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Moldy Shower Caulk… Fixed!

By In Moldy Caulk On April 19, 2011

Dirty bathrooms are a huge turnoff for home buyers.  Mold is another huge turnoff.  Combine the two and the ‘yuck’ factor multiplies.  I think everyone has seen moldy bathroom caulk before, and if you’ve tried cleaning this stuff, you know it’s impossible.

Moldy caulk in shower Moldy caulk in shower close-up

I recently moved into a home with some nasty looking caulk in the shower; that’s my shower pictured above.  I figured I would need to remove all of the moldy caulking and re-caulk my shower walls to get them looking good again, but after doing some online research, I found a cleaning method that worked surprisingly well and wasn’t much work.  Don’t worry, I’m not going to turn this into a Martha Stewart blog… but I was so happy with the results that I had to share the process.

Gather supplies. I grabbed a small mixing bowl, a jug of bleach, a box of baking soda, a disposable paint brush, a roll of plastic wrap, and a spray bottle.  The plastic wrap (orange handle, green plastic) shown in the photo below is the stuff you use to wrap things together, but you can also use the same plastic wrap you keep in your kitchen.  Oh, and one other thing – while it’s not required for the project, I strongly suggest wearing a respirator.  Those bleach fumes are bad news.  Also, wear old clothes that you wouldn’t mind spilling bleach on.  It might happen.

Cleaning Supplies

Mix up your cleaning solution. The cleaning solution consists of a bleach and baking soda paste.  You make it by mixing bleach and baking soda in a bowl until it’s about the consistency of pancake batter.  The baking soda doesn’t do any cleaning; it’s just a cheap powder that will help make the bleach pasty.  Don’t skimp on the cleaning solution here – go ahead and make way more than you think you’ll need.  Bleach and baking soda are both inexpensive.

Disintegrated paint brush bristlesApply the cleaning solution to the moldy caulk. Use your disposable paint brush to apply the bleach paste on to the moldy caulk.  Again, don’t skimp here; it’s cheap, so cake it on.  I suggest you try to work somewhat quickly though.  The bleach might disintegrate the bristles on your disposable paint brush, so you might not have all day.

Cover the cleaning solution with plastic and wait. Covering the cleaning solution with plastic will help to keep the bleach from drying out.  Now you wait.  If you have a white porcelain kitchen sink or white porcelain whatever-else, spread the extra cleaning paste on it.  You can just let the paste sit for about 10 minutes, and then your sink will look brand new when you rinse the bleach off.  No scrubbing required.

Check on it. After the bleach has been sitting for several hours, it will probably have dried out, despite the plastic covering.  At this point, if the caulking looks as good as new, great!  You’re done.  If you still have moldy caulk, put some bleach in a spray bottle and wet the walls down right above the plastic wrap.  The bleach will run down underneath the plastic and re-saturate the paste.  You can do this as many times as it takes, but even with my super-nasty caulk, I only needed to re-apply the bleach one time.

Now clean up.  At this point, your caulk should look brand new and bleachy fresh, or at least pretty close to it.  Now you can clean up the mess.  Water works just fine.  Click on the before and after photos below for a larger version to see how well this worked.  If I were a better photographer, all of the whites would have looked the same, but oh well… I think you get the point.

Moldy caulk before and after

Moldy caulk before and after closeup

I was amazed that this worked so well.  The entire project probably involved about 20 minutes of work, and required no elbow grease whatsoever.

And now, a word of caution:  do this project at your own risk.  Bleach is powerful stuff.  Read the warning label on the bleach.  It says to use in a well-ventilated area, don’t let it touch your skin, don’t breath the vapors, etc.  Bleach can also cause pits in metal.  I used it on the metal trim ring for my shower faucet and no pitting occured, but other people might not be so lucky.  Also, I’m not kidding about wearing a respirator.

Reuben Saltzman, Structure Tech Home Inspections




About the Author


Reuben is a second generation home inspector with a passion for his work. He grew up remodeling homes and learning about carpentry since he was old enough to hold a hammer. Reuben has worked for Structure Tech since it was purchased by Neil in 1997, and is now co-owner and President of the company.


  • matt 3 YEARS AGO

    Can you just wash everything down the drain, or do you have to scrape it off and dispose of it in the garbage? Is all the baking soda safe for drains? I think I will try this on my clear silicone sealant this week...

  • Barbara 3 YEARS AGO

    I just tried this with amazing results! I had run out of cleaning options and sure didn't want to re-caulk. Did a Google search and found your website. It was easy and quick. I will do this every couple of months to keep the mold away. Thanks!

