Edible chometz mixtures must also be removed before Pesach. Mixtures that are either inedible or edible only for ill people, although permissible to own over Pesach, may not be eaten until after Pesach. (ShA1,4 — MB20)
Inedible chometz mixtures, although forbidden to eat, you may benefit from them as long as the chometz was mixed in before Pesach. (MB22)
Chometz that has become moldy before Pesach to the extent that even a dog will no longer eat it does not need to be removed. If a dog will still eat it, even though a person would not, it still needs to be removed since it can be used as sourdough. (ShA2 — MB9,10)
Items on which chometz-based laundry detergents and starches have been used may be owned on Pesach. (ShA3)
Nevertheless, do not use those items near food if particles of the chometz could possibly fall into the Pesach food — e.g. tablecloth, napkins, clothing. (MB16)
Do not ridicule the custom to scrape walls and chairs that have been in contact with chometz. (ShA6 — MB28)
Many poskim hold that edible chometz must be removed even if less than a kezayis. But if the chometz is both less than a kezayis and a bit filthy, no one holds that you must remove it. (MB33)
Chometz that has been set aside for sitting upon and has been plastered over all its surfaces is permitted to own on Pesach but not to eat. (ShA9 — MB41,42,43)
You are allowed to dip your quill into chometz-based ink and write with it on Pesach. Even if you put the quill into your mouth and swallow some ink — it is not a problem since the ink is not fit for a dog to eat and you do not have intention to consider it food. (ShA10 — MB45)
Vessels used for chometz during the year that can be cleaned thoroughly should be cleaned and stored away for Pesach. (MB47)
Bread baskets that cannot be thoroughly cleaned and there is a suspicion of remaining crumbs — should be cleaned well and put away into a room that is not regularly used. (MB51 — ShaH82)
