How to get rid of mould?

Oh warm and fertile Spring, new growth bursting out all around.

Which in our flat means mouldy ceilings.

I gaze up at it as I lie in bed each morning. No more peaceful lie-ins, instead I watch it's spidery progress, and plot its demise.

Years past have seen me don the rubber gloves and head into battle with bleach. That brings instant gratification, but no long-term satisfaction. A few weeks later I'll wake up, look up, and there it is again.

So this year is going to be different. First step: off to the internet for a bit of research. Where I find that the mould has been laughing at me, in between burps. Yes, bleach takes away the colour, but behind its cloak of invisibility the mould lies impervious. Worse, it's able to digest the bleach, and so when it gets its colour back it's stronger than ever.

The truth about mould's appetite for bleach comes courtesy of Mycologia's Mistress of Mould, Dr Kemp [1]. She says to put down the bleach and turn to ... vinegar! And not just any vinegar. Apparently the supermarket cheapy won't be any use: "only white fermented vinegar seems to work, as synthetic acetic acid does not appear to be effective". Who'd have guessed?

So, last week I donned the gloves again, but this time set to with cloth and a bottle of the finest white wine vinegar. Initial results were mixed. There's no post-bleach-fumes sore throat, which is a major plus. But on the other hand the house smells like a chip shop. Never mind, the authentic chippy aroma is a small price to pay if the mould stays away.

One week later and there's mould again, but it's mostly in places that didn't get a wipe last week. So, they've been given the vinegar rub-down too. We'll know in a few weeks whether victory is mine.

Readers, any other solutions to suggest?


[1] - Mycologia Pty Ltd's 'Myths about Mould' page



sunlight, a ceiling fan and a strong dehumidifier .....

our house in Spain got so bad at one point we had a mushroom growing out of one of the bedroom walls!

I believe that a mixture with bicarbonate of soda also can work ...

Some moulds are really bad for allergies etc ...

catch it early

I find surface mould can be dealt with quite effectively with a dry cloth. But it's a short term solution.

I've got anti-fungal paint (dulux pentalite) on the walls which worked well for about two years before losing the battle of attrition being waged at the microscopic level.

Mould spray - other than the issues outlined above - seems to cause annoying smudging if you're not careful and I fnd that when using it you need a sponge that is absolutely spotless each time it goes on the wall (which means a good couple of minutes cleaning before each wipe - great way to waste time).

I've got an apartment that rarely sees much breeze, even when its windy, so dealing with this stuff can be a pain - would love to know if the vinegar trick has worked...

re: mould


we haven't got mushrooms growing yet, so I'll look on the bright side! Our younger daughter has skin allergies, which is an added incentive to keep the mould at bay.

A de-humidifier with the windows closed will be a last resort, as I like to have the windows open as much as possible. Unfortunately sunshine (the flat faces north) and ceiling fans (low ceilings!!!) aren't an option.

I can't find any mention of Sodium bicarbonate, but there are some web pages that say sodium carbonate will kill it. That could be another line of attack.


We've used the dulux pentalite too, which definitely helps, but only for a year or two as you say.

The vinegar results haven't been great. I wrote the above about a week ago, just before the last few days warm and humid weather. Now the mould is back - it just looked as if I'd helpfully spread it around with my wiping!

I wonder if I need a stronger vinegar concentration (ie more acidic), and have just written to Dr Kemp:

If we want to kill mould at home, what type of vinegar should we use?

I've read your 'myths about mould' page. I bought white wine vinegar at the supermarket and mixed 4 parts vinegar to one part water, thinking that would give the '80% vinegar solution' you describe.

But a week after wiping, the mould is back and worse - it's now in broad streaks where I wiped it.

I think the vinegar was for salad use, so about 5-6% concentration, or 4% after I added water. Should I be using a stronger concentration?

I'll let you know if I get a reply, and if I make any progress.

Regards, MrB

A question: if you're

A question: if you're renting, are you within your rights to ask your landlord to deal with the mould?

Mould in rented accomodation

Hmm, good question. Ideally it would be spelled out clearly in your rental agreement, but it probably isn't, so...

If it's just the type of mould I've shown above, I'd say that's the tenant's responsibility to clear up. It's just a fact of life that Hong Kong's climate is mould's idea of heaven.

But, if the mould is caused by water leakage due to damage to some part of the flat's permanent structure (leaking pipes / cracked walls / etc), then it's the landlord's duty to fix that.

It will also depend on what type of landlord you have. When I rented we generally saw them once when we signed at the start of the lease, and once when we collected the deposit a couple of years later. But another time I was surprised to hear friends phoning their landlord and telling him to come over, because a light bulb had broken and needed replacing!

