just been reading up about it and this is one thing i found on how to maintain the self cleaning glass and this come from Pilkington, one of the leading glass suppliers in the UK Tips for Maintaining Self-Cleaning Glass The coating on Pilkington Activ™ self-cleaning glass products needs approximately 5 - 7 days to energise. After this period it continues to work even on cloudy days and during the night, washing away dirt whenever it rains. However, there are certain circumstances in which a little basic maintenance on self-cleaning glass may be necessary. Heavy Dirt Deposits The coating on self-cleaning glass normally breaks down even the heaviest deposits of organic dirt in time - but if the surface is so dirty that daylight cannot reach the glass, the self-cleaning action will not take effect. In such extreme cases, you will need to clean the glass with warm soapy water and a soft cloth. After a few days the self-cleaning process will have re-activated. Maintaining During Dry Spells During very dry spells you may need to speed the window cleaning process up as there will have been no rain to wash loosened dirt away. This is easily done by simply hosing the glass down with water - which should remove most traces of dirt. Note: organic dirt will not necessarily be removed by hosing, so some dirt may still be seen when the glass dries after the hosing treatment. Maintaining the Coating Tests have shown that the special coating on the self-cleaning glass will not flake off or discolour, but it will be affected if the surface itself is damaged; for example, by pointed objects or abrasive cleaners. For this reason, ink or paint must be carefully removed from the self-cleaning glass using a soft cloth and methylated spirits and never with harsh scouring glass cleaning agents, steel wool, razor blades or anything else that would scratch the glass.