I have a fixed 7' glass panel that is 1/4" distance from a stone wall in a shower. The glass panel was designed to be fixed at only the top and bottom and to "float" off of the stone. However, moisture enters through the 1/4" wide x 7' void, damaging the adjacent gypsum board.

I would like to fill the vertical void with clear silicone, the entire 7' height.

Do I caulk from bottom to top, or top to bottom? How do I maintain the constant thickness of the caulk to align with the thickness of the glass panel (3/16")? Is there a temporary backing (i.e. painters tape or aluminum foil) that I should use to secure the caulk into place?

This seemed as if it would be an easy task, until I considered gravity's impact upon the caulk.

Many thanks.

Cover back side of opening with masking tape. Place masking tape on front edge of glass and on wall so that you get a nice straight edge of caulking. Caulk with clear silicone. Use only enough caulk to fill gap. The worst thing you can do when caulking is to use too much. Smooth with finger wet in acetone. After smoothing remove tape. Smooth back side with finger wet in acetone. As silicone begins to accumulate on finger, clean and rewet with acetone.