Holding Solution. A solution in which patina work can be halted and the item stored until some further operation is performed; cream of tartar (potassium bitartrate) effectively stops all chemical action until it is thoroughly rinsed. A very light nitric acid solution will perform the same stopping action; but care must be exercised in preparing the solution, as too strong a solution may be corrosive to the metal surface. Often the last batch processed late Friday afternoon is placed in a cream of tartar bath; Monday morning the holding solution is rinsed off, and work continued for a correct patina finish.