  • rob 3 YEARS AGO

    thank you

  • rob 3 YEARS AGO

    we have cleaned our grout lines as described in your blog but my question is that should we reseal the grout since we have scrubbed it and it may not be sealed anymore

    • Reuben Saltzman 3 YEARS AGO

      @rob - this was about cleaning moldy caulk, not grout. If you scrubbed your grout, I'm sure it couldn't hurt to reseal it.


    Son's new apartment has caulk, not grout around the shower tiles. It's black to say the least and gross. Will try this solution this week, but any other tips when doing way more than just the caulk line between the wall and the tub?

    • Reuben Saltzman 3 YEARS AGO

      @Susan - caulk around the shower tiles? Tear the whole thing out and start over. Short of doing that, try the same approach as above. Let it sit wet for a long time. Re-wet as needed.

  • Janet O 3 YEARS AGO

    I just did this at my son's house while they were out of town on vacation. I saw on his "honey do" list to re-caulk the shower and it was the only item left on the list. So, while they were gone, I thought I would give it it a try. Absolutely amazing! It is as white as toothpaste. They will think I re-caulked his shower. I walked to several neighbors and showed them my before and after pictures and most of them gasped! I did leave it on for a day and a half as they were gone as I thought "more is better." THANKS FOR THE GREAT CLEANING TIP OF THE YEAR!!!!

  • Nora 3 YEARS AGO

    This worked great. Thanks so much for posting this. I pinned my results on pinterest: http://www.pinterest.com/pin/423338433694090185/

  • Christina 3 YEARS AGO

    I want to go to my new apartment and try this right now! Its so nasty. Do you think this will also work on the grout between the tiles?

    • Reuben Saltzman 3 YEARS AGO

      @Christina - I've heard that diluted vinegar is the way to go. http://blog.homespothq.com/2013/08/how-to-clean-bathroom-tile-grout/

  • Nicole Polley 3 YEARS AGO

    Will this baking soda and bleach solution work on moldy rubber gasket around patio door? If not, any other suggestions. Tks Nicole


    Simply amazing. I scrubbed it so many times I figured there was no way except to remove the caulk. Took a shot at this suggestion and it worked like a charm, it looks brand new. Keep up the good work

  • Goody 3 YEARS AGO

    We have a glass block window smack dab in the middle of the shower - so there's no ventilation in the bathroom other than the fan. Since we bought the house, we've had a terrible time w/mold on the trim around that window (only where the water hits). I saw this posting & thought I'd give it a try . . . 2 hrs and it looks amazing!!!! I couldn't believe it! Thanks so much -

  • Shannon 3 YEARS AGO

    Worked like a charm! Thank you so much!!!! Saved me so much time and work. Just can't thank you enough :)

  • R. Reiton 3 YEARS AGO

    THANK YOU. You just saved me hours of work that I thought I had to do but didn't! It worked beautifully! My grout wasn't nearly as bad as yours, but I still did two applications; there's some pitting in the caulk where I had a few stubborn spots, but the second time got it all!

  • Jennifer 3 YEARS AGO

    Sorry- I should have clarified that we only started with a few spots of mildew. We ended up with the same number of spots...

    • Reuben Saltzman 3 YEARS AGO

      @Jennifer - maybe the mold is behind the caulk? In that case, saturating the wall with a spray bottle would help the bleach soak in to the grout and get behind the caulk as well.

  • Jennifer 3 YEARS AGO

    OK so I followed these instructions except for the spray bottle but it made almost no difference. I left it on for more than 5 hours- a very thick paste and we only had a few spots of mold/mildew. What do you think went wrong? I really gooped it on.

  • George 3 YEARS AGO

    Sounds like a great idea. How much bleach to be effective?

  • George 3 YEARS AGO

    Sound like a great idea. Roughly what ratio of bleach and soda to get pancake batter stage ? .

    • Reuben Saltzman 3 YEARS AGO

      I've never actually measured it out; just try adding a little at a time. You'll figure it out quite quickly.

  • Connie 3 YEARS AGO

    What happened if the mold and mildew is under the caulk. I'm I going to have to remove the caulk? Using your suggestion now, but does not look like its going to penetrate the mold under caulk

  • Alyson 3 YEARS AGO

    Our shower looked grubby and nasty as alot of the sealant and some of the grouting had gone black and discoloured - i have tried all sorts of 'off the shelf' products, none of which had made any difference, and stumbled on your website. I thought it worth a try but wasn't sure that such a simple idea would work - how wrong was i - easy to do and what fantastic results! Our shower looks like new for such a small cost and not alot of effort. Thank you so much! :)

  • Chewy 4 YEARS AGO

    Thank U ! Worked like a charm! Nothing else worked.

  • Robert 4 YEARS AGO

    This was a great way to get my shower looking like new. Now I don't have to strip and r-caulk my shower! Thank you for your help! I will pass this helpful tip along to anyone who tells me that that they have a black mold problem in the bathroom.



