Observed today a moldy film on the surface of the distilled water with 1 cap-full of hydrogen peroxide that began testing on Feb 3rd.  In looking back at the update on April 19, the film was present at that time, meaning the film was present about 10 or fewer weeks into the testing. However, the filament continues to work fine. This data strengthens our recommendation to use 3 to 5 cap-fulls of 3% hydrogen peroxide with each reservoir fill. 

The filament with 1 cap-full of peroxide in distilled water, initiated on Feb 3rd, appears to have increasing pinkish discoloration in the loop area (bottom left in photo), but still not severe after more than 75 days of testing. The filament with 2 cap-fulls of peroxide in distilled water (bottom right in photo), also in testing more than 75 days, continues to show no sign of discoloration, as do the samples with increasing amounts of peroxide that began testing earlier this month. 

Removed the tap water, distilled water and distilled water with rubbing alcohol filaments, and continuing testing with previous distilled water with cap-fulls of 3% peroxide. These each had about 1.5 to 2 cups of distilled water, which translates to the filament with 1 cap-full of peroxide having less than 1/2 cap-full of peroxide per cup, and the filament with 2 cap-fulls of peroxide having more than 1 cap-full of peroxide per cup. Two new filaments have  exactly 2 cups of distilled water with 3 cap-fulls (1.5 cap-fulls of peroxide per cup) and 4 cap-fulls (2 cap-fulls of peroxide per cup). For reference, the last filament has only 3% peroxide.  Summarized here:

1. <1/2 cap-full peroxide per cup 
2. >1 cap-full peroxide per cup 
3. 1.5 cap-fulls peroxide per cup
4. 2 cap-fulls peroxide per cup
5. 100% peroxide

 It's probably worth noting again that previous testing has been completed inside a closed container, in a 100% relative humidity environment, meaning all testing is under worst case conditions - except for lighting. In the container, no UV light is present to catalyze the reaction and decompose hydrogen peroxide. Going forward, samples have been inserted into a cigar humidor with a glass top open to room lighting. I'll monitor and report periodically. 

Upon closer examination in bright light, the filament in distilled water with 1 cap-full of peroxide at beginning of testing has a pinkish tint, while the filament in distilled water with 2 cap-fulls of peroxide at beginning of testing does not. This pinkish discoloration is faint, but likely a sign of mold formation. By contrast, the filament with 2 cap-fulls of peroxide appears as white as it did at the beginning of the testing. Next testing will likely be investigating the optimum amount of 3% peroxide to add to distilled water to eliminate or reduce mold formation and extend the life of filaments.

The 3% hydrogen peroxide samples continue to look pristine, with no signs of filament discoloration since we began testing on Feb 3rd (7.5 weeks) at 99% RH. We are declaring peroxide the clear winner in this testing and will be recommending going forward. 
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No changes, but we are amazed the filament in the tap water containing a copper penny is still total free of discoloration after 18 days. 

Allowed filament is soak in white vinegar over night on March 5th, rinsed thoroughly with water, and inserted into reservoir. There is now water flow into the loop end of the filament, but it is noticeably less than through a new filament. So, soaking in partially effective at restoring dried out filaments. 

We're sure most of our customers would be interested in extending the life of their filaments, although some simply replace them on a routine schedule. We would like to understand why a filament after being wetted and allowed to dry out, seems to have little water transmission or  stop working altogether. One observation is that the dried out loop tends to have some discoloration, which might point to some form of microorganism grew there - and possibly died there - after the water stopped reaching that area. This organism or its residue may reduce the water transmission to the point the filament can't keep up with the demand and simply dries out. Another possibility is that there is mineral deposit forming in the area, also reducing the water transmission to the point the filament can't keep up with the demand and simply dries out. 

In the Mold and Mildew Test initiated in early Feb 2020, we're not seeing any discoloration of the samples containing 3% hydrogen peroxide, leading us to believe the discoloration is mostly from micro organisms. We would not expect peroxide would control mineral deposits  - or that distilled water would contain much in the way of minerals. 

So, we've allowed a filament to dry out, and confirmed there is no water transmission in the discolored portion of the filament loop. We just began soaking in distilled white vinegar, which consists of 5 to 8% acetic acid (CH3COOH), water and trace amounts of other chemicals, and know to kill bacteria and viruses. We'll observe whether the discoloration is reduced or eliminated, and then re-test the filament.  

The discoloration on the tap water only and distilled water only has not worsened. And the addition of 3% hydrogen peroxide to these samples recently has not reversed the discoloration. The rubbing alcohol samples have about the sample discoloration as reported previously - not noticeably worse. The original distilled water samples with 3% hydrogen peroxide added still look as clean as at beginning of testing on Feb 3rd. The tap water sample containing the copper penny shows no change at Day 4. 

We recently switched the HumiForm Cigar Humidifier filament tubing from painted PVC to copper. In doing so, we learned about copper properties in reducing micro-organisms. There appears to be a long history of using copper as a way of reducing mold growth for containers holding water, although the mechanism doesn't seem to be well understood. For curiosity, I've added a new container of tap water with a filament, and dropped a penny inside today. Will begin monitoring and reporting along with previous containers and filaments. 

Evaluating a larger diameter filament to help customers in particularly dry environments, as an alternative to purchasing a second reservoir.

No change. Since adding 3% hydrogen peroxide to the tap water and distilled water samples, the mold growth has not worsened or reversed. The original samples with distilled water and 1 and 2 cap-fulls of 3% hydrogen peroxide are still free of visible mold. We also have other customers reporting success with adding hydrogen peroxide. We'll continue the test to see if and when this changes.

Pulled white vinegar containers from the overall testing since the filaments were beginning to exhibit mold specks, and due to the odor. Other containers appear to be unchanged from last reporting. 

No sign of discoloration. Humidity still reading at 99% RH.

75 hours  after initiating the test, the hygrometer continues to read 99%. There is no sign of discoloration yet. The smell of white vinegar is very strong - and it's likely no one will want this as an option. I'll leave the two vinegar containers for now. 

I opened the cooler and inserted a hygrometer. A slight odor of the white vinegar was noticeable. About an hour later the relative humidity is around 92%. This is likely the result of 7 filaments being in use at the same time, the cooler volume being smaller and its seal being better than in a Musik Tent enclosure. This elevated humidity should accelerate the testing.  Checked a few hours later and hygrometer was up to 97% RH.  Later in day, the  inside of the cooler has climbed to 99% RH. 

In order to test various mold and mildew inhibitors, we filled up 7 containers with 1.5 cups of water each as follows:

• Tap water only
• Distilled water with 1 capful of hydrogen peroxide
• Distilled water with 1 capful of rubbing alcohol
• Distilled water only
• Distilled water with 1 capful of white vinegar
• Distilled water with 2 capfuls of white vinegar
• Distilled water with 2 capfuls of hydrogen peroxide

We placed 10" long filaments, folded in half, into each container and closed all 7 containers inside a cooler.