There are lots of different types of glass, and depending on the style and treatment, cleaning methods can vary. You may have to use a bottle brush to get down through the narrow neck of a bottle to give the bottom a good scrub or opt for a light wipe to avoid taking the gilding off a decorated decanter or platter. Knowing whether there's a film or coating over a piece of glass will give you clues about whether it's safe to use some elbow grease or an abrasive to remove rust spots or mineral deposits. You'll be able to use more pressure to get down into the pitted or upbraided areas of frosted glass than you would be on a piece that has a gold leaf finish. The more you know about the glass involved, the easier it will be to understand how aggressively you can work at getting it clean. Before you stir up the suds, take the time to do your homework on the proper cleaning method for your antique glass.