Lately I've taken to the 'finger' test, as a last resort.
Having regularly used L'Art du Son and MoFi cleaning fluids on my Okki Nokki, and they do a fantastic job, but sometimes I still get the odd stubborn 'click'.
Now I gently run my fingertips across the whole surface, and sure enough I can feel tiny specks, and under a magnifying glass I can remove them with a fingernail or toothpick.
Having regularly used L'Art du Son and MoFi cleaning fluids on my Okki Nokki, and they do a fantastic job, but sometimes I still get the odd stubborn 'click'.
Now I gently run my fingertips across the whole surface, and sure enough I can feel tiny specks, and under a magnifying glass I can remove them with a fingernail or toothpick.