Any guests there by themselves for a few days? They could have spilled something on one slipcover, but laundered them all and replaced them while damp?

The heating and cooling split systems have a drying feature.

Could people have sat on them with wet or damp suits or cover-ups? The marks look kind of "bum-sized."

Is it possible that your cleaning service wiped the cushions or the slipcovers with a wet rag to clean them after you let the house the last time?

adding… if you bleach the white slips you can use them again. People have a very odd, almost knee jerk reaction to mold. Most types can be easily remediated.

Do you have a hygrometer? I’ve used one in the basement certain times of year to know when I need to turn on the dehumidifier.

Is it possible that you have mildew not mold? I’d wash the covers and pitch the cushion forms.

A product called Benefect that some professional mold remediators use is available on Amazon. It also works on mildew.

Haven't you lent or rented this house? I think the wet bathing suit suggestion might be the answer. Especially if not ALL of them are like that...only the ones someone sat on. Since it hasn't been like that for all the years you've lived there and is recent, that would be a reasonable explanation for why now and not before.

Sorry, busy playing a new card game.

Bbstx, maybe it is mildew, not sure I know the difference, will read up.

Bpath, I don't have either of those items.

KSWL, doubt it, because it is white cotton duck. Would be odd. and difficult, to wipe with a wet rag. Do I have to bleach? Wanted to try vinegar.

Neko, that one did have a pattern, but the others are random "patterns." It's not really a logical or tempting place to sit in a wet suit, and certainly eight people didn't do that.

The heating and cooling split systems have a drying feature.

Confession - I don't know what a split system is.

Lucille, we have been here most the time the last 3+ weeks, and the day or two we were gone no one was here.

What kind of heat or cooling do you have, and does it circulate any air.

I don't know, i have to admit. But, we have no A/C on the first floor. We have central air on the 2nd and 3rd floor, but that is very rarely used; maybe 5 nights a year.

Spring,

May be. But I don't see it anywhere else.

Hallett,

It's so funny you say that. Just today, DH and I were acclaiming the fabulous weather we have been having, and one thing I said was that, in CT, in July and August, when it is hot it is almost always sticky/humid, but it never feels humid here. To which he said "yes, which is so odd, because you would think it would be more humid here than inland CT." We are oceanfront in Southern Maine. I know you are going to say "well duh." But we have not had any issues with mold or mildew and it doesn't feel damp to us, and our home is up on a rise ... its not like we are getting seaspray!

I am thinking that maybe we think it is not humid because to me that means 95% humidity. Maybe we never have that sticky feeling, but instead have sort of constant, low grade humidity?

Odd though, that we have had this home nearly 10 years without this issue.

Another thing... see the window seat with all the pillows? No mildew there, just checked.

I think it is all about the slipcovers. I have used them before, but not often and probably more in the wintertime.

I’m up (down?) in Eastport which hovers around 80% humidity when it isn’t foggy or actively raining;) so while that’s less than I’m used to outside in Georgia it’s much higher than I’m used to Inside with good climate control. Wash them (oxygen bleach) and leave them in the sun to dry, it might never be a problem again.

All the cushions on the window seat are okay?

If its humidity than more than just those chairs would be affected.

Oh wow, you are really in Maine; about 5 hours Northeast of us! My DH calls us "Maine light" or NH North, because we are so close to Boston here compared to the huge expanse that is Maine!

This mold issue is really a conundrum, because my DR adjoins my LR where my sofa and 2 armchairs are slipcovered, with nary an issue in 9 years. I am reminded though that I have a large metal tray in the DR that often develops rust, my flatware in the kitchen is set out in canning jars and the knife blades sometimes rust (I blame people putting it away wet from the D/W) and once we had to clean rust on the trim of our beloved La Cornue in the kitchen. So it may be more humid that we realize just because it is never that 95temp/95 humidity we know from further South. I wil buy a hyrgometer to see (thanks, @bpath)

I Shouted the white slip covers, let the Shout soak in and dry, and then put them to soak overnight in a vinegar solution. Hoping not to use bleach.