If you're thinking of any re-painting work to cover up old mould / slow down the growth of new mould, you'll need to check with the landlord if it's ok, and there's a good chance to get them to pay for materials at least. You're in the strongest position to arrange this when you're about to sign a new lease / renewal, and make it a condition of signing.

Please let us know what happens in your case.

Readers, any other advice to add ?

Regards, MrB

We've lived in the same

We've lived in the same apartment for over seven years now, have never repainted and, knock on wood, mould has been pretty manageable. The main thing we do is regular use of a dehumidifier. To my mind, at its root mould is a humidity problem. So in a climate like this if you're always leaving your windows open and never running a dehumidifier, you're bound to be fighting a neverending battle. This doesn't mean you have to seal yourself in all the time, but just now and again with a strong dehumidifier running. Though in the particularly bad times like now or during typhoon season, we'll run the dehumidifier every night. It makes a big difference, as you'd be amazed how much mould-inducing moisture is in your flat.

Moldy Monday?

MrB, your article is well-timed. These past few days have been cold, so there's not a current problem with dampness and condensation at Chez Tall, but man, did we have a mess last week in those several warm, humid days preceding the latest cold snap. We had one particularly bad evening when it seemed every surface in our entire flat -- floors, walls, cupboards, toaster -- was covered in a sickening sheen of condensation. Like jabalong, we have no recourse other than to close the windows and run our two dehumidifiers non-stop. It makes the air stuffy, but at least we don't feel like we're sleeping on sheets that have come straight out of the washing machine.

Now, the biggest problems for condensation in HK flats occur in February/March, typically when the wind shifts to the southeast, bringing up warm and very humid air. The problem is worse immediately after a cold snap that has cooled down all the surfaces in your flat, thereby preparing them perfectly for drawing moisture out of the air as condensation. It's pretty dang cold right now (for HK, at least), and the forecast just released by the HKO has winds shifting to the east by Monday, and around to the SE on Tuesday, with rising temperatures and high humidity . . . sounds like the perfect formula for some world-class condensation.

Your spores are going to be happy, I'm afraid.

Mould removal

It is definitely that time of year again - mouldy walls, mouldy ceiling and (paranoia setting in now!) mouldy clothes...

After a few seasons of trying bleach or vinegar, we have been running dehumidifiers regularly this winter and I also tried a different method of removing the mould from the walls and ceiling.

Testing a diluted bleach spray, applying full strength bleach using a cloth to dab it on the dark spots and a mixture of bleach and detergent, diluted in water and applied with a quality sponge, the mould survived the spray and also the direct application of bleach.

The areas wiped clean using the bleach/detergent mixture are still spotless after one month, (plus my arms and shoulders only took a few days to recover from the hard work...) Our apartment's paint is water based and the mould along with a minute amount of paint is removed by the sponge.

I used Tide coldwater liquid detergent and added 1 cup of detergent and 1 cup of bleach to approximately 4 litres of water.  Test it on an inconspicuous area first!

Good luck!

MrB vs. mould: Round 2

Mr Tall, as you predicted, my spores are downright ecstatic. No apparent benefits from the vinegar, so time to try something different.

Last week at the family CNY dinner, I asked for their collective wisdom on zapping mould. Oldest sister-in-law swears by 'luk soei' (literally 'green water'), and sent me home with a bottle. So that's what I'm trying now.

It was decanted into a clear plastic bottle, so I'm not sure exactly what brand it was. It smells a bit like Dettol (a disinfectant), and foams as though there's some detergent in it too. So hopefully it will work like the Tide & Bleach combo mentioned above.

After wiping the ceiling with it today, the bad news is that it irritates the throat (though not as badly as bleach), and doesn't have the whitening effect of bleach or vinegar. If it keeps the mould away for a few months, I'll live with that.

I'm still hoping to avoid the dehumidifier route, but maybe we'll have to give in at some point.

weather last few days

don't know what it's like where you guys live but the last two days have been really humid and the warm air is condensing on all surfaces like crazy. This is the worst I have seen it since I moved here in 2006. Guess what? My newly re-painted dulux pentalite wall is barely holding up. I need some of that "luk soei" - is that the actual name and can I buy it at the local shop?

luk soei

Phil, I've got a big bottle here you can have for free!

We gave the ceiling a thorough wipe with the stuff on Wednesday. The next morning mould had bloomed all over the wiped area. Plus I had a sore throat from the stuff.

Mould:2, MrB:0.


Okay, I realize we don't have the "fresh air" (though we do air the house out), but we have 4 dehumidifiers in our apartment (1100 sq/ft) and they run 24/7 (actually, our place really doesn't have good circulation, so it doesn't matter if we leave windows open or not--honestly).  The only place we have mold is the ceiling of one bathroom.  We've lived here 5 1/2 years and have never had a problem with mold.  Since two of us are allergic to it (along with one of us having asthma that flares up from allergies), we are very strict on the dehumidifiers.  Plus the several thousand books in the apartment--we just can't have mold and mildew in them because of the allergies.

