What is a characteristic of alginate as an impression material?

Alginate is characterized by its ability to expand slightly during the setting process. This unique property allows it to capture fine details of oral structures, making it ideal for taking impressions in dentistry. The slight expansion can help accommodate any discrepancies in the fitting of the impression tray or the anatomy being recorded, resulting in a more accurate representation when used for creating models.

The other characteristics do not apply to alginate. For instance, alginate does require water to set properly, which distinguishes it from materials that set without the need for moisture. It is also not classified as thermoplastic; rather, it is a cold-setting material that undergoes a chemical reaction upon mixing with water. Lastly, after setting, alginate is not rigid but remains somewhat flexible, allowing for easy removal from the mouth and manipulation without fracturing.