I've found that making a solution of 80% White Vinegar and 20% Dawn detergent works well. I keep a gallon batch handy. When needed I heat 1 cup in the microwave to 150-160 degrees (F) and transfer it into a 1 quart spray bottle, that has been insulated by wrapping it with a hand towel, secured with two large rubber bands. Before using the heated Vinegar/Dawn solution, I first spray the room temperature solution onto the glass block walls of the shower, and scrub gently with a green scotchbrite sponge. I leave the lathered glass block sit while I heat the cup full. Then, I hose down the glass with scalding hot water. Next, I spray a liberal coating of the hot solution (top to bottom) & let it sit for 5-10 minutes, before rinsing it off with scalding water. The detergent helps the vinegar-foam cling better to the glass surface. It also works on fixtures, stone and ceramic surfaces. BONUS! It works wonders on windshields after a winter of salt and sanded roads too!