ACC “Altus” Series In-form retarders are designed for use in horizontal or vertical formwork. They are solvent-based and look like paint, coming in different colors to designate the depth of etch or aggregate exposure. When applied to formwork they provide an abrasion-resistant surface so that concrete, while being placed, doesn’t remove retarder from the forms. The retarder coating the form reacts chemically with the concrete preventing the immediate depth of the concrete from setting. After the concrete has set and the form pulled, the surface of the concrete that was in contact with the form may be flushed with high pressure water. This rinses away the cement revealing the desired depth, exposing aggregate or simply imparting a sandblast or acid etch effect.