  • Joan 4 YEARS AGO

    As I painfully started removing my caulking I thought THERE HAS TO BE A BETTER WAY!!! Thank you so much for posting this. It works like magic!!!!!

  • Cassie 4 YEARS AGO

    Well, my caulk had broken the seal and the mold had formed between the caulk and the shower stall. Spent a lot of time removing the old caulk and cleaning the walls really good. Just applied a new bead of caulk last night. I got up this morning and some of the brown gunk that had been in the crack (that I cleaned really well) leeched up into my caulk. So now I have a pretty bead of caulk around 3/4's of my shower and brown spotted caulk on the rest. Do I take it up again? Can I apply another bead on top?

  • Erica ! 4 YEARS AGO


  • Erica ! 4 YEARS AGO


  • Chup 4 YEARS AGO

    Did u diluted bleach or used as it is? Thanks in advance

  • Nicole 4 YEARS AGO

    This turned out amazing. I felt depressed every time I showered because the tub was so gross. We all slept downstairs last night because there were definitely decent bleach fumes. I am so proud of the results. Thank you!

  • Emily 4 YEARS AGO

    Hi! This idea sounds wonderful! I really would like to try it. I have been looking for a solution to the embarrassing 'black caulk.' I'm not sure it will work because my shower is not white. Do you think I can try in on an off-white shower/tub?

    • Reuben Saltzman 4 YEARS AGO

      Emily - I would think so. As they say, test on an inconspicuous area first.


    Do you know if I could use this method for cleaning caulking around cultured marble shower walls? thank you!

    • Reuben Saltzman 4 YEARS AGO

      Elaine - no, I've never tried this on cultured marble.

  • Juan 4 YEARS AGO

    I read this post and thought, it kind of made sense, but sounded too good to be true. I decided to give it a go expecting it to fail. I was blown away! If my wife did not witness it for herself she would have thought I took the caulk off and applied new caulk. It came out BRIGHT white. I have been telling everyone about this amazing solution. I wish you inspected homes in Philadelphia. I would recommend you to anyone. Thanks.

  • Savannahman 4 YEARS AGO

    How about Cultured Marble? Will this method work w/o damaging?

  • CVinny 4 YEARS AGO

    Thanks for the tip! I initially tried this with baking soda. It mixed well, but didn't give quite the pastey consistency to go up the wall. I did, however used Ajax as a substitute and when applied, appeared to have turned white instantly! At any rate, thank you so much for the tip as I will never be afraid to tackle a moldy shower again! :-)


    Worked great- thanks for the tip!

  • Patty 4 YEARS AGO

    OMG. This is amazing. A few years ago I actually spent days and days removing and replacing caulking only to have mildew return some months later and I clean my shower consistantly. I finally gave up and figured it is what it is. I found your web site today and thought what the heck. I have all the stuff, whats one more internet remedy try and fail right? All I can say is WOW. For the first time in years Im not embarassed of my shower. many thinks... Would this work on years old floor grout?

  • Amanda 4 YEARS AGO

    Is this safe to use while the kids r home? One is 3 years and one is 5 months....

    • Reuben Saltzman 4 YEARS AGO

      Amanda - I'm not qualified to answer that. I'm sure some people would tell you it's not safe to use bleach for anything, ever.

  • mrscastillo 4 YEARS AGO

    Thank you! thank you! It worked!! my bathroom is clean with this simple idea. Just two hours. I got crazy & brushed everywhere: sink, toilet bowl. tub. White & shiny.

  • Mel 4 YEARS AGO

    OMG thank you for posting this. I gave this a go myself and in some places it looks better than new. I need to go back and perfect my technique. I found that if i stuck the plastic first and then peeled just the top open i could really slather more "bleach paste" in there (sometimes mine would start sliding down the side of the tub before i could get the plastic on.) This was a life saver for me!

  • Gen 4 YEARS AGO

    Fantastic! Just did this today...left it on for about 2 hours, back to white again!

  • Kathy 4 YEARS AGO

    This post was a life saver! Moved into a house and the shower hadn't been cleaned for what seemed like years. Cleaned the soap scum with Magic Eraser and then followed your how-to on how to fix the moldy caulking. I never thought I would be able to get it clean but I was amazed at how it worked! So easy and cheap and the caulking looked bright white-no mold! Thank you thank you thank you!

  • Brittney 4 YEARS AGO

    Thank for this so much! I am excited to try this! Our house is about 30 years old and the people before us obviously never cleaned....the tub :/ So this is great! I have gotten the bathtub to look great but that darn caulking! Again Thank you SO much!


