There are a number of reasons why some of the black spot have not been killed and turned white. It is mostly due to not enough chemical has been applied to these more stubborn areas, or simply because it hasn’t been left long enough on the surface.
We recommend leaving a minimum of 2-3 hours before rinsing off, but that is only if all the black spots have turned white. NEVER rinse the chemical off before 100% of the black spots have turned white otherwise you will need to start again and apply more product to these isolated areas.
If necessary apply more chemical to the stubborn areas and leave 4 or 5 hours, whatever is necessary to achieve the perfect results.
ALWAYS DO A TEST PATCH FIRST, before applying all the product to your patio or paving areas.
Any problems or questions please contact our technical helpline for further advice 01300-345898