The substrate itself does not need any prep, it is already concrete and happy to accept more concrete (thin-set). However, good idea to cover screw head with piece of A/R mesh tape and put scratch coat of thin-set on top of that. Some adhesives won't like the screw head. By placing the A/R tape on top of screw head with some thin-set mortar we have now made that area the same as the substrate. Any questions drop me a note through maverickmosaics.com website and I will send you a photo. Thanks for your interest!
To Shelley - you asked it you need 2 D-rings, not necessary, especially since you are hanging as a "diamond".
Thank you for this!!! How do you prepare the front side to accommodate your glass tile or does it need any prep???
The substrate itself does not need any prep, it is already concrete and happy to accept more concrete (thin-set). However, good idea to cover screw head with piece of A/R mesh tape and put scratch coat of thin-set on top of that. Some adhesives won't like the screw head. By placing the A/R tape on top of screw head with some thin-set mortar we have now made that area the same as the substrate. Any questions drop me a note through maverickmosaics.com website and I will send you a photo. Thanks for your interest!