.
Controlling the amount of product applied on
roughened quartz plate is difficult to achieve because of the low
adherence of the sunscreen.
Self-standing Transpore tends to break
down and, for this reason, it is used coupled to a smooth quartz
plate; this results in lower transmittance values. Not all substrates
were photo-stable and only PMMA plate and roughened quartz
plate can be recommended for photo-stability tests. PTFE also
showed to be suitable for photo-stability tests and can be regarded
as an alternative option.