Removing glue from shower floor

[PBado]

I have removed tiles from my shower floor by scraping then grinding away old adhesive. I am still left with a smoothie surface, with no loose adhesive but grind as I may cannot remove this vague tile pattern which seems to follow original grout lines.  Am I safe to continue on to waterproofing or should I continue grinding. It does not appear to be adhesive that is still there.  Thankyou for your advice.

[JacobZ]

Hi @PBado,

Welcome to the Bunnings Workshop community, it is fantastic to have you with us.

Those faint outlines are usually staining, from slight variations in the substrate surface and how they are exposed to water over time.  

Waterproofing membranes are designed to go over sound substrates and will bridge minor surface variations like that without issue. If the surface is solid, smooth, and free of loose material, you do not need to keep grinding just to remove the ghost pattern. 

Let me know if you have any further questions.

Jacob