Buying a wedding gown is often a bride-to-be's biggest decision. After the nuptials, it's important to clean and care for such a garment properly -- otherwise, the dress could get ruined.

The Matich family thought they’d taken the right steps to take care of a wedding dress. Twelve years ago, Jeanne Matich Maroney walked down the aisle in a beautiful white gown. The same day, she made her little sister, Julie, a promise.

"I had said to Julie, you know, if you're interested in wearing my gown, I would be honored if you did," said Jeanne.

Julie cherished the idea. All grown up and engaged, she thought she'd take her sister up on her offer.

"I thought it would be really cool to wear her dress," said Julie.

The gown, however, hadn’t aged well. It was discolored and covered with stains.

"It just wasn’t the same dress," said Julie.

To preserve the gown, the Matiches had paid a company $150 to give it a special cleaning and store it in a hermetically sealed box.

"It was indicated that you were not supposed to open it and that it needed to be taken back to the original company," Jeanne said.

"It wasn't until now, 12 years later, that we've discovered, in fact, it was not cleaned or preserved," she said.

When the stained, wrinkled gown was shown to an expert at the National Cleaners Association (NCA) headquarters in Manhattan, he wasn’t surprised.

"This has happened more than we'd like to think," said analyst Alan Spielvogel.

Experts at the NCA, who do museum-quality restorations, said it was clear the dress had not been preserved correctly.

"It might have been that the stains weren't completely removed and then oxidized from age," said Spielvogel.

To properly store a wedding gown, you should:

-- Open up the box and air out the dress every few months. -- Use an acid-free muslin bag if you plan to hang it. -- Never use vinyl or plastic bags. -- Consider cold storage for long-term keeping.

For more tips from the NCA on wedding gown care, click here.

To clean the gown, taking it to a dry cleaner soon after it's worn is a good idea, but make sure he or she has expertise dealing with fine fabrics.

As for Jeanne's dress, Spielvogel has offered to try to restore it as best as possible. Watch Ask Asa to learn how that turns out.