The Rubbing Test is a quality testing procedure refering to the adhesivity and conformity checking of solar product labels.
What is the purpose of the Rubbing Test?
Solar panels and inverters are exposed for many years to environmental conditions that - depending on the geographical location of the installation - be harsh and result in bad quality labels and serial numbers attached to these solar products to become unreadable.
In such case, a worn of label and serial number may in worst case impact the warranty terms of that product as it cannot any more specifically be attributed to the supplying manufacturer.
Moreover, in a large installation, a non-readable serial number makes it hard to track that individual system component and render pre-shipment and post-installation performance data comparison nearly impossible.
How is the Rubbing Test performed?
Through the rubbing test, PV quality auditors make sure that the label and the serial number at the back of a solar product, particularly solar panels and solar inverters, will still be readable after 25 years.
It includes 15 seconds of rubbing on the label and on the serial number, with a mix of water and alcohol. Quality labels and serial numbers will be printend/ produced using a protective coating so that even hard rubbing will not rub away any text, warranty descriptions or certification logos.
Bad quality labels, which are one of the favorite small quality saving details for manufacturers to cut some costs are usually printed with standard office printers with the dried content of that labels and serial numbers easily rubbed away under the impact of liquids (in real world scenarios: rain).