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Humidipak Waterless Humidity Control System

By Todd Stuart Phillips

Insufficient humidity can ravage expensive acoustic guitars. It is important for guitarists to provide an environment that will protect their instruments from becoming too dry. But typical guitar humidifiers can be messy and must be monitored often to make sure they do not dry out or over humidify a guitar. Fortunately, the new Planet Waves Humidipak System has arrived to alleviate all humidification concerns for the discriminating guitarist.

The products of Humidipak, Inc. have revolutionized the task of humidity control for a variety of industries, from the storage of priceless, fine art to the packaging of food, wood and paper products, and even expensive cigars. Now they have teamed up with Planet Waves to bring this important technology to the owners of fine, acoustic guitars. This hi-tech, lo-maintenance system is the first of its kind and provides a no mess, year-round solution to humidification. There may never be a better way to go.

The entire system consists of just three, soft pouches placed inside the guitar case. One pouch goes under the headstock of the guitar. The other two are connected and hang down inside the guitar's body like saddlebags; suspended by the two center strings. Each pouch holds a special Humidipak "packette" which is the key to the humidity control. The packettes require no maintenance whatsoever. The only thing left to do is close the guitar case and wait until the packettes need to be replaced - some two or three times a year.

That is all there is to it. There is no watering required, as with typical guitar humidifiers. So there is no dripping, no wiping off, no staining the unfinished wood inside the guitar. There is no guesswork as to how much humidity is too much, or not enough. Normal guitar humidifiers continue to add humidity whether the guitar needs it or not. Humidipak's three-pouch system adds moisture or takes it away as necessary to maintain a relative humidity of 45% inside a closed guitar case.

How does it work?

Each packette is filled with a solution of purified water, natural salt and a sterile gum thickening agent. The packette is lined with the same kind of semi-permeable membrane used in water purification systems, which allows hyperfiltration, otherwise known as reverse osmosis. Pure water ions pass back and forth through the membrane in the form of vapor, but liquid water and the larger ions of salt and gum are blocked from leaving the packette. 

That means the Planet Waves Humidipak system is the world's first 2-way humidifier for acoustic guitars. If the humidity inside the case falls below the target level, water vapor is released from the saturated salt solution. If the humidity levels climb above the target level, the solution reacts and water is absorbed into the packette from the air inside the case. The amount of moisture exchanged is dictated by the principal known as Raoult's Law, which demonstrates how water inside a sealed container will evaporate from a solution until the amount of water ions in the air equals the number on the surface of the liquid and how that amount can be controlled by infusing a certain quantity of solvent into the solution. So long as the lid remains closed, the humidity inside the container quickly stabilizes at the desired equilibrium. For a cigar humidor, it would be near 75%. For a guitar case, a different amount of solvent is added so the humidification stops at the desired amount of around 45%.

According to the manufacturer, the Humidipak system is designed to achieve a +/- 1% accuracy. It also provides purified water vapor, eliminating the chance that minerals or other impurities found in tap water will invade the environment. Since there are no sponges or other damp material in contact with the air there is no risk of mold or mildew and the frequent soaking of humidifiers will become a thing of the past.

That all sounds wonderful. How does it work in real life? To find out, I employed three different hygrometers and a couple different guitar cases. I calibrated two digital humidor hygrometers with the high-quality nautical hygrometer in my Teel Guitar Works Weather Station, by inundating them in a bathroom during a hot shower. I noted the variance in readings and then let all three of them sit in an empty guitar case for 24 hours before checking again.

I then put my 1998 Martin OM-28V into the case with one remaining hygrometer and installed the Planet Waves Humidipak system. Within 48 hours the humidity had stabilized at 47%. I checked the readings once a day, during a week that saw temperatures ranging from 56 F to over 90 F and humidity levels which rose and fell dramatically. The level in the case remained between 45% and 48%. 

I took the guitar out of the case and put the larger weather station in with the two digital hygrometers and waited to see what changes might take place when there was more air in the case due the guitar's absence. The readings reached as high as 52% over the next two days but never went below 47%. All well within acceptable limits, even without considering margins of error.

