Why Your Leather Feels “Sticky” in High Humidity
In climates where humidity is persistently high, it is common to notice surface changes in organic materials such as leather or wood. You might assume the leather has poor quality, is old, or has been damaged. In most cases, the issue is not the material itself. The cause is the environment.
In tropical climates such as Singapore’s, relative humidity often remains at levels that change how materials interact with moisture. Understanding this behaviour helps explain why leather can feel sticky, develop odours, or even show early signs of mould without being defective.
Leather and Moisture: How They Interact
Leather is an organic, porous material that naturally absorbs and releases moisture. The rate at which this happens depends on the moisture content of the air around it.
Indoor air with high relative humidity contains more moisture. When leather is exposed to that air over time, moisture transfers into the material until it reaches a balance state known as equilibrium moisture content. The higher the ambient humidity, the more moisture the material holds at equilibrium.
In environments where relative humidity commonly sits above 70%, moisture absorption outpaces release. The material holds moisture for longer periods. Over time this changes the tactile properties of the surface.
What High Humidity Does to Leather
When leather absorbs moisture:
The surface becomes slightly tacky or sticky to the touch
The feel of the leather changes from dry and stable to damp and heavy
Odours can develop as moisture interacts with organic fibres
These effects are directly related to how humidity influences the material’s internal moisture balance, not a reflection of quality or age.
In Singapore, average outdoor relative humidity frequently ranges between 70% and 90%. Indoors, humidity levels remain elevated unless actively controlled. Air-conditioning systems are designed primarily for temperature control. They reduce dry-bulb temperature but do not always remove enough moisture from the air to keep relative humidity low. This leaves spaces that feel cool yet remain humid because moisture is not being actively removed.
Mould Growth Is an Environmental Response
Another common misconception is that mould on leather is caused by poor material or neglect. In reality, mould growth is a response to environmental conditions, not a defect of the leather itself.
Mould spores are present in indoor air at all times. They require:
A source of moisture
An organic substrate to feed on
Suitable temperature conditions
When relative humidity is high for prolonged periods, moisture within the material increases. The surface and internal fibres provide conditions that support spore germination and growth. This is why organic materials such as leather, wood, or textiles can develop mould even when they are new or well cared for.
Controlling humidity is the key to preventing this process, not just cleaning the surface after growth appears.
Why This Persists in Tropical Climates
In Singapore and similar climates, elevated humidity is a baseline condition, not temporal - and warm air can hold large amounts of moisture. As outdoor air moves indoors through ventilation, infiltration, or daily activity, that moisture accumulates if it is not removed. Air-conditioning alone seldom addresses this because it is optimised for sensible cooling, not moisture removal. Spaces may feel cool, yet humidity remains high. Over time, elevated humidity becomes cumulative, not cyclical, leading to ongoing moisture absorption in materials.
How Humidity Control Protects Materials
Preventing leather from feeling sticky or developing mould is not about changing the material, but stabilising the environment.
Effective humidity control reduces indoor relative humidity to levels where the equilibrium moisture content of materials remains low and stable. This prevents excessive moisture uptake in leather and other organic materials.
In environments where humidity is stabilised, materials remain closer to their intended moisture balance. Leather stays dry to the touch. Surfaces remain stable. The risk of mould growth is significantly reduced.
This is why humidity management is treated seriously in industrial and commercial settings where material performance matters. It’s not just about comfort - it’s protection.
Practical Steps for Control
Assessing actual humidity behaviour in a space is the starting point. A professional humidity assessment helps determine:
How humidity fluctuates over time
Sources of moisture ingress
The moisture balance relative to material behaviour
Once these factors are understood, solutions can be specified and deployed to maintain stable relative humidity. This approach ensures materials such as leather do not absorb excessive moisture and remain in a condition suited to their use.
Humidity control should be part of the design and ongoing environment management strategy, not an afterthought.