The chairs themselves I vacuumed and are sitting in the sun. The fabric seats are destined for the treatment below, excerpted from here ( https://embassycleaners.com/diy-tips-for-removing-mold-and-mildew-from-upholstered-furniture/ )

To clean mold and mildew from upholstery, follow these steps in a well-ventilated area:

1. Take the item outside and into direct sunlight because sunlight kills the mold and prevents it from spreading through the house as you clean the upholstery.
2. Sweep any visible mold off the fabric with a broom, but don’t sweep unaffected areas as this can spread the mold.
3. Using a vacuum with a filter, use the brush attachment and vacuum clean the upholstery. When you finish vacuuming the upholstery, empty the vacuum canister or discard the vacuum bag to prevent the spread of mold spores back into the air.
4. To remove a large quantity of mold from upholstery, mix mild soap or detergent and water until it’s full of suds then wipe only the suds onto the upholstery and rub thoroughly into the fabric. Follow by wiping the area with a clean, damp cloth to remove the soap.
5. Allow the item to sit in direct sunlight for several hours to ensure elimination of the mold and mildew.

Once the item has dried, examine it for mold and check for mildew smell, and if any remains, spot treat the affected areas with equal parts water and rubbing alcohol in a cleaning solution. If you don’t want to use rubbing alcohol, use equal parts water and white vinegar, spray the fabric and let dry in direct sunlight. (I will do this even if there are no spots left after steps 1-5, just to be on the safe side.

I am surprised you haven’t had any issues before now. Our house isn’t on the water; it’s 2-4 blocks from the water depending on which way you turn. Before we had central AC installed, our baseboard radiators had rust, upholstery sometimes just had that mildew smell. It’s probably at least partly because we renovated the house and made it super tight with hurricane windows etc…but we also added AC which we just run every so often to ”dry out” the house. (And we have used it more in the past month, with the heat and humidity, than we probably had in the previous 5 years total!)

A couple of years ago, we arrived at the house after, I don’t know, maybe a month or so of not being there, to find about a million dead termites on the first floor, all in the bathroom. I was ready to burn down the house. Long story short, the issue was the humidity level in our basement (which is only a crawl space) and we now have a dehumidifier running down there all the time.

Your story is a mystery — I hope you figure out how that happened! We haven’t had any visible signs of mold/mildew on any upholstery or pillows.

All the cushions on the window seat are okay?

@eld6161, They are. The pillows are fine, and we removed the long bench cushion and it is fine, too.

Which leads me to suspect it is all about slipcovers trapping moisture, but that didn't happen in the next room over where most of our LR furniture is slipcovered.

Humidity is relative and 70-80% can feel dry at moderate temps or with a breeze. The warmer the air is, the more humidity it can hold, so 70-80% at warmer temps is more moisture. Byt at lower temps, the air holds less and it can collect on surfaces easier. The fact that you have AC on two floors means the air on those two floors is getting dehumidified to at least some degree by the AC. We have a two stage AC that will run at low speed to dehumidify to a specified setting to help with mold and mildew allergies. The air that freely circulates with the two other floors (guessing the stairwell is closer to the LR and the DR is at least partially closed off) gets some of the same benefit. But the DR may be further, have less air mix and hold just a bt more moisture. Recent storms may have been just enough to push you over the edge. A fan or dehumidifier could help.

It sounds to me like the slipcovers are made in a way that make them less breathable -- whether it's the weave - or even the weave on top of another weave, or a finish applied to the fabric -- could be in manufacture and not by you -- something is causing them to trap just enough moisture. The damp bathing suit suggestion sounded like a possibility, but apparently not.

We use Oxyclean to soak and remove mildew -- I find it more effective than vinegar, safe for colors and seems to be best with a drop or two of Dawn or laundry detergent. You may be surprised how much color (grey) comes out in the water. Alcohol reminds me that we have some unscented hand sanitizer that is essentially a high percentage (over 90) alcohol. I might try that because I have it -- but alcohol can dissolve some finishes, so you would need to protect the wood and test to see if it removes color from the fabric before going full scale.

Personally, I would remove the buffalo check covers, carefully clean them and replace the cushions underneath. Any kind of foam or padding would be very hard to effectively clean and eliminate mildew. If sunning and vacuuming doesn't work, that looks like a reasonable option with those seats - nothing too tricky about them, just a bit tedious.

You can get an inexpensive thermometer/hygrometer combination and check the humidity levels in that room. It would be a good thing to know and monitor since you've had this issue,

Hope you can get everything cleaned and back to normal.