I then moved the system into a different kind of guitar case, with a different size guitar made from different woods. The results were practically identical, with an average reading of 48% and an overall span of 4% flux over the course of several very hot, humid days. Since then, a cold front has moved into the area and the humidity dropped to 35%. The air inside the guitar case has remained at or slightly above 45%.

The system worked as advertised. I cannot imagine a more error-free, easy to use product when it comes to humidifying a guitar case. So, are there any drawbacks to this system? That depends on one's perspective.

I would say this product is not for everyone, based on monetary reasons. The complete system costs more than basic guitar humidifiers. But where those humidifiers require no further investment, this system requires ongoing costs in the form of replacement packettes, in perpetuity. Planet Waves claims the packettes will last between two to six months before they become hard and need replaced. How long they last would be based on several factors, including how often the case is opened and how close to a vacuum seal the case provides. Currently they sell for about $7 a packette. When used year-round, the best case scenario means a $21 investment twice a year, or $3.50 a month. Worst case goes up to $21 six times a year, or $10.50 a month. Not everyone will be willing to pay that kind of money. 

However, for people who have spent thousands of dollars, or even tens of thousands on an acoustic guitar, the peace of mind that would come with a humidification system this foolproof should prove more than worth the investment. And the attractive, black pouches themselves are unobtrusive and seem right at home in a fancy case housing one of the world's best guitars. That right there gives them a major advantage over the plastic soundhole humidifiers or the extremely unattractive rubber and sponge varieties that look like something stolen from a dilapidated medical clinic. Also, the more expensive the guitar the higher quality the case. Cases that are relatively airtight should provide a better environment for the packettes to work at maximum efficiency, dropping replacement costs considerably. This system would also be ideal for collectors who often leave museum quality instruments in their cases for weeks at a time.

How much that peace of mind is worth to you will be a personal choice. Someone living in Utah or Arizona might go through packettes quickly. Then again, they might prefer that to cracks, loose binding or seam separations. I have yet to see a Martin guitar in an Arizona bar that did not have one or the other, due to the arid climate. Someone in the humid Northeast may find they only need to use the system in the winter. Those living in the extreme humidity of the Deep South may find they need to purchase the special Hi-Absorption Replacement Packette and use it year round. These are specially designed packettes that have a greater absorption rate than the normal packettes. 

In general, I suspect the packettes will have to be replaced at the start of the dry, winter months but that they will last longer in the humid, summer months. I intend to find out, so you may want to return to this column in July to see if my new packettes are still going strong.

So, I shall continue to keep a guitar in that case to find out just how long these packettes really last. But I do not think the system will prove overly expensive. I live in Brooklyn, where the humidity rarely drops below 40% from May to October. I often leave my guitars out on stands as it is. I will therefore only use the Humidipak system when the heat kicks in and all the moisture goes away. Someone else who is diligent about keeping their guitar in its case when not in use will likely get a good lifespan out of the packettes regardless of the time of year. Given how often I have opened a case to find the traditional humidifier dry as a bone, I think many people will agree that this system is relatively short on expense and long on peace of mind.

The Planet Waves Humidipak Acoustic Guitar Humidification System is well thought out and presented in an attractive, easy to use manner. It does what its maker claims, by providing a consistent relative humidity, free from impurities and mess, effortlessly doing its job for weeks at a time. That would be enough to earn the highest rating. However, the product requires ongoing financial investment in the form of replacement packettes. As such, not everyone will feel they need to pamper their musical instrument to such an extent. That being said, those willing to pay a little more will definitely find this product everything it claims to be.

Out of a possible 8 Notes on the T Spoon Scale of Guitaracity I give the Planet Waves Humidipak Acoustic Guitar Humidification System a hi-tech but lo-maintenance 7 Notes.


UPDATE 8/1/07:
Well it is now well over two months and the Humidipak packettes are still going strong. The hygrometer read 47.5% and the packettes are slightly less puffy then when I put them in, but a long way from solidified gel, which is the signal they need to be replaced. I expect them to last at least another two months if not longer.

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Humidipak Guitar Humidifier reviews

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