Well if you are meaning from new then I wash in the washer at 90c a couple of times (with detergent) then use as sill cloths for a 2-3 weeks to break in ( just wash along with other scrim now) No need for detergent as if used trad then they absorb enough detergent from the cills to come clean in the machine at 60-70c. That's buying the pre-washed scrim, non pre-washed take an age to break in. There is some new more absorbent blue microfibre out that's supposed to be a lot more absorbent than normal microfibre, it was reviewed very positively in the Window cleaning mag. Better than scrim apparently.