Proper Storage for Condenser Microphones

Large-diaphragm condenser microphones are sensitive to dust and humidity. Learn how to keep your new microphone safe with these simple tips.

Moisture is the enemy!

Condenser microphone capsules can be ruined by moisture. Therefore all condenser microphones should be kept dry between sessions.

After a vocal session, allow the microphone to dry out for a few hours. Moisture from breath can condense on the microphone grille and capsule, especially if you place the vocal mic too close to the singer's mouth.

We recommend storing condenser microphones in a plastic bag with desiccant. We ship every Roswell microphone in a poly sleeve, with a desiccant pouch, for this reason.

Refresh desiccant annually

Desiccant pouches do not last forever. As little as 30 minutes' exposure to humid air could consume 50% of the desiccant's drying capacity. If you want to keep your condenser mics dry between sessions, the desiccant stored with the mic must be fresh.

See the graph at right. Silica gel can carry ~33% of its weight in water -- but in a humid environment will hit half of that capacity within 75 minutes of exposure.

"Molecular sieve" desiccant is more aggressive at pulling moisture from the environment; in a sealed container it will actually pull moisture out of silica gel (!). A packet of molecular sieve material will lose half of its drying capacity within roughly 30 minutes of exposure to humid air.

Therefore desiccant pouches must always be stored in an airtight container (such as a sealed plastic bag), so that they retain the ability to "adsorb" moisture when you put your microphone into that bag.

You can purchase bulk desiccant pouches inexpensively on Amazon. We recommend replacing the desiccant pouches for your condenser mics annually, or more frequently if you live in an area with high ambient humidity.

We do not recommend trying to "recharge" desiccant in the oven. You won't know if it works, and you might set fire to the pouches along the way. Buy fresh desiccant periodically instead.

Beware of foam for long-term storage!

Polymer foams such as polyurethane and polyethylene can degrade over time. This is unlikely to affect any new Roswell mic in the next 20 years, because we've used a type of foam that should last a very long time.

Still, we always recommend storing microphones in plastic bags within the case, rather than laying the microphone directly into the foam, just in case. The image at right shows an old U87 microphone that had been left in a foam-lined case for too long. The foam disintegrated and reformed on and within the microphone, damaging the mic's capsule.

How to build a "dry box" for microphones

If you live in an area with high humidity, your microphones will last longer if you store them in a dry box. You can create this relatively easily:

1. Buy an "weatherproof storage container" or "gasket box" on Amazon. The item shown at right holds 32 qt; it measures 18x14x10 inches, which could hold six or more microphones depending on how they're stacked.

   Amazon links:

   • 32 qt (18x14x10 inches)
   • 37 qt, flat (23x18x8 inches)
   • 16 qt 3-pack, stackable (15x10x6 inches)
   
   
2. Put 20-30g of silica gel or molecular sieve desiccant pouches inside. Replace them annually.
   
3. Optionally, put a box of indicating silica gel inside, so that you know when the interior environment has become damp. Indicating gel turns color when it is no longer dry.

Store the microphones inside that box. Take care that you never leave the box open for any amount of time. Replace the desiccant every 6-12 months -- sooner if the box is large or is opened frequently, or if mics are used for vocals and put away before they've had a chance to dry.

It is not necessary to store dynamic mics or passive ribbons inside a dry box; they have no components that are sensitive to moisture. Active ribbons, which have circuitry, might benefit from being kept dry.