Dull silver plating

Q: My silver plating bath is producing a dull, burned finish, what should I be looking into to get a bright deposit? 

A: Look into the concentrations of the following components: [Ag], [CN], [CO3], and [Brightener]. Different corrective actions should be taken for each component. If any component is too low the obvious recommendation is to add sufficient amounts of that component based on tank size to restore optimal operating conditions. The harder issue is having excessive concentrations of these components. If all components are proportionately high, dilute the bath. However, to fix individual components consider
the following:

• Adjust silver: Continue to operate the solution but replace the anodes with inert anodes (platinized titanium) to gradually decrease the silver concentration, then restore the silver anodes. 
• Adjust cyanide: This is trickier; If the concentration of silver is low, add silver cyanide to complex the free cyanide while raising the silver concentration. However, if the silver concentration is not too low then dilute the bath and make the required additions. At all times avoid any method that involves acidifying the cyanide bath (i.e. gassing off). 
• Adjust carbonate: Is the bath sodium or potassium cyanide? For sodium cyanide, you can simply freeze the bath using a chiller and remove the solidified carbonate. For a potassium cyanide bath use calcium nitrate or calcium hydroxide to precipitate the carbonate. Utilize a stoichiometric calculation to ensure you do not add excessive calcium as this will produce a jelly-like substance which will harm the plating performance 
• Adjust the brightener: Excessive brightener will in fact produce dull deposits. There are two types of brighteners used in silver plating baths, organic and metallic. Metallic must be diluted as it cannot be removed by other means but organic brighteners can be carbon treated to lower concentration.