I just don't see any other way in this time when it gets so humid and wet.  Plus, it avoids the slimy floors and damp bedclothes.

Hope you can find the solution to getting rid of the mold, however . . . .

Oldest sister-in-law swears by 'luk soei'

After having a bit of a chuckle (sorry, couldn't help it), I've decided to give it a miss. I am guessing your next encounter with the sister-in-law will be an amusing one.

She'll be recommending a bottle of "yellow" water next ;-)

mouldy ceilings


I like to keep doors and windows open too and have found that strategically placed air fans keeps the air moving around.  After treating with vinegar and letting it dry, I then wash the area with floor cleaner - blue/green or purple [I believe in invisible mould], spray with Dettol antiseptic spray and let it dry again.  So far so good.

Now, could you please let me have a remedy for ants? The little critters are just starting to investigate the kitchen again. I hadn't seen them for 6 months so thought they'd emigrated to the house next door.  Trust me, there isn't a single food item which isn't bagged and tagged to prevent spillage etc.



Wasn't there a movie about that?

Several anti-mould recipes I've seen mention Borax. It's also a common anti-ant remedy (eg this one).

I've tried the local chemists, but no luck. I've heard it's sometimes available in the Gateway store in Sheung Wan. I'll take a look next time I'm there.

If anyone knows where else to buy it, please let me know.

I'm also looking for strong (10% or more) vinegar, and strong (10% or more) Hydrogen Peroxide. Any ideas where to buy?

Yes, I've developed an obsession...

re: borax

Hi!  This may sound weird but I had heard that borax was used in Chinese cooking as a texturing agent.  Like for some deep-fried dimsum items, a tiny amount in the batch would make it crispier.  So perhaps it could be found at a food store?  It's banned here in the States for food use and it can be an irritant (or worse) depending on the amount of exposure and who's being exposed to it (according to Wikipedia).  In Cantonese, it is called "pahng sah fun".  (That's my romanization and I don't know the characters.)

What you might also try is to make an ant repellant by crushing dried spearmint leaves and scattering them around places where ants might get in.  It would seem safer as long as you're not allergic to it.


Wow - seems like a wonderful secret ingredient if not a little middle ages.  Fingers crossed it will work. I tried spraying with a commercial ant spray and believe I have eroded 1/3 of my lung cells as well as paralysing the little grey ones in the process.

mould killer

oil of cloves kills mould spores.  sprinkle it on a cloth and wipe it over the mould - what doesn't come off immediately should die off over the next few weeks - can add oil of cloves to a water spray botle and use that to wipe surfaces after cleaning.  upsides are it isn't as poisonous as borax and you get the smell of christmas all year round!

Oil of Cloves

Is it expensive and where can I buy it?

Re: oil of Cloves

Hi Phil,

It sounds like an essence oil.  If indeed it is and if you buy it at those aroma-theraphy stores it would very likely be expensive.  However as Cloves is also a common spice, I guess it should be safe to ask of local spice stores (or Indian supply stores) carry anything like that if you happen passing by one of them.

Cloves = 丁香  (pronounced as Ding Heung in Cantonese)  You'd probably what is oil in Chinese.  The oil did not come from the spice itself, but from the plant.   So ask if they have Ding Heung Yau in local spice stores or asking if they have Oil of Cloves in Indian Stores around.  Even if they don't have it they might give you some pointers.

Oil of Cloves has some medical use so maybe some local/community medicine stores might have something with it as part of the ingridients, however I am uncertain if those are suitable for fighting fungus.

Talking about fungus some would use diluted Teatree Oil to treat athelete foot.  I wonder if Teatree oil could be used similarly.  But it is expensive.

My 2 cents,


ps  When I googled for oil of cloves in Chinese I found some entries in fishing forums saying mixing oil of cloves with earthworms could usually yield a certain percentage more then using plain earthworm.  I have not heard of any odd-ball things like that ever.  But since you are into water sports, maybe you could ask about your water activity friends and see if they have heard of anything like that.  If so, they might as enlighten you a bit.

Borax beats mould

After false alarms with vinegar and the infamous "green liquid" (and also 'rubbing alcohol', which didn't work either), the borax has turned out to be a winner. Batpor also reports it solved her ant problem:

I forgot to mention that last week [or maybe the week before that] when we had a lot of rain, I had a sudden influx of ants in the kitchen.Anyway - mixed up some borax with peanut butter - yes we have to make these sacrifices - and it worked wonderfully. The next day, you'd have been hard pushed to find an ant on the premises. We used the tops off plastic sauce dishes and we've left a couple in the hot spots but so far its been brilliant!

