Silica gel vs So Sponge (AS-B): best desiccant for IP boxes
In an IP waterproof electrical box, humidity can become a critical problem. Even in a sealed electrical housing, internal condensation can appear during rapid temperature variations.
What is the best anti-humidity product to effectively protect your equipment?
We compared two solutions in the laboratory:
- So Sponge (high-performance mesoporous adsorbent)
- Silica gel
Why is humidity a risk in an IP box?
An outdoor electrical box or IP waterproof housing is not completely isolated from air humidity. When confined humid air experiences sharp temperature drops, the dew point can be reached, resulting in condensation and liquid water formation on components.
This condensation in electrical boxes may cause:
- Corrosion
- Short circuits
- Premature component degradation
- Loss of reliability
A quality anti-condensation product must ensure genuine humidity control, even under extreme conditions.
Laboratory test protocol
Setup
Three IP65 waterproof electrical boxes equipped with humidity sensors were tested:
- Empty case (no moisture absorbent)
- Case with 1 g of So Sponge
- Case with 1 g of silica gel
Both adsorbents were preconditioned in the laboratory atmosphere.
Simulation of a critical environment
To generate very high relative humidity, a cup containing 1 g of water was placed in each case. After 3:30 minutes:
- Water beakers at 15°C were placed on the boxes
- This created a cold spot
- This simulated rapid surface cooling
This scenario reproduced real conditions of an outdoor electrical box subject to significant climatic variations.
Results: measured relative humidity
The humidity indicator showed that:
- The box containing So Sponge maintained significantly lower relative humidity
- The box containing silica gel reached near-saturation levels
Silica gel quickly loses effectiveness when humidity becomes very high.
Observation of condensation
Results showed:
- Condensation visible in the empty box
- Condensation visible in the box containing silica gel
- No condensation in the box containing So Sponge
Silica gel saturates rapidly and loses humidity control effectiveness once saturated. So Sponge maintains high adsorption capacity even at high ambient humidity.
Why is silica gel limited?
Silica gel is a conventional desiccant that works properly at moderate humidity but at very high humidity:
- Fast saturation occurs
- Efficiency is lost
- Condensation risk increases
This behaviour is consistent with published adsorption isotherms: above roughly 70% RH, silica gel approaches saturation (a plateau around 35 to 40% of its weight in water), so its residual buffering capacity drops sharply (Sorbent Systems; Thomson, WAAC).
Anti-humidity bags based on silica are sized for small volumes and are not designed for environments subject to severe thermal cycles.
Why is So Sponge a better anti-humidity product?
Unlike silica gel, So Sponge offers:
- Strong adsorption capacity at high relative humidity
- Maintained hygrometric control in extreme conditions
- No sudden saturation
- Solutions adapted to outdoor waterproof electrical boxes
It acts as a passive humidity controller, avoiding critical condensation thresholds.
Test summary
| Criterion | Silica gel | So Sponge (SRD) |
|---|---|---|
| Absorption at moderate humidity | ✓ | ✓ |
| Absorption at high humidity (> 70% RH) | ✗ saturated | ✓ |
| Condensation observed during test | Yes | No |
| Regeneration | No | Self-regenerating |
| Maintenance | Regular replacement | Zero |
| Lifespan | A few months | Unlimited |
Conclusion: which anti-humidity product should you choose?
For an IP electrical box, especially outdoors:
- Silica gel may suffice in stable environments
- In severe conditions with high humidity and rapid cooling, it becomes ineffective
- So Sponge provides long-lasting protection against condensation
The AS-B labels prevent condensation in IP boxes subject to extreme weather conditions. Unlike silica gel, they maintain high adsorption capacity at very high humidity levels.
Choosing your anti-condensation desiccant
For a sealed electronics enclosure, the decision comes down to maintenance access: a reusable or rechargeable desiccant needs periodic oven reactivation, while the self-regenerating AS-B sticker works in place for the life of the equipment.
→ See AS-B formats and pricing (XS to L) · Calculate ROI on your fleet
Further reading
- Reusable & rechargeable desiccant: which truly lasts?
- Gore Vent & breather vents: do they stop condensation?
- AS-B Sticker product page — XS/S/M/L formats
Sources
- Sorbent Systems — Desiccant adsorption charts: silica gel isotherms, maximum capacity ~40% of weight.
- G. Thomson — An Evaluation of Silica Gel for Humidity Control, WAAC Newsletter: collapse of buffering capacity near saturation.