I'd wash the slipcovers hot with bleach or oxy or whatever with the intention of removing any possible fabric treatment they might have. Uhhh and the mildew too.

If these chair seats have a plywood backing (instead of webbed), then ambient moisture is more likely to get stuck in them than it would something like a sofa since the one side is solid. The moisture has fewer directions to air out...

Mnt, I am familiar with coastal Maine. The entire region can be very humid, and even if your home is on a rise and not on the shoreline, it doesn’t much matter. Sea spray is not required ;)

Your house will have humidity in it, just by virtue of its location and the open windows and doors. It will not necessarily feel ”humid” but even on a nice sunny day you will have marine humid air coming into your home. So you have air with salt. Salt attracts moisture as certain other molecules. It is interesting that some of your flatware also gets specks of oxidation (more on this in a minute).

When you are away, the house is probably closed up — windows shut, heat off (or set to 50 deg F), and there is likely no fan and no one moving about to create any drafts or circulation of air. Still air with a marine component.

I’ve lived smack on the coast there with all but the tide coming in. In summer, windows were usually open. I could hear clams sighing and seaweed stretching. Never any mold on things or oxidizing flatware because there was constant activity, cirulating air, air currents from just people moving about, even with long stretches of ”socked in” damp weather and fog.

However, the closed up cottage next door got musty because there were long periods where the place was closed up, no renters in it for periods.

That marine air is heavenly, but it sets the stage for oxidation or mildew when no one is living there, even for just a feew weeks.

Looking at the blue plaid chair (very pretty, btw) I discern what I’d consider a pattern in the mildew/mold (dark color). I suspect this reflects the position of a person’s thighs and butt — someone who had sat in the chair. Humans perspire all the time and perspiration, like marine air is salty and will attract water molecules (moisture), even when the person who sat in the chair is long gone.

Because the house was closed up for a while, there were no air currents.

You might be able to run a few dehumidifiers on low, or keep a few fans circulating air. Fabrics and surfaces are different so will vary as to their ability to resist the effects of marine humidity.

As for removing the stains and killing the spores, I don’t think Shout or vinegar will be helpful. Perhaps oxygen bleach in tepid water and neutral detergent. If you cannot machine dry the fabric, line dry in sunlight (perhaps back in CT). As for the stain on the white seat cover — who knows why the mildew made that pattern. No leaking ceiling.

What a lovely dining room and view. And your seat covers are fresh and smart looking.

I hope you can get the fabric cleaned and the humidity/close air problem remedied.

If the stain is gray, it's mildew; black is mold. I suspect it's mildew, which is caused on fabric by getting wet/damp and staying damp for a an amount of time. It was probably caused by having the covers over the cushions, which kept the cushions from drying out quickly.

Interesting, this would indicate that mold growth would occur when the temperature is over 50F, and relative humidity is over 80%. It is 70F/68RH in the DR right now. I will keep an eye on it.

I tried scrubbing them as per above, and tried rubbing alcohol. The fabric was unfazed by my ministrations. We are removing the covers to see if they can be washed; there is no visible mold on the foam but we have them sitting in the sun.

We happen to have a bolt of extra fabric that would be enough to redo all of the chairs in the buffalo plaid

I could hear clams sighing and seaweed stretching.

LOL

@petalique

I might try fans just for good measure. The house has been occupied since mid June with the exception of 2 days.

If these chair seats have a plywood backing (instead of webbed), then ambient moisture is more likely to get stuck in them than it would something like a sofa since the one side is solid. The moisture has fewer directions to air out.

@Fori Good point! They are plywood.

The air that freely circulates with the two other floors (guessing the stairwell is closer to the LR and the DR is at least partially closed off) gets some of the same benefit. But the DR may be further, have less air mix and hold just a bt more moisture. Recent storms may have been just enough to push you over the edge.

@lascatx I think this is a good assessment. Who knows why, but I think it was the combo of these two fabrics

Thanks all!

I'm glad you caught it when you did -- hope that will be the end of it.

Notice that the temps in your humidity and mold growth chart are in Celcius -- so a little less than half of Fahrenheit.

Yes, of course, which is why I said , above "Interesting, this would indicate that mold growth would occur when the temperature is over 50F."

