How to Clean Black Shower Mold Permanently

Posted by John on November 28th, 2012

Keeping with our bathroom theme… Unless you routinely scrub your tub or shower, you’re bound to get a good amount of black moldy build-up in those tough to clean areas. We’ve all seen it. Sorry if I’m starting to sounding like a commercial. It happens. It comes from years of trying to sell my ideas to Lisa. So, our master bathroom shower has seen some better days. Surprisingly, we actually DO clean it often enough that we shouldn’t have any issues with black staining mold or hard water stains, but nonetheless we do. Here’s how I was able to get our shower mold free and looking new.

How to Clean Black Shower Mold Permanently

First, I always start with a cleaning product that contains bleach. We typically use Tilex. The chemical odor can be pretty overwhelming, so whenever I use it, I try to keep the windows open to let some fresh air in and I wear a mask.  I aggressively work the cleaner into the problems areas with a stiff bristle brush.  If you still have some black mold after this step, then you’ll need to remove and replace the caulk.

Here’s what our shower looked like after the best cleaning it’s ever gotten.

shower mold

shower mold 2

black shower mold

Still pretty gross. To remove the moldy caulk, I used a box cutter with a sharp blade and a flat bladed box cutter, which is like a window scraper, to score it. Once all the caulk was scored, you can usually peel it out. Be sure to get all of the caulk out of the joints. Some of the more stubborn caulk may harden to the point that it’s like grout. The hardened stuff may need some more persuasion. I used a flat head screw driver. You do need to be careful that you don’t damage your tile or shower basin. Also, wear safety glasses. Proceed with caution and at your own risk.

Once all the moldy caulk was scraped out, it looked better.

caulk removed

after removing shower caulk

removing shower caulk 2

With all the caulk removed, it’s time to prep for the new caulk. Be sure to clean up the area where the caulk was previously. It will also need to be nice and dry in order for any caulk to adhere well.

Now, if this were a latex based painter’s caulk, I’d dive right in. The latex caulks are pretty easy to work with and are fairly forgiving. However, your shower and bathroom applications require a silicone based caulk. Silicone caulk is notoriously difficult. So, to make it easier on ourselves, we’re going to use some painter’s tape to mask off the area. I leave a good 1/4″ gap in the area where the caulk will be applied.

tape caulk joints

tape the joints

Once the tape is in place, we’re set.

Now, you can buy high quality silicone caulks that are specifically designed for a shower or bathroom application, as opposed to a window or door for example. The caulk we used for this repair guarantees several years free of mold. Hopefully, with normal cleanings, we won’t need to repeat this procedure.

Here’s a link to the caulk I’d recommend if you are considering this project.

The caulk can be applied in a thin bead and can then be smeared with your finger.

apply caulk

smear the caulk

While smearing, I try to get a seamless look. Pull your finger smoothly across the caulk line and don’t stop until you get to a corner. Once you’ve smoothed all the caulk, remove the tape. Very gently, re-smooth out the caulk lines again. You’re done. Let it dry according to the caulk manufacturer’s directions. You usually need to wait around 8 hours after you apply the caulk until you can shower.


clean white silicone caulk

fresh shower caulk silicone

Now, my assumption is the builder didn’t use a high quality caulk the first time around. We’re going to be more vigilant this time and hopefully can clean the shower with a less caustic cleaner, but I’m hoping I won’t need to repeat this for a long, long time. And if you do spot some small black mold spots in your caulk, don’t fret. Try letting the Tilex cleaner soak for a little while (few minutes) before you plan on re-doing it.

The hardest part of this whole process is removing the old caulk. Plan on this whole fix taking at least a couple of hours. It will be time well spent.

Anyone else dealing with some crappy caulk? I wrote an entire post about caulk and didn’t make one juvenile joke. #itskillingme’

This post contains one Amazon affiliate link, but feel free to purchase caulk wherever you’d like. :)

Posted in DIY Projects,Fixes,Plumbing. Tagged in ,, , , ,

  • We have the exact same problem, and in one of the corners as well! The rest of the caulk is completely fine. I was actually staring at it this morning and thinking we should do something about it. Thanks for the tutorial!

  • casadechristine

    Looks so much better!!

    • John_OHFScratch


  • I need to try this with our shower! But I think it's more hard grout than caulk, so I don't know if I actually can… :

    • John_OHFScratch

      Actually, when the caulk hardens, it feels and looks like grout.

  • I feel your pain, except in this shower (or as we call it, the shower-pod), the doors always look dingy regardless of how often we clean it. A year of being here, and we still haven't figured out the right formula. Hopefully soon!

    • John_OHFScratch

      Cleaning showers never seems easy for some reason. Our door is scummy. Sucks.

      • Sehlers

        Spray your shower door (I'm assuming it's a clear door) with W-D40 and wipe clean. I just cleaned mine and it works! My sister told me about it. It's not like brand new, and you many need to do it more than once, but it makes a big difference!

  • Looks soooo much better! Great job! 🙂

  • Bill Lockhart

    Someone suggested using RainX on the glass said it would keep hard water, soap scum off for about 6 months, and it’s certainly easy enough to use.