    Thanks, I am interested in trying this but does it matter if the caulking and tiles are not white? Will the bleach ruin the coloured caulking and/or the tiles?

    • Reuben Saltzman 4 YEARS AGO

      Heidi - good question. I've never tried this on anything that wasn't white. Try it in an inconspicuous area and let me know what you find out.

  • Carolyn Bishop 4 YEARS AGO

    Thanks for the tip! I thought I was going to have to re-caulk my shower after many failed cleaning attempts. This solution did the job, and I will recommend it to others.

  • Gwen 4 YEARS AGO

    Where can you buy a respirator? The hardware stores only carry dusk masks, which aren't enough.

    • Reuben Saltzman 4 YEARS AGO

      Gwen - any big box store such as Home Depot, Menards, or Lowes will have them. Any paint store will have them too.

  • Moly Keeler 4 YEARS AGO

    works great! I used a plastic knife to spread the goop around, it worked great!

  • Anne - I have another question, we live in an area where we get a lot of hard water deposit build up, and I'm always fighting the lime with vinegar b/c I don't like using Lime Away - it's so toxic. Will your clorox paste take care of 2 birds with one ston 4 YEARS AGO

    I have another question, we live in an area where we get a lot of hard water deposit build up, and I'm always fighting the lime with vinegar b/c I don't like using Lime Away - it's so toxic. Will your clorox paste take care of 2 birds with one stone (mold and lime)?

    • Reuben Saltzman 4 YEARS AGO

      I don't think the bleach will do anything to get rid of the hard water deposits. You're stuck using vinegar or Lime Away.

  • Anne 4 YEARS AGO

    Can't wait to try this at the bottom of my shower doors. Can you tell me how long this lasts?

    • Reuben Saltzman 4 YEARS AGO

      Anne - this lasted about 16 months. Mold is just starting to show up again at my shower caulk.

  • Shannon 4 YEARS AGO

    I just tried this trick this weekend and I didn't really expect it to work that well, but it did. I had some mild dark mold in the caulk in my shower. There were a couple of black spots and several more areas that were on their way to turning black. I followed the directions -- just mixed baking soda and bleach until I got a thick consistency -- spread it on the caulk with a paintbrush from the dollar store and covered it with plastic wrap. I let it sit for two hours and came back to check on it, and it had already done the job. All of the dark spots are white again. This is such a great trick! Thanks to the author for posting this. My sister was at my house when I wiped off the paste and she said she's going to try it in her bathrooms.

  • Kaysee 5 YEARS AGO

    I can't wait to try this! One question - did the plastic wrap generally stick to the walls by itself? Thank you for this!

    • Reuben Saltzman 5 YEARS AGO

      Kaysee - yes, the liquid basically held the plastic against the walls.

  • Miss T 5 YEARS AGO

    Will this also work on moldy silicone shower sealant between the wall&shower stall?

    • Reuben Saltzman 5 YEARS AGO

      Miss T - I've never tried it. Let me know how it works.


    So, I wanted to post, even though this article is a tad old by now. I honestly did NOT have my expectations set very high. Our grout and caulking was embarrassing. Just utterly disgusting. While we could have cleaned it more often, it's not ENTIRELY our fault (ok, it is, but....). We have a soft water system which removes all chemicals, including chlorine. After about 2-3 weeks, we notice the shower is incredibly dirty... In one way it's fortunate to say it's luckily NOT from soap scum, but rather mold and mildew starts forming as soon as a week after cleaning. Low and behold, I tried your idea, and only left it on for an hour and a good majority of it came clean. Sparkly white. I need to do another application, but it's certainly better than it was before! As someone else said, my paintbrush didn't dissolve either... Maybe it has to do with the type of paintbrush (I got mine at the dollar store, fully expecting them to dissolve).

  • Joe Hancaviz 6 YEARS AGO

    I just got done with mine. It looks a lot better, but it didn't remove all of it. Maybe I didn't get the proportions right - my paintbrush didn't dissolve. At least it's good enough that I think I can get away with scratching the recaulk job off my to-do list!

  • Jim Allhiser 6 YEARS AGO

    Reuben, Fantastic! I love your "how-to" blogs. I have been working on one (although not very hard) on how to clean windows. Surprisingly I have some caulking that could use some touch-up as well. Thanks!

    • Reuben Saltzman 6 YEARS AGO

      Jim - thanks! Are you doing one on how to clean the glass, or how to clean the entire window? If it's the whole window, I've got some great advice. The inside tracks on my 12 year old vinyl windows appear to have never been cleaned, and I've come up with a great way to clean them, if that's what you're writing about. Joe - ha! Maybe you just worked fast enough to not destroy your paint brush. At least it was a lot easier than re-caulking.