How to safely remove the black protector in some CPS1 boards

[bubbly]

Hello
Any advice on how to remove all the black thing that covers some of the CPS1 C boards?

This C board I modified as posted in this forum in order to work with CPS1 multi works. But it doesn't look nice so I would like to clean it up without damaging it

 

[RepairGuy95]

Isopropyl 91% will dissolve the glue.
Let it dry for 24 hrs.

 

[bubbly]

Thank you! I'll give it a try