The magic mixture I've been using against mould is Borax in Hydrogen Peroxide. Borax is available in Gateway. 6% Hydrogen Peroxide is available in any chemist. It's not a very scientific mix - I pour one or more bottles of the peroxide into a bowl, depending on the area I need to cover. Then I add a spoonful of Borax and stir 'til it dissolves. Repeat until there's some still showing, ie no more Borax will dissolve.

Then I use a couple of gloves that look like a sort of soft, de-boned hedgehogs. In pink. It also helps to get into a wax-on, wax-off frame of mind.

With dry hedgehog, wipe off the mould. Then with a second hedgehog glove that's been soaked in the Borax+Peroxide mixture and squeezed so it's damp but not dripping, wipe over the surface.

Not great for dark surfaces, as when it dries there's a thin film of Borax powder showing. But seems good for walls and ceilings - several weeks after wiping a troublesome ceiling the mould has stayed away, apart from a couple of tiny patches I probably missed on the first wipe.

Some websites note the toxicity of Borax, eg, or don't think it's likely to cause problems in the way I'm using it, but that's something you should judge for yourself.

If anyone else tries it, I'll be interested to hear how it goes.

And Phil please let us know how well the oil of cloves works if you try that.

Regards, MrB

i do 1 thing to keep mould away

I moved in this flat 3 years ago and suffered strong mold smell in the bedroom and visible black mold all over the bathroom and parts of the kitchen.

My clothes, cowboy boots, training belt etc all got ruined by the stinking stuff.

One day I tried "Dettol Mold and Mildew Remover" on the mold ridden kitchen blinds. It said on the bottle leave for at least 5 minutes so i left it 20 minutes and it did nothing. I decided to throw out the blinds in the morning and went to bed. In the morning I stood there open mouthed because the blinds looked like new. I realized I had left the Dettol stuff on overnight.

I was on to something - so I sprayed all the mould on the bathroom walls and tiles leaving it on. Within about 4 hours the bathroom was clear and mold did not show again for months and the Dettol dried clear too.

So whenever mould seems to be returning anywhere i just spray and leave it on just wiping any runs or drips with kitchen paper roll.

Major Notes ....

a) if the surface you spray is not colorfast (ie clothes) THEY WILL BE STRIPPED OF THEIR COLOR so wear old clothes or go naked :-)
My black bathroom blinds went pink too so watch out - though iv never had a problem leaving it on painted walls or colorfast blinds

b) the smell is like bleach and is very strong for about 3+ hours so vent the place and clear off out for the afternoon

c) 5 minutes on a colorfast surface is usually nowhere near enough so i just leave the spray on permanent as the smell goes away after a few hours and mold doesnt seem to like growing back on the sprayed areas

I spray any areas mold seems to be returning (colorfast) for 2 years now and if its dead within hours :-)

4) Mould smelling clothes might need throwing out but try adding a cup of white vinegar to a normal clothes detergent wash and hope for the best.

5) while you have mold keep all your clothes in air tight plastic bags

6) if the mold is behind wallpaper strip that paper off and spray the walls with "Dettol Mold and Mildew Remover" leave a few hours, then put on new paper with mold resistant paste

all the best

HK Mould

Eucalyptus oil

Available at industrial chemical shops in Hong Kong & Kowloon

Wipe the area about once every 6 months, on some surfaces it will last a year. The smell dissipates after a couple of days.

Previous suggestions mention mixing bleach with detergent. This is very dangerous as a chemical reaction then produces a poisonous gas.


If you don’t want to use chemicals (bleach, borax, detergent), and don’t like the smell of vinegar or oil of cloves (Chinese medicine, eucalyptus, etc), another solution is to use lemon juice. It won’t keep the mould away permanently, but I’ve had success for a good few months.

Great website btw.

Re: "Dettol Mold and Mildew Remover"

Hi Riff, can you please tell me where to buy the "Dettol Mold and Mildew Remover" in Hong Kong? I've looked everywhere but can't find it. I saw many other Dettol anti-bacterial and cleaning products, but no mold-specific remover.

Thanks a lot,


try Japan Home Store

I bought it from there previously. Didn't have as much success as Riff though :-(

Hydrogen Peroxide 10% or

Hydrogen Peroxide 10% or more, i've seen it in shop with hairdressing goods (such as dyes, shampoons and all those styling gels). However, such Hydrogen Peroxide will be cream-like. Hope you find it in HK.

Best Regards,

Ms Be

Stay away mould

Not so much how to get rid of mould but rather keeping it away.

I currently use good old BBQ charcoal. My storeroom is smelly and likely to have mould growth but I've stuck a bucket of charcoal in there to great effect. It's acting as a dehumidifier.

There's also calcium chloride, but I haven't found a source for that in HK.