Two-Way Humidification System Reviews

One of the easiest humidification systems out there for an acoustic guitar is what is called a two way humidification system.  These are designed to keep the relative humidity inside a case from being too dry or too damp.  Below is an explanation of how these humidifiers work, along with reviews and tips on the most common systems from D’Addario PlanetWaves and Boveda.

How It Works

If the wood of a guitar gets too dry it will shrink and can crack, damaging your instrument.  Conversely, if it gets too damp, the wood will swell and can buckle, also damaging your guitar.  Ideally, the relative humidity should be somewhere in the range of 45-50% to maintain the proper moisture within the wood.  Any system that only adds moisture ultimately neglects how to care for the wood if the humidity gets too high.  Also, any system that removes moisture ends up neglecting what to do if the air is too dry.

two way humidification system                       two way humidification system

One answer to this problem is a system that works both ways.  With that thought in mind, the two-way humidification systems were designed to do just that – to absorb moisture if the humidity is too high, and to release moisture if the humidity drops too low.  They accomplish this with a chemical in gel form, enclosed in a paper-like material that allows moisture to cross back and forth.  When the humidity is too low, the gel gives up moisture so as to raise the humidity in the case.  When the humidity goes too high, the gel will absorb moisture to reduce the humidity.

Since the system works automatically, it eliminates the need to continually have to refill sponges and check humidity levels.  It also does away with adjustments for seasons, temperatures, or even geographic locations.

However, these systems have two disadvantages.  First, it’s easy to put them in a case and forget about them, but they need to be checked periodically to make sure they’re still working.  Failure to do so can be just the same as not having them to begin with.  Second, the gels packs need to be replaced when they cease working.  And that costs money.  The good news is the packs can be rejuvenated, prolonging their life and saving money.  See the details below on how to do this.

Available Systems

There are two systems I am familiar with, one made by D’Addario PlanetWaves and one from Boveda.

D’Addario PlanetWaves

two way humidification system

This system is the first one I was aware of, and is designed exclusively for guitars and basses.  It consists of two pouches, or holders.  The first holds one gel pack and sits in the case near the headstock.  The second holds two gel packs and drops down into the sound hole, thus regulating moisture inside the body.

Recently, D’Addario redesigned the holders, with poor results.  The original holder that sat in the sound hole was made of a porous cloth material that was easy to insert and remove.  Now, however, this holder is made of a rigid plastic that has several problems.  First, it is harder to insert and remove than the flexible cloth holder.  Second, it is quite difficult to get both gel packs into the holder.  Third, closing the holder and making it ready to insert is even more difficult.  And last, and maybe more importantly, for some guitars the holder comes in contact with the back of the body, which has the potential to damage the wood.

D’Addario sells the system in one package, as well as replacement packs.


two way humidification system

Boveda makes humidifiers for a variety of situations, including humidors, instruments, and food packaging.  For all of these, the system is very similar in concept to the D’Addario system above.  The primary difference in the instrument humidifiers, in concept, is that Boveda makes systems for a wide variety of instruments, including violins and cellos.  Even clarinets.  Also, the specs on the guitar system state it maintains relative humidity from 45-55%.

The Boveda holders are a porous cloth material, similar to the original D’Addario holders.  The biggest issue with the Boveda system is the price, being more expensive than the D’Addario system, both in terms of holders and gel packs.

Boveda sells the entire system in one package, but you can also buy the holders separately.  They also sell replacement gel packs.

Rehydrating Gel Packs

The most common situation necessitating replacing the gel packs is when the gel dries out due to extended periods of low humidity.  When this happens, the packs become hard, almost rock-like.  Normally, this is when the packs should be replaced.  But, as I mentioned above, you can rehydrate these dry gel packs.  Here’s how:

  1. Get a plastic container that seals shut.  Something with a flat bottom will work well, even a gallon ziploc bag can work if you’re careful.
  2. Put water in the bottom, maybe an inch deep.
  3. Put the gel packs on something that will keep them out of the water.  DO NOT let them touch the water.  Plastic cups work well for this.
  4. Place the container on top of a heater or in front of a window.  This step is not essential, but the extra heat helps speed up the process.
  5. Monitor their progress and when the gel pack is soft and fluid once again, you’re done!


Here are my recommendations:

Both systems work, and can work well.  So, which one you choose is up to you, based on your preferences and pocketbook.

1.  Do not use the new D’Addario PlanetWave holders.  They’re poorly designed and are more trouble than they’re worth.  At least until they go back to their original design.

2.  If you can find the original D’Addario PlanetWave holders, use them.  This is what I use and I really like them.  One tip on the use of these holders.  Sometimes the edge can get caught on the strings when you remove them from the sound hole.  Instead of inserting it as the directions state, flip it over so the D’Addario logo faces the strings, as opposed to facing away from the strings.

3.  Boveda sells their holders separately, so this is a good alternative to the new D’Addario PlanetWave holders.  One added bonus is the D’Addario gel packs will fit inside the Boveda holders.  (Note that Boveda now makes the gel packs sold under the D’Addario name.)  So, you could get the Boveda holders and the D’Addario gel packs.

4.  Or, you could use the entire Boveda system.  It’s a bit more pricey, but it’s a good system.

5.  Get a hygrometer.  While not absolutely necessary, it can still be a good check on whatever system you decide to go with.

Where To Buy

Boveda System – available from Amazon here.

two way humidification system

Boveda Holders – available here.

two way humidification system

Boveda Replacement Packs – available here.

two way humidification system

D’Addario PlanetWaves Replacement Packs – available here.

two way humidification system

If you have questions or comments, please add them below.

(Note:  As an Amazon Associate, I earn from qualifying purchases.)

Rock On!

2 Replies to “Two-Way Humidification System Reviews”

  1. Gary Robinson says: Reply

    Does the guitar case need to be stored flat to keep the gel packets in place, or does it make no difference.

    1. Hi Gary! It makes no difference whether the case is stored flat or not. I’ve been using the system for years, and I never store a case flat. I don’t have enough space in a my house to do that, so all the cases are stored vertically, and I’ve never had a problem with the gel packs moving around.

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