Use CROWN urn cleaner when your urn (or in fact, any hot water appliance) becomes darkened and has an appearance of being dirty and rusty.  This discolouration is caused by sediment deposits from the water you are using.
 
Such desposits (if thick enough on your heating element) can give the impression that the urn is faulty and requires repair; whereas, chances are, it just needs a good clean-out.
 
The cleaning process is ridiculously simple:
1. Fill the urn with water (approx half full)
2. Add a tablespoon of CROWN Urn Cleaner
3. Boil for between 10 and 15 minutes
4. Carefully empty the contents of the urn
5. Rinse the urn twice with cold water
6. You are now ready to fill your urn with water and continue to use, as per normal.
 
Detailed instructions are on the bottle.
 
The CROWN Urn Cleaner is made from natural ingredients.