OK -- But I still question the 80% humidity. The CDC suggests humidity levels not higher than 50% in your home to avoid mold and mildew. The EPA says indoor idealas are 30-50%. In our humid climate, we target 50-52%. I've seen letting it get higher has a negative impact on my allergies.

petalique,

I could hear clams sighing and seaweed stretching. That's a bit of poetry and it's brilliant!!! Are you a writer?.

Well, I have gone down a rabbit hole on humidity.

We have been experiencing daytime humidity in the high 40s with mid to high 70s temps for the last several days. When it is not raining, that is typical summer weather for our microclimate here. One thing I didn't realize before though is how much humidity can change within the same day.

Anyway, I read that indoors it varies not only from room to room and but within a room?! Last night the RH humidity in my DR was 62 on the mantle over my fpl, and 54 on the DR table itself.

I've read more than I ever wanted to know about humidity, relative humidity, dew points, ventilation and mold and mildew (which is just a type of mold). I have been inspecting nooks and crannies all over the house to make sure it is not occurring elsewhere. We have never had any mold anywhere in the house before and we don't have any of the ancillary problems (like insects, eww) associated with too-high RH. Our (1904) house was not winterized until 2012, when the POs put in all new windows, insulation, etc. We have been happy with the HVAC and as I said, very rarely use AC, for sleeping. The house smells pretty fresh, probably because we redid the floors and walls pretty much head to toe.

So I conclude our humidity issues must be very sporadic (tee hee) and isolated. In this instance, I think it was a combination of a spate of rainy days, coupled with our leaving the door open to our screened porch. Usually air flow into the house drops in humidity as it warms up, but it may have been the same temp inside and out in which case we may have imported some humidity inside.

I don't know if I will ever try those slipcovers again but certainly not when its humid.

Does the photo of the mold on the slipcover match the photo of the mold on the buffalo plaid - i.e. are they from the same chair?

Yes, at least I am pretty sure.

Reason I ask is because the patterns of mold look different. Slipcover is a round, chair itself different. I'm late here and you've rec'vd great info from everyone. Just looks like someone may have sat on the chair itself and the cover looks like something round was sat on it.

Your fabric choices are always quality and natural ones like cotton, linen. Not sure how they would trap moisture. If they did, why aren't your other covers doing it too? Don't mean to beat a dead horse here!

Why is everyone ignoring those of us who are saying we think this is mildew, not mold ? The stains look like classic mildew on fabric to me. Both of them are fungi, but mold is raised, mildew is flat. Treatment for mold and mildew are different. Apparently, cleaning vinegar will kill mildew to it's roots.

You said the long bench cushion is fine? Doesn’t it also have wood under it?

@woodrose77 Sorry, I was composing my manifesto back there and I didn't see your post right before mine. I do think you are right, it is mildew. I was under the impression that mildew is a type of mold and they are cleaned the same way. In any event, the white slipcovers came out clean with shout, a soak in vinegar, and a wash in cold water.

The blue and white check cushioned seats have been removed (except for 2 that are ok). Those did not respond to anything I have done, including a long soak in vinegar followed by a hot wash. They have now been soaking in bleach all day and are now washing. We shall see.

@Arapaho-Rd The interplay between absolute and relative temperature and umidity, and between ventilation, air exchange, leakage and pressure, is a pretty complex set of interactions. I don't really know what happened, but I don't think it was someone sitting down in a wet bathing suit, given who has been where when and the timing of when I noticed this. It was also on more than one chair.

@Olychick That is correct. And, being a windowseat, it is closest to the humid exterior air.

Sorry, I should have written more. If the window seat has a wood base and is closest to the humid air, I'm wondering why it is fine and the dining seats have mildew? I still can't help think that people sat on the seats with wet clothes/bathing suits. Maybe the next day the seats were still wet, so they sat on dry ones, explaining why all the chairs might be affected. But you're on site and have more info.

No, i got your point. It is close to humid air, but also closer to the movement of air. So who knows?

I still can't help think that people sat on the seats with wet clothes/bathing suits. Maybe the next day the seats were still wet, so they sat on dry ones, explaining why all the chairs might be affected.

In a vacuum, this sounds plausible. But, as you say, I am "on site and have more info." For the last month plus, no one has been here without me. I never saw this behavior. And I highly doubt anyone would have done so. Not because they are so well behaved (though they are pretty good) but because it is just not where they would choose to sit at random, esp. after swimming. In fact, they only sit in the DR if I serve a meal there, usually dinner, and no one has shown up for dinner in a bathing suit. We also sit there to play games, always after dinner. People use the dining rom pretty much when I force them to, LOL.

