Why is millwork stored in the shop rather than onsite before finishing and coating?

Storing millwork in the shop rather than onsite before finishing and coating is primarily about maintaining control over the product's environment and minimizing potential issues. When millwork is exposed to the variable conditions found at job sites, such as fluctuating temperatures, humidity, and exposure to dust or debris, it can lead to significant problems. For instance, moisture can cause warping, swelling, or cracking in wood products. Keeping millwork in a controlled shop environment allows for proper acclimatization, ensuring dimensional stability and allowing the finish to cure correctly.

In this context, while concerns about dimensional stability and potential bleaching or oxidation/discoloration are valid considerations, they fall under broader issues that might arise during improper storage or exposure to adverse conditions. Thus, the correct answer emphasizes the array of possible problems that could compromise the integrity and quality of millwork if stored onsite without the proper conditions for protection.