I downloaded this from somewhere on the internet years ago; I apologize that I cannot cite the source. As I recall, he was a wine-loving chemist. You may find it helpful:
removing residue; no stink, no scratches, no spots
Here are some suggestions, but there are pros and cons to each: the most effective and fastest routes entail more risk to the glassware.
To help understand how to remove the stains, keep in mind what the stains contain:
a) tannins [the older the wine, the less water-soluble the tannins can become];
b) pigments originally within the wine skins [and now oxidized and more colored; these dissolve well in alcohol],
c) residual and unfermentable sugars [various types; these dissolve easily in water],
d) acids [tartaric, malic, lactic, citric, etc., all of which are moderately water soluble, and very soluble in alkaline solution, but are physically trapped within the viscous residue]
e) plus an array of other organic molecules.
So the goal is to find something that dissolves these molecules -- or which chemically modifies (derivatizes) them into something else that will dissolve more readily.
1. Use straight bleach.
Pros: it reacts with colored organic materials so as to not only modify their structure such that they don't absorb visible light (‘bleached'), but, more importantly, produces higher water-solubility in the resultant organic material. Bleach reacts only with what it can physically reach; if the hardened residue presents a hard outer wall to the bleach or other solvent, it will take time for the wall to soften before the bleach-induced chemical reactions occur and water-solubilization of the oxidized materials happens.
Cons: it stinks, it damages your skin, accidental splashes put holes in your clothes, and its alkalinity will, given enough time, visibly etch the crystal. It transforms the originally smooth surface of crystal (and regular glass, Pyrex, etc.) into a rougher surface which looks frosted. This change is permanent, and visually the glass looks ruined.
Tip: use only enough bleach to cover the residue. Replace the bleach several times, each with a fresh pour. And avoid exposing the glass to bleach for more than, say, about fifteen minutes total, especially if it's not the first time you've hit that glass with bleach. Bleaching is a labor-intensive, effective route requiring a bit of caution.
2. Baking soda and water (as suggested elsewhere in this thread):
Pros: Baking soda (sodium bicarbonate) is cheap. I haven't tried this route but I would imagine that part of the effectiveness of a paste of baking soda comes from its mild abrasiveness -- like that of an ultrafine sandpaper. If its mildly abrasive action works, then well and good. You may first want to soak the residue in water overnight to try softening it before using the bicarbonate.
Cons: not only can the abrasiveness of this solid (or as a paste) permanently scratch the surface of the glass, but it might also, but at a greatly reduced rate, chemically etch the surface in a manner similar to bleach.
3. ‘Near-neutral organic solvents'
In thinking about this, why not try to dissolve the residue in the glass by using the same solvent in which the residue was originally dissolved, i.e., wine? Use a cheap dry white that already has, on its own, relatively few of the types of molecules (acid, color, tannin, and sugar) which you're trying to dissolve within the residue. That flabby over-oaked cheap Chardonnay now has a purpose for existence. 8^) Alternatively, pour in a bit of rubbing alcohol, which is 70% isopropyl alcohol and 30% water. The isopropyl alcohol can slowly dissolve some of the colored organics in the residue, and the water will dissolve the acids and sugars.
Pros: convenient; very little effort.
Cons: it's slow. The drier/harder the residue, the slower the rate of solution. This route could easily require many, many hours.
Tip: cap the wine glass with a tight cover of Saran wrap. This will help reduce the rate of loss of water and alcohol from the ‘solvent'. If you use wine, periodically swirl it and ‘freshen' it after a half-day with a new small pour, then re-cover the glass with Saran.
4. Soap and water.
Pros: cheap and convenient.
Cons: slow, sometimes unacceptably slow. And a soap solution, being mildly alkaline, can slowly etch crystal, especially if the glass repeatedly sees overnight exposure to soap. See ‘bleach' above. The first evidence of etching is a purplish color on the surface of the glass, especially when compared to the color of a cheap, thick waterglass. The purple color comes, in part, from preferential scattering of short wavelengths (purple/blue) by, in this case, small pits on the glass's surface. For analogous reasons the sky is blue because of preferential scattering of short wavelengths by dust and other small particles in the air, just as the blue haze of a smoke-filled room is caused by light-scattering by smoke particles. (Smog is a different case, as some of its constituents are colored.)
Riedel and other crystal inevitably receives microscratches when it's dried with any towel; what's worse is that detergent's optical brighteners and cheap perfumes – which remain on a clean, washed dish towel – are transferred to the glass, especially when drying the inside of the glass with a towel. I recommend a no-scratch/no-residual stink method of drying a clean wine glass: after washing with top-quality dish soap, rinse well with tap water, and then rinse the inside twice with small pours of distilled water. Over the sink, pour the water from the first glass over the outside of the next glass. Do the same for the next glass, etc., and let them all air-dry. No spots, no stink, no scratches.