A process for forming a three-dimensional article in sequential layers in accordance with a digital model of the article. The process comprises the steps of defining a layer of a first liquid, applying a second liquid to the first liquid layer in a pattern corresponding to the digital model, and repeating these steps to form succesive layers. The first liquid comprises a first active component and the second liquid includes a second active component capable of reacting with the first reactive component so that the article is built up in layers.