How to Seal an Envelope

Use conventional envelope moisteners. These are typically plastic bottles topped with a small sponge and are available at most office supply stores. To use this type of envelope moistener:

• Hold the bottle vertically, sponge-end down, and run it along the strip of envelope glue while gently squeezing.
• Be careful not to squeeze the bottle too much, or you may over-moisten the envelope and leave it sodden or puckered.
• This method is more efficient when you need to seal a large number of envelopes at once (making it useful for sending out wedding invitations, holiday cards, etc.), but it can become messy if you squeeze the bottle too enthusiastically.

Use a combination moistener/sealer machine. These represent the latest in envelope-sealing technology and will both moisten and seal your envelopes for you. Electric moistener/sealer machines will automatically feed envelopes through, while manual machines must be hand-fed, potentially making them as labor intensive as other, lower-tech methods.

• Because these are a relatively new technology, they’re not without their glitches, and some models may work better than others. Be sure to do your research before investing.

Try a vintage envelope moistening wheel. If you prefer an old-school approach, you can find envelope moistening wheels online and in stores specializing in vintage office equipment. Most are ceramic and feature a cylindrical wheel perched in a rectangular basin, which makes them rather resemble an office tape dispenser. To use one, fill the basin with water, run the envelope’s glue strip across the top of the moistened wheel (like running a knife blade over a whetting stone), and fold and press the envelope flap to seal. Though a bit old-fashioned, these envelope moisteners have the advantage of durability—the ceramic wheel won’t disintegrate as sponges do.

Use a sponge, q-tip, inexpensive 1/4"-wide paint brush or cotton swab to help you moisten your envelopes. This approach will spare your tongue and may allow you to seal a larger number of envelopes than the tongue alone could handle. To use this method, get a small bowl and fill it with warm water. Lightly moisten your sponge, q-tip, paint brush or cotton swab in the water and swipe it across the glue of the seal. Fold the moistened flap and press down on it to seal the envelope. But be judicious with the amount of water you moisten with. Start light and re-apply if necessary—if you over-moisten, the paper may become soggy or begin to pucker.^[2]

Use tape or glue. You can simply tape the envelope shut by folding the flap of the envelope down and running a strip of regular tape across the top. For a less DIY-look, you can use double-sided tape or glue along the inside of the flap before folding down and sealing. Many prefer to use a glue stick over traditional liquid glue because it’s less messy and dries more quickly, but both are viable options.

Use stickers. If you want to add a little unconventional personality to your envelope, you can seal it with stickers—just fold the flap down and place stickers across the line where the flap and body of the envelope meet. But be aware that stickers may not leave the most professional of impressions and may be less secure than other methods.

Seal it with nail polish. Nail polish, it turns out, is one of the great household multi-taskers, and one of its lesser-known qualities is its ability to save you trouble sealing envelopes—and to offer a particularly strong and secure hold while doing it.^[3] Just swipe the nail polish along the inside of the envelope flap and press it shut. You might want to opt for clear nail polish to avoid giving the envelope’s seal an odd color—unless, of course, that’s the look you’re going for.