Early on, union leaders supplied hundreds of rolls of blue painters tape to protesters whose Capitol camp-out began Feb. 15 and ended Thursday. Police told them the blue tape was gentlest on the stone walls and railings. The Capitol's interior features 43 varieties of stone.

The union also began raising money early in the protests for food, supplies and other expenses. It plans to use some of the $67,000 sitting in that fund now to help the state cover cleanup costs.

Meghan Thumm Mackey, an art conservator who has a studio in Middleton, said that even painters tape that's left on too long can leave adhesive residue on stone surfaces and require professional evaluation and removal using a solvent such as acetone, the main ingredient in nail polish remover, with a cotton swab.

That can get expensive, she said, as the small field of people like her trained in art conservation typically charge $100 an hour or more. In Stephan's memo, the state would need to rely heavily on such experts, which to clean 240,000 square feet inside would cost $6 million. He estimated another $1 million to clean and replenish the grounds outside and up to $500,000 for the initial assessment.