Hello Avid reader, thank you for the product review in feedback, so it gives me a chance to reply.  Please remember that the word  ULTRAVIOLET in the lower test area is only visible at above 300 µW/cm², which is about 100mJ in 5:50 minutes, so if the letters can’t see the device failed the 300 µW/cm² power test!  If you could see the word ULTRAVIOLET, great, it passed! If not much above 300 µW/cm², it will fade completely in 3 seconds max, more powerful devices up to 15 seconds.   Blessings


In the below picture it gives you an idea of how light the color around the word ULTRAVIOLET is for a passing test when just reaching the min 300 µW/cm²