If you purchase an item normally classified as food but use it for another purpose, it is still treated as food and therefore, not taxable.
Example 1: A department purchases vinegar but uses it for cleaning. The vinegar is not taxable.
Example 2: A department purchases pumpkins in fall and has students decorate them for display in the office. The pumpkins are still considered food and are not taxable.
What are examples of items which do not apply to this rule? Items sold for medical or hygiene purposes, alcohol, tobacco, candy, bottled water, soft drinks, and prepared foods.
See: http://app.leg.wa.gov/wac/default.aspx?cite=458-20-244, #2b.