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Bottom-mount sinks

Bottom-mount or under-mount sinks are installed below the countertop surface. The edge of the countertop material is exposed at the hole created for the sink (and so must be a carefully finished edge rather than a rough cut). The sink is then clamped to the bottom of the material from below. Especially for bottom-mount sinks, silicone -based sealants are usually used to assure a waterproof joint between the sink and the countertop material. Advantages of an undermount sink include superior ergonomics and a contemporary look; disadvantages include extra cost in both the sink and the counter top. Also, no matter how carefully the cut out is made, the result is either a small ledge or overhang at the interface with the sink. This can create an environment for catching dirt and allowing germs to grow.

Solid-surface plastic materials allow sinks to be made of the same plastic material as the countertop. These sinks can then easily be glued to the underside of the countertop material and the joint sanded flat, creating the usual invisible joint and completely eliminating any dirt-catching seam between the sink and the countertop. In a similar fashion, for stainless steel, a sink may be welded into the countertop; the joint is then ground to create a finished, concealed appearance.