My wife and I recently bought a new home, and the shower in the master bath is a relatively tight stall shower. In order to fit a human body in there and still have access to all of the necessary items needed in a shower, we wanted to install corner-shaped bins into one of the corners of the shower, but without drilling holes in the tile. Suction cups to the rescue!
However, we discovered that our tile is not smooth enough to hold a suction cup for more than a few minutes, and our shelves were falling down.
I considered glue, double-sided tape, and sticking smooth-surfaced items (ie. cut glass or plastic) to the walls so the suction cups would hold.
But in the end, I hit on a simple solution that's been holding strong now for over a month.
Step 1: Try to Stick the Suction Cup
The first step is, naturally, try to stick the suction cup right to the tile. If you can stick it and it doesn't pop right off when you pull on it, congratulations, you don't need this instructable.
On my tile, the suction cup pops right off with little or no force.
Step 2: Locate a Spot and Clean the Tile
I used isopropyl alcohol to ensure no leftover reside was left on the tile. Make sure this is safe for your tile before using it.
Step 3: Select a Tape
Here I'm using standard-issue packing tape; it's about as wide as this suction cup.
Note: unfortunately you can't overlap pieces of tape for larger suction cups. You will need to get bigger tape, or smaller suction cups... the seam in the overlapping pieces of tape (or tha gap if you try to put them side-by-side) allows air in and you won't get good suction.
Step 4: Cut the Tape and Stick It
Use your fingernails to rub the tape into the wall - you want to eliminate air pockets and force the adhesive into all the nooks and crannies of the textured surface so it will hold up under the vacuum pressure from the suction cup.
Step 5: Stick the Suction Cup
Note: over time, the suction from the suction cup may loosen the tape. If that happens, your suction cup should still hold, but you might want to just re-rub the adhesive back into the tile.
That's it! Packing tape is clear, so you'll never see it, and it's safe to wash as long as you've sealed down the edges well with your fingernail. It comes right off when you no longer need it, and it will make you muffins for breakfast.
OK, maybe not. Just checking to see if you're still reading. ;-)