This research proposed a new model of representational change in writing. In this model, two processes — the construction phase and the expression phase — are al ternatively repeated. In the construction phase, a mental representation of writing tasks changes from a propositional representation of sentence-by-sentence in text to a representation such as a summary of text, and finally changes into an abstract repre- sentation reflecting deeper understanding. The expression phase is the reverse of the construction phase; representation changes from abstract to propositional. Addition- ally, this research assumed that the expression phase consisted of an automatic process and a controlled process. The automatic process involves writing the main message, and the controlled process involves writing another sentence that adds information to the previously written sentence or gives concrete examples. After two experiments were conducted to confirm the hypothesis, the results revealed that a portion of the main written message was not related to the amount of resources necessary for the function- ing of the control system; moreover, the amount of resources required for the proper functioning of the control system facilitated a portion of the added sentences. These two results are significant in proposing a new model and understanding the writing process, and show that the mental process of writing includes an automatic process and a controlled process.