During a routine Electrical Installation Condition Report inspection in Cornwall, we discovered 'green goo' - a characteristic sign of aging PVC cables from the 1960s-70s era - affecting multiple circuits throughout the property.
Our electrical inspection revealed an issue commonly found in properties with older electrical installations, particularly those from the 1960s and 1970s. During what began as a standard EICR inspection, we identified several instances of ‘green goo’, a phenomenon that occurs when plasticiser chemicals from old PVC cable insulation interact with copper conductors.
The history behind this issue dates back to a significant change in electrical installations during the late 1950s and early 1960s. During this period, the electrical industry transitioned from rubber insulation to PVC insulated cables. This switch happened because PVC offered more practical benefits and could be manufactured in large quantities as needed, making it an economical choice for domestic electrical installations.
However, the early formulations of PVC insulation included a plasticiser chemical that wasn’t chemically bonded into the mixture. This plasticiser was essential for maintaining the cable’s flexibility – unlike modern uPVC pipes which are unplasticised and rigid. As electrical current flows through the conductors, it creates thermal cycling – heating and cooling of the cables. This temperature fluctuation causes the plasticiser to migrate towards the copper conductor’s surface.
In vertical cable runs, such as those to switches and socket outlets, gravity gradually draws this substance downward over the years. The characteristic green colour develops because the migrating plasticiser dissolves tiny amounts of copper from the conductors. Higher ambient temperatures in the property can speed up this process, which explains why we often find more significant deposits in warmer areas of buildings.
The inspection uncovered this conductive substance particularly around switch boxes and electrical outlets. This type of discovery provides valuable insight into the age and condition of electrical installations within properties of this era. It’s particularly common in domestic properties that underwent electrical installations during the significant housing developments of the 1960s and 1970s, before cable manufacturers reformulated PVC compounds to prevent this issue.
Regular electrical inspections play a vital role in identifying such historical installation issues in domestic properties. Properties from this era often contain these original PVC cables, making periodic electrical inspections particularly important for homeowners of properties built or rewired during this period.
