The people who create the art are only entitled to deduct the cost of the materials that went into the work. But artists (and writers and photographers) deduct the cost of all their supplies in the year they incur them. Thus the net effect of this is that the contribution that can be deducted by an artist for the gift of a work of art is zero.
In other words you can't get a double deduction. you expensed the costs of the material as a business expense. thus you are not entitled to a charitable deduction for the same costs. even an appraisal would not change the results.
