I am a collector and seller of vintage costume jewelry. For the past few years I have purchased many collector books on the subject. I have asked many questions of local dealers, and dealers online, who I've met while purchasing jewelry, or through social networks.
There are quite a few differences of opinion in the cleaning of vintage costume jewelry, and storage also.
I have been told by some to use a damp soapy cloth to clean dust and dirt from the jewelry piece, then wipe again with a water dampened cloth, and then dry. Others have told me to use a Q-tip dampened with water, while some have said to use Windex!
One of the comments was that the alcohol in the Windex would dry off, while water sitting on the jewelry would cause harm. I really wondered about the Windex...
So, I asked an expert! I talked to the very friendly lady at our local gold and gem shop. She recommended using a Q-tip dampened with water, only if there was noticeable dust and dirt that had to be removed. Any Windex, or jewelry cleaners, would damage vintage costume jewelry! Soaking the piece with water would cause any rhinestones to loosen. A soft cotton T shirt fabric is the best thing to use to wipe any vintage costume jewelry piece.
I also asked her about an old 1940's necklace that had green residue on it. She told me that was oxidation of the metal, so the piece could not be cleaned.
I've also learned that wrapping rhinestone jewelry in bubble wrap, is not a good practice, as the plastic will 'deaden' the stones...they will turn dark! As I have received rhinestone jewelry from a few sellers who wrapped the jewelry directly in plastic, I am checking all of my stock. Wrapping the pieces in white tissue paper, or soft cotton fabric, first, is much better for your jewelry!
I certainly would not want to ruin any of my vintage costume jewelry, especially this beautiful Lisner bracelet and earrings set, which is one of my favorites!