In order to get the very best sound and response quality you should remove any remaining rosin from the string.
During breaks in playing, we recommend that you wipe off any remaining rosin from the string with a soft cloth.
After playing on a weekly basis at least, make sure to clean the string with Pirastro string-cleaner.
You can also apply a little bit of string oil to the strings at the fingerboard area. Use the string oil sparingly – a small drop on the cloth is enough.