'SSIC - Standard Subject Identification Code', All Acronyms, 17 January 2018, <https://www.allacronyms.com/SSIC/Standard_Subject_Identification_Code> [accessed 17 January 2018] Bluebook All Acronyms, SSIC - Standard Subject Identification Code (Jan. 17, 2018, 12:01 AM), available at https://www.allacronyms.com/SSIC/Standard_Subject_Identification_Code. CSE All Acronyms. SSIC - Standard Subject Identification Code [Internet]; January 17, 2018 [cited 2018 JAN 17].
Set your timer for 1 minute and wait. You can keep the etching cream on the glass longer and you will get a more intense etch, but the manufacturer (and I) suggest you start with the recommended 1 minute. When the minute is up, run the glass under luke warm water to remove the etching cream.
I've used clear plastic with good results. But I think you need to leave the glass in place much longer to kill the roots as well. But it would be a good experiment if you left your current work as is and did it again, leaving the glass on for 30 to 45 days. (I did 90 days with the plastic.) Post back please.