STEP 1: WIPE
If you use the watch strap for some time, and because a watch strap rests against human skin, it can trap all sorts of things under it and attract just as many things onto it. So it’s important to properly wipe down your watch strap before washing it to prevent dirt from scratching the leather surface while you’re scrubbing it. Using a soft, dry cloth will do the job perfectly.
STEP 2: SCRUB
Take a soft cloth and a bucket of warm, soapy water to gently scrub both sides of the watch strap and pay particular attention to its edges. Then using patting it dry with a dry cloth.
STEP 3: CONDITION
Once your watch strap is clean and dry, treat it to a little conditioner treatment. The conditioner does to leather what moisturizer does to the skin—keeps it hydrated and soft. Keeping a watch strap hydrated makes it last longer while keeping it soft makes wearing it a more pleasurable experience.