Final answer:
Impression material on a spatula can be removed by cooling, submerging in water, or rubbing with a cloth, and heating may also be used with caution.
Step-by-step explanation:
To remove impression material that has set on a spatula, one effective method is by cooling the material, submerging the spatula in water, or rubbing it with a cloth. Heating the spatula can also be a viable method to soften certain types of impression materials, which makes it easier to peel or scrape off the hardened substance. However, care must be taken when using heat to avoid distorting the spatula or causing burns. Additionally, some impression materials may have specific removal recommendations, so always check the manufacturer's instructions.