The Festoon Guys, for the lovers of fine festoon & vintage bulbs.
The Festoon Guys, for the lovers of fine festoon & vintage bulbs.
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Bulb Condensation


Condensation in your bulb

Moisture in your bulb? There are two very different causes for this. The first is condensation, which may naturally occur in any bulb, and not suggestive of a defect or hazard. The second is water ingress, or a leak into the bulb which may cause system failure. The following explanation clearly describes the difference.

Nearly all bulbs are prone to condensation because:

    • air is trapped inside a bulb when manufactured - the plastic parts used in bulbs naturally absorb moisture in the air, so as the bulb heats up, these plastics parts release moisture that mixes with air. The moisture attaches itself to the coolest part of the bulb 
    • halogen bulbs tend to run hot so the moisture evaporates faster
    • LED bulbs produce less heat, taking longer for moisture to evaporate

    Condensation is the change of water from a gaseous form (vapour) into liquid water. It appears as small droplets of moisture inside the bulb. Condensation does not cause a problem with normal operation of the bulb and is therefore NOT considered to be a defect or warrantable condition. In fact, The Festoon Guys bulbs are designed to allow moisture to escape and not reenter, but it takes time for the moisture to evaporate (the amount of time will depend upon whether or not the bulb is turned on or not).

    Water Ingress describes water that leaks into a bulb, appearing as large droplets and pooling of water that is clearly visible. Sources of water ingress can vary. If a bulb suffers water ingress as the result of physical abuse and/or misuse, it would not constitute a manufacturing defect. Otherwise, water ingress caused by a defect in workmanship is a warrantable item. In the event of a possible defect, please contact us to arrange a replacement at

    Water Ingress