Cleaning Cloudy Glass and “Sick Glass”

Q: A few of my favorite vases are cloudy below the waterline, and some have white horizontal lines. I also have a collection of antique bottles—most have patches that look like they’re coated with a white film. I’ve tried soaking them in soapy water and using bottle brushes to clean them inside. Nothing works! Can I do something to fix my cloudy glassware?

A: It depends. If the discoloration was caused by a layer of minerals left behind as water evaporated, you may be able to remove most or all of the discoloration. Cheap white vinegar and water can often dissolve hard water marks like these. To try to dissolve the marks, you can try the following.

How to Dissolve Mild Cloudiness

Although vinegar (acetic acid) can be corrosive at high concentrations, it’s considered safe for glass. However, it may not be safe for decorations applied to glass, such as gilding or paint. It can discolor those decorations, or make them peel off.

Glass that’s been coated with a translucent colored film should not be soaked in vinegar. However, blown or molded art glass that was colored while in its molten state is safe to soak. The color in this glass comes from minerals embedded in the glass itself.

Using vinegar to dissolve mineral deposits

To see whether your glass can be restored, try the following steps:

• Fill the vase or bottle up with vinegar and let it sit overnight.
• In the morning, pour out the vinegar, then clean the inside of the glass vessel thoroughly with a bottle brush and rinse well with warm (not hot!) water.
• If you don’t have a bottle brush, empty out the vinegar, then add a tablespoon of uncooked rice to the empty vessel. Fill it halfway with water, and shake it vigorously for one minute. Drain the water and compost the rice or throw it in the trash. (Don’t empty it down the sink; the rice will swell as it absorbs water, and could clog your drain.) Rinse the vessel well with warm water.
• Dry it well with a towel, then turn it upside down to dry and drain. This will often significantly improve cloudiness, or even make it disappear entirely.

Water temporarily hides cloudiness

Filling damaged glass with water can temporarily fill fissures and minimize them, or even make them temporarily invisible. If you love a vase or bottle with mild cloudiness, it might look just fine with water inside. I often group several of my pale blue and lavender antique bottles together to display individual floral stems. They look lovely when filled with water and topped with a delicate long-stemmed freesia or fern frond.

To avoid creating new lines on the glass, replace the water frequently, or cork the top of the vessel to avoid evaporation.

Vaseline on glass?

While “Vaseline glass” is a thing (it’s transparent yellow or yellow-green glass that gets its color from trace amounts of uranium), that’s not what I mean. Try applying a tiny amount of Vaseline or generic petroleum jelly to an area of glass discolored by minerals or micro-fissures. The jelly gets into the tiny cracks, and this often makes the cloudiness less obvious. You need to use a very small amount of jelly, so try applying it with a Q-tip. For a taller vase or bottle, use a long cotton swab with a wooden stick, such as you’d find in a hospital. (You can buy these swabs online for not much money.) Once applied, use a fresh, dry swab to gently rub it in and remove any excess.

What Causes Cloudy Glass or Sick Glass?

Unfortunately, calcium and other minerals sometimes become part of the glass itself. They enter the glass through microfractures, and vinegar or can’t always flush this away. Washing cloudy glass or crystal with hot or cold water can cause it to expand or contract. This causes tiny fissures, and these cracks, or the minerals that get into them, can cause the glass to look permanently cloudy.

High temperatures & dishwasher detergent

Old glass or fine crystal can be especially sensitive to extreme temperature changes or harsh chemicals, which is why you should never wash such items in a dishwasher. They should be washed only with mild soap and warm water. Hand dry as much as possible before you air-dry them the rest of the way. Don’t put them away damp; minerals left in the water droplets can actually cause cloudy glass. They leave spots that can become permanent.

Inherent flaws, or long-term exposure to minerals in soil

Glass can have built-in faults caused by the chemical composition in the original glass formula. These faults make glass grow cloudy over time. It can also develop a haze by prolonged contact with mineral-rich soil.

Embrace the quirks that make it special

When bottles are buried in landfills for long periods, minerals enter the glass from the surrounding soil. As water seeps into the ground through the earth, it carries dissolved minerals from the soil. This mineralized water fills or surrounds the bottle, and temperature changes make the glass expand and contract. The minerals enter microfissures in the glass or bond to its surface, and become permanent parts of the bottle. These can cause an iridescent sheen to develop over part or all of the bottle.

You can see this elegant iridescence on Victorian medicine or liquor bottles that were left in landfills for decades before being dug up. Roman glass bottles found after centuries underground are often wonderfully colorful and shimmery after long exposure to minerals. The resulting multicolored sheen is highly prized by glass collectors. I think of this so-called damage as an example of wabi-sabi—the damage to the glass is actually the element that makes it special. In this case, you could consider cloudy glass a feature, not a bug.

Lack of prompt cleaning

Leaving wine, lemonade, or other acidic liquids inside glass can also etch it. It’s important to rinse glasses before bedtime if you don’t wash them shortly after dinner. Leaving acidic liquids in lead crystal decanters or wine glasses can leach small amounts of lead into the liquor, too. The amounts are minimal and not considered dangerous. However, to avoid exposure, it’s best not to leave alcohol sitting in decanters for long periods of time.

Glass Needn’t Be Perfect to Be Beautiful

Don’t blame yourself if your bottles, vases, or other glass items become hazy over time. Glass composition differs radically from one piece to another, and even excellent care can’t guarantee that glass will maintain its luster forever. Its fragile and temperamental nature is part of glassware’s beauty.

Want to learn more about glass? The Corning Museum of Glass in New York provides a wealth of information, history, and imagery on their website.

At top:

Antique bottles dug up from landfills with cloudy or iridescent patches | Laura Grey