As a coin collector, you will come across coins with all sorts of dirt and grime that needs to be cleaned off before you can fully assess the value and characteristics of the coin. Another issue with assessing coins is when they have burnt spots on them. With coins that have been burnt, it's difficult to tell what distinguishing characteristics might make the coin especially valuable. Use a cleaning process with household items before examining the potential treasure you've found.
Place a sheet of aluminium foil onto the bottom of a glass container. Smooth out any wrinkles.
Boil water on the hob or in the microwave and add it to the glass container.
Put the coin into the container so that it's sitting on top of the aluminium foil and completely submerged.
Measure out 3 tbsp of washing soda and put it into the container. Stir to dissolve the washing soda.
Allow the coin to soak in the solution until the water becomes room temperature.
Dump the water and examine the coin. The burnt residue should be removed or diminished. If you can still see residue, use new tin foil, water and washing soda to repeat the process.