Ever fished out those little packets from a new camera bag and thought, “What on earth is Silica Gel?” Well, buckle up, because we’re about to dive into the wonderful world of these moisture-munching marvels! You might think they’re just pesky packaging, but let me tell you, Silica Gel is about to become your camera gear’s new best friend.
So, what is Silica Gel, exactly? It’s like a super-sponge for humidity, sucking up moisture faster than you can say “fungus on the lens.” In this article, we’re going to unpack the mystery of these tiny tech saviors. Whether you’re battling foggy lenses, or trying to preserve your vintage camera collection, Silica Gel is the unsung hero you never knew you needed. Stick around, and you’ll soon be singing the praises of these little moisture-zappers to anyone who’ll listen!
What Is Silica Gel?
Silica gel is amorphous Silicon Dioxide, also known by its chemical formula SiO₂. It’s made from sodium silicate and sulfuric acid. It’s a relatively inert substance that is highly porous, with a high capacity to adsorb material. It can adsorb up to 37% of its weight in water vapor, depending on the specific formulation.
Silica gel is also resistant to mold and bacteria. While Silica Gel itself is non-toxic if ingested, it often contains added moisture indicators (like cobalt chloride) that can be harmful if consumed in large quantities. Therefore, packages often carry “do not eat” warnings.
Silica gel is available in different forms: beads, granules, and powder. For photographers, I would suggest using the beads as they’re the least likely form to leave a powder residue.
As mentioned, Silica Gel is an adsorbent – a substance that removes moisture from the air. It can be used to maintain low Relative Humidity (RH) in an enclosed space – that’s what we’re interested in, right.
In this way, it prevents fungus growth on camera lenses. Over time, the beads or granules become saturated with the moisture that it has adsorbed, and lose their ability to continue removing humidity from the air. At this point they need to be recharged by careful re-heating and subsequent cooling of the beads.
Silica Gel can be reused many times, in this way, and continues to work with high efficiency, even after hundreds of reuses.
Types of Silica Gel:
You can get Silica Gel beads in a few different types:
- White, non-indicating Silica Gel
- Blue to Pink Indicating Silica Gel
- Orange to Green Indicating Silica Gel
We suggest using the orange-green indicating silica gel beads. This is a good option for a number of reasons.
- It’s easy to know when it needs to be recharged
- It’s less toxic, and safe to be used at home
- Usable in a comfortable temperature range
How Much Moisture Can Silica Gel Remove From the Air?
Silica Gel is very efficient at pulling moisture out of the air. It can adsorb up to approximately 37% of its own weight in moisture. This means that every 1,000 grams of Silica Gel can adsorb up to 370ml of moisture from the air around it.
Note that color-indicating Silica Gel changes color when it has gained 8-10% of its weight in moisture. Even if the color changes at 8% of its weight, Silica Gel will continue to adsorb moisture up to 37% of its weight. This gives you a good buffer, so don’t worry if the color of the indicating silica gel has just changed. It’s probably still absorbing moisture even after the color changes, but don’t wait too long.
How Efficient Is Silica Gel at Removing Moisture?
At room temperature and high humidity, Silica Gel is remarkably efficient at removing moisture from the surrounding air. It is more efficient at removing moisture from the air at higher humidity levels than at low humidity levels.
- Silica Gel will reach maximum saturation in about 5 hours at 25°C and 77% RH.
- As long as the Silica Gel is not saturated, it can reduce RH (Relative Humidity) to less than 40% RH.
This means that you will get a better result by using more Silica Gel in your dry box, rather than less. I use about 4.5 lbs for a box that is about 6 cubic feet in size because it is quite cheap.
Quick TIP: You can keep track of how humid your camera storage box is, by using a Digital Hygrometer. I highly recommend using one.
Testing How Long Silica Gel Needs To Be Dried
In my “extensive” experience with drying Silica Gel (maybe I should put that on my résumé?), I have noticed that there’s little point in drying it for more than 2 hours. To get some actual proof, I decided to accurately measure the weight of two batches of Silica Gel that I was drying.
Testing Methodology
Each batch was over 500grams in total, and I weighed each batch before heating, and after 1 hour, 2 hours and 3 hours of heating, each.
Drying Duration Results
As you can see, there is between 14.6%-16.3% change after one hour. After 2 hours, the percent change has reduced significantly to just 4.2%-4.3%. And after the third hour, there’s hardly any change, at just 0.8%-0.5%.
The actual weight reduction ranged from 19.6% after 3 hours for Batch 1, to 21% for Batch 2 when compared to the starting weight.
| After 1 hour | After 2 hours | After 3 hours | |
| Batch 1 | 14.6% | 4.2% | 0.8% |
| Batch 2 | 16.3% | 4.3% | 0.5% |
So, it turns out that the Silica Gel was carrying over 19.5% of its own weight in stored water (over 130 grams). After heating it for 1 hour, there was a significant reduction in stored humidity, and less reduction after 2 hours. However, the 3rd hour yielded minimal change, and as a result it is not economical to go on heating the beads for longer.
Hence, our suggestion to dry Silica Gel for at least 1 hour, and at the most, 2 hours.
How Much Silica Gel Do You Need for Your Dry Box?
Silica Gel quickly absorbs moisture and can hold up to 40% of its weight in water. To keep the level of relative humidity consistently low, it is advisable to use more than may be required.
Silica Gel reduces the humidity of the air to around 40% RH (Relative Humidity), but does not go much below that level.
To calculate how much water must be removed from the atmosphere, we must first know how much is present, then we can calculate how much Silica Gel would be required to remove it. We can do this easily with a Relative Humidity (RH) to Absolute Humidity calculator.
With such a calculator, we can easily calculate how much water is in the air when the Relative Humidity and air temperature are known (easily done with a hygrometer). Then, we can calculate the difference between the current RH and the ideal RH (40% or so), to arrive at the amount of water to be removed, and from there, how much Silica Gel is needed.
Calculation Example:
At an air temperature of 25 °C and Relative Humidity of 75%, there will be about 17.2 grams of water per cubic meter.
In contrast at 40% RH, and the same temperature there will be only 9.2 grams per cubic meter. The difference is about 8g/m3. In this situation, one would need at least 20 grams of Silica Gel per m3 to reduce the relative humidity to 40%, and ideally, one would use more to ensure that any humidity that seeps in is kept under control.
Wrapping Up
Well, there you have it! Silica Gel might not be the most glamorous item in your camera bag, but it’s certainly one of the unsung heroes of gear preservation. This humble moisture-absorber is a real asset for keeping your prized lenses and bodies in top condition, especially if you’re fond of shooting in challenging weather conditions!
Remember, a few packets of this stuff can mean the difference between crystal-clear optics and a fungi-infested nightmare. It’s inexpensive, reusable, and with those handy color-changing varieties, you’ll know exactly when it’s time to give it a quick refresh in the oven.
So, next time you’re packing for a shoot or storing away that expensive piece of equipment, don’t forget to throw in some Silica Gel. Your gear (and your wallet) will thank you in the long run. Happy shooting, and keep those cameras dry!
