Sometimes our team miscalculate their timing and schedules. Therefore, the pigment layer is left for an extended period of time before the base is added. What are your suggestions for "best bonding scenario?"
Civil engineers call this a "cold joint." Sika might have a special product that addresses this but it is probably expensive and not cost effective. What I would do would be to try to make scratches on the surface of the pigmented layer (hopefully they already regularly make scratches when it the pigment layer is wet) and then just pour the backing layer on it. Scratches: long marks (from within 20 mm of one side of the mold to withn 20 mm of the other side) 2-3 mm deep and 2-3 mm wide. Scratches can be spaced about 40 mm apart. If the pigmented layer is already hard then I'd say you have 2 choices: pour the backing layer or throw out the pigmented layer.
Good question. I pray for your success in training people.