I recently put up a water proof membrane to prepare for tiling my bathtub walls. I mixed the thinset but it seemed soupy and very gritty. Did I do something wrong or is this how it is supposed to feel?? It did work the membrane is still up but i am getting ready to tile and I do not want to have the tiles falling off after a week. Please advise. Thank you all for any advise.

Sounds like you just mixed it too thin. When mixed correctly, it should be of a consistency like peanut butter and will stick to a wall.

Your too thin mixture will likely be OK now that it has cured as long as all the membrane is still in place without any sags or bubbles. One note: If your membrane is the orange Kerdi material, make sure that your thinset was an unmodified type. Modified thinset will not correctly bond any overlaps of fabric.

Thank You.