Cracking of 1.6 tinted lens duiring HC process.

[shubhendu]

Hello.
I have suffered by the cracking issue coming during the hard coat process particularly in 1.6 index,any advice will be very helpful .

[Mauro.Airoldi]

some questions:
1 Do you mean that the cracking of 1.6 appeared during the curing of the lenses in the oven or after days?
2 what curing times and temperatures do you use?
3 Does the break only affect the HC layer or has it spread to the lens surface?
4 does the HC have index 1.5?
let me know
Mauro

[shubhendu]

Ans 1- cracking appear before curing in the oven.
Ans 2- in general 2.5 hrs@125 degree
Ans 3- it's spread to the lens surface
Ans 4- no it's not 1.5,we used 1.6 index varnis for 1.6 index lens & it's only used for 1.6.we have different varnish for 1.5 index.

[Mauro.Airoldi]

I would check the temperature of the pre-drying ovens the lenses must not exceed 60/70 ° c
check the thickness of the HC, for a colorable 3-4 microns
Try treating 1.6 with HC 1.5 to see if the same problem occurs

[shubhendu]

Thanks for your valuable tips.
After dipping in 1.6 varnish it's going to pre- drying oven with 80* temparature.

[Mauro.Airoldi]

the drying and curing temperatures depend on the type of HC, the type of substrate, the thickness deposited and whether or not a primer is used.
In general, my experience with colorable HC gives me temperatures around 70 ° for drying and 110/120 ° c for polymerization (2-3 hours).
if the drying phase after deeping in HC is too fast or hot you will have tension on the surface.
Try posting some pictures of the problem

[shubhendu]

Picture send.

[Mauro.Airoldi]

seen from the photos they are not cracks but scratches, given the position I would say caused by the tools you use to load the lenses (tweezers).

[shubhendu]

Noted sir,I,ll take care of those point adviced by you in future..
Many many thanks for your time & suggestions.