If you could post a picture of the Decanter we may be able to help Id it for you. On just general Cleaning of glass Denture cleaner works pretty well, However if what you have is called Dirty Glass, this is a much bigger problem. Fine Crystal that has been cleaned in a Dishwasher, can develop what is called Dirty Glass. This can be next to impossible to clean. I had a nice set of Fostoria Stemware that was Dirty Glass, a foggy look on the glass, and when you attempt to clean it, it comes back once it is dried. I had read a few method of cleaning it but none really worked at all. Look up Cleaning "Dirty Glass". Fine Crystal Glass should never be cleaned in a Dishwasher and when it is, it can develope a mineral Deposit on the glass. If you do find a way to clean Dirty Glass Please let me know, many times I find this dirty Glass on nice pieces but won't touch them because I have not found a way to clean them.