Let’s not pretend here. The drawback to using real soap in the bathroom is that you have to face the reality of scum. Soap scum, to be exact. It’s gonna happen. So let’s face it head on. (As a sidenote, if you don’t have scum in your sinks or tubs, you might want to check and see if your body cleaning products are actually detergents.)
First off, what it is. Soap scum is a bit of a misnomer because there is not actually soap left on the sink or tub that just didn’t get rinsed away. Instead, it is a salt produced from a reaction between the soap and minerals in the water. This is why, if you have hard water (i.e. more minerals), you have more soap scum. If you have soft water, you won’t have as much.
Be that as it may, let’s get rid of it. I have two preferred ways of getting rid of soap scum.
The Dissolving Method
The first is to dissolve it with vinegar. Dilute one cup (240 mL) of vinegar in a quart (1 L) of water and spray it on the scummy surfaces. Let it sit for about 5 minutes (not long enough for it to dry), and then rinse it away with very hot water. If your scum is really thick, you may have to do this again or use a stronger concentration of vinegar. (As I’ve said before, take care with using vinegar on soft stones like marble. It will etch.)
The Scouring Method
The second method uses brute force. This involves scouring the scum off with baking soda sprayed with an All-Purpose Cleaning Spray made with Castile Soap. (Wait! Spraying soap scum with soap? I know it sounds like this will compound the problem. I’ll get to that.) To do this, I spray the sink or tub with my Castile Soap All-Purpose Spray. (The All-Purpose Spray made with Sal Suds works equally well.) Then, I sprinkle a cupful (240 mL) of baking soda liberally on the sink or tub. With a washcloth, scrub all the surfaces and rinse with very hot water.
The Soft Scrub Method (Added 9/30/2019)
This method is perhaps the most fun, but it takes a little longer in the preparation. A GIY (Green-It-Yourself) Soft Scrub, from Karen Logan’s book, Clean House, Clean Planet, clings to vertical surfaces, such as tub or shower walls, and provides the soft abrasion to clean off any soap scum, or whatever else might be there. It’s made of Dr. Bronner’s Liquid Castile, Baking Soda, white vinegar, and water. Check out the how-to here: GIY Soft Scrub with Dr. Bronner’s.
Lastly, after whichever method, dry the surfaces.
Here is the trick to preventing future soap scum, and why the second method works. If you dry the water off the surfaces, there are no dissolved salts sitting there that would later cling to the surfaces when the water evaporates. For large, flat areas, such as shower stalls, especially with glass, use a squeegee. I keep a squeegee in my shower stall and do this after every shower. Sounds like a pain, but it greatly cuts down on my work in the long-run.
I generally use the dissolving or soft scrub method. The soap in each of these also eliminates germs that may be residing on the surfaces . Vinegar does this to an extent, but the soap does it better. And I like scrubbing. It’s cathartic.