I was thinking renters, but sounds like there haven't been any recently.

Correct.

It is an interesting mystery and I suspect you are right -- a bit of a fluke and something you may just avoid by not having the slipcovers left on for extended period or during/after stormy times.

Woodrose, mold is a more general term that covers a broader category. Mildew is one type. From the EPA: Mildew refers to certain kinds of mold or fungus. The term mildew is often used generically to refer to mold growth, usually with a flat growth habit. Molds include all species of microscopic fungi that grow in the form of multicellular filaments, called hyphae.

...and I was thinking renters too! Thanks for straightening us out ; )

I am assuming you keep the chairs pushed under the table, that means there’s really no air movement under there. Leaving the slipcovers added more bulk and even less air circulation and was the tipping point.

My mom had a similar issue once in her house, every thing fine for years. One year she left a long tablecloth on the table. The combo or the tablecloth touching the sests of the upholstered seats was her tipping point for mold. She was very unpleasantly surprised when she pull out the chairs. She never left a tablecloth on the table again and never had recurrence.

Just a thought…..Maybe just keep a ceiling fan on low when not occupying the home. Air circulation may be all that is needed. When people are in the home, air circulates just by body movement.

@localeater, Yes, sounds similar.

@njmomma. No ceiling fan but maybe a box fan.

Maybe overly cautious, but we do not leave our ceiling fans on when we are not at home. There was an instance several years ago where a house caught on fire. The cause was found to be a ceiling fan. the motor had burned out and started smoldering. Thankfully the fire was contained to the attic. We are very careful as to what we leave running when we are not at home.

A great fan is Rowenta ’Turbo Silence’ extreme. Quiet, large-ish fan on a very soiid abd attractve stand. Nice lines.

mtn, didn ’t Fori say something about plywood. Moild/mildew and plywood are sybiotic accomplices, in my mind. Can you poly urethane that spore-y plywood?

I wonder id the fabric was treated with ”sizing” and not washed before being sewn. A lot of us like sewing with bodied fabric (nice, crisp and behaves). Sizing is a starch like glaze.

Sizing is also on practicaly any fabric that is new and has not been washed. When you wash a new garment before wearing, you remove the sizing as well as any excess dye or other chemicals -- but it has a lot to do with that sizing. On something to be used on a chair, IU wouldn't be surprised if the fabric had been treated with Scotchguard or something similar.

I love these retro vornado fans, they come in different sizes. I think they'd be perfect for a beach house.

My exact thoughts, very nice!

petalique,

I could hear clams sighing and seaweed stretching. That's a bit of poetry and it's brilliant!!! Are you a writer?.

Thank you yayagal and martinca.

DH reupholstered the seats. The slipcovers are washed and put away. I think a fan would be most useful for when no one is here, but we don't want to leave one on.

I did think of something that could possibly be a factor. A few years ago (maybe 2 or 3?) we had ice damage and got a leak in our DR. We had to remove my lovely FnB wallpaper and then painted. I wonder if that was perhaps not fully resolved? However there is no mildew in that spot currently. Our painter is coming out to look in any event. Don't ask me at what.

I think you just had a low air circulation area (under the table would be less than in the room generally -- you could consider pulling the shairs out and make sure you don't keep a table cloth on when not in use). I don't think you would have something on the chairs from an earlier issue in the wall without finding something visible or at least being able to feel moisture on the wall or floor below it. The pattern on the slipcovers would echo where people sit and slight impressions in the cushions. If you ever look at a plastic bag with condensation inside, it will gather in the low spots -- water will condense in high spots, but travel and settle in lower spots, even if not in visible amounts. That is consistent with the pattern you had and you had storms -- more humidity in the air and no AC there. May not normally happen, but a combination of things could bring it together. May never happen again, but you know what be aware of and watch for -- how to better avoid it. Best thing is that you seem to have caught it early while it could be reversed.

I wish I had taken more photos, but the only round pattern was on one slipcover, the rest of the slipcover mildew patterns were random and so were the underlying seat cushions.

Funny, I have never once used a tablecloth on this table, but I was thinking of getting one next year. I thought it might encourage more use of the room. I like the coated cotton ones you always see in France, eg: