the containers by passing the containers through a coating or layering apparatus. The apparatus includes an indexing conveyor to sequentially pass the open containers through a filling station where an amount of a coating material is applied while tilting the container to one side thereby distributing the material to the entire bottom surface of the container. The containers are conveyed to an aspirating station to aspirate excess material while tilting the container toward the aspirating nozzle. Subsequent to the aspiration step, the containers are tilted in the opposite direction to distribute the material in the container. The material is then dried and the containers stacked and packaged. The coating material includes metal ions such as calcium or other divalent metal ions, in a suitable carrier that is able to bond the bottom inside surface of the container.