Do not leave your leather untreated, otherwise it gets dry and becomes brittle. Here is how to keep it soft and clean:

# clean your collar or lead with a soft cloth removing first dirt

# lead / collar should be dry

# apply saddle soap (not standard soap)

# wipe down and rub mixture onto surface

# allow the leather to absorb

# buff the leather aftwards with a clean dry cloth

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Brass products can oxidize, and due to this, they can darken. This is not a manufacturing defect but a natural property of brass.

# cover the leather parts of your collar or lead with a tape or cloth

# for brass cleaning use gentle commercial brass cleaner or vinegar essence

# use a clean soft cloth and apply the brass cleaner / vinegar

# rub / polish carefully (without touching the leather) the brass parts

(Little homemade recipe for brass polish, which also works on corroded brass: mix 1/2 cup of vinegar, teaspoon of salt, sprinkling of flour until it forms a paste. Spread the paste on the brass. Allow to sit for a few minutes. Rinse gently with water and dry.)