Help! Powdery stuff coating my shelves

Recently we moved my bookshelves, which were built about 16 years ago, into another room and had new bookshelves made to match, by a different carpenter, to fill in the gaps. Both sets are covered with cherrywood veneer. When the work was finished, I cleaned the shelves (with Method all-purpose cleaner) and polished them with wood oil before getting my books out of storage and starting to shelve them which all (due to time constraints) took quite a few weeks. Because we live in the tropics, I have electrical dehumidifiers (essentially, a low level heat emitter) in each cupboard.

Towards the end of my shelving phase I noticed a grey, powdery substance on the wood surfaces, both vertical and horizontal - including on the underside of shelves. It seems to be worse/ solely in the older cupboards and only on the insides. I thought it might be mould at first but the dehumidifiers are working. It wipes off if I just swipe my finger along it and doesn't leave a mark. I'm wondering if it might be a chemical reaction from the cleaner or polish/ combined with the dehumidifying. There is a musty smell in the cupboards (they have glass-fronted doors) in spite of the fact that I wiped down the books before I reshelved them.

Does anyone have any idea what might be causing this? And what I might do to get rid of it? Thanks.



For some reason, it seems to be forming/ depositing in lines. I've ringed in one photo the place I swiped my finger through it (it feels like talcum powder) a few weeks ago and it doesn't seem to have come back in that spot.

And it seems to affect only the three older cupboards in spite of the fact that they are in two different rooms and the new cupboards are interspersed between them. This isn't the first time it's happened. The last time, I asked the carpenters (who built the older cupboards) and they just laughed at me and said it was dust. It seems weird behaviour for dust, especially in closed cupboards which have just been cleaned.

Help, please.

I'm not an expert, but it sure looks like mold to me. :(

The first thing I'd do is measure temperature and humidity both in the room and in the bookcases.

You should seriously consider freezing those books. (Apologies in advance for the man-splaining.)
Remove as much mold as you can (preferably outdoors) and place the books in a large freezer-safe plastic bag that seals at the top (zip-loc variety), removing as much air as possible before closing the seal entirely, and place the bag in a freezer for three or four days, depending on the bulk of the books -- you want to ensure that all of the volume gets below freezing. When you take them out of the freezer, wait at least 24 hours before you open the bag. You don't want condensation forming on the books.

As for the bookcases, you need some form of anti-fungal treatment for them.

What a nuisance! I hope you can get it under control.

I’m so sorry this happened to you. I live in Florida and my dehumidifier is going gangbusters all the time. We had a leak from a hurricane and I’ve been on guard for mold ever since. 😢

Thanks everyone, for the tips and the sympathy.

😱😵‍💫 AAAGGHHHH!!! I’d just about convinced myself it’s not mould, especially because I’ve just cleaned and polished 8 bookcases containing 68 shelves and individually wiped down each book that came back from storage (around 500) over the last few months in spite of the fact that my dermatologist banned me from doing any cleaning.

As for freezing the books - maybe it’s time to get that stand-alone freezer I’ve been fantasising about rather than try and find space between the ice cream and the bacon …

In the meantime, I need to find a dark corner to sit and think calming thoughts.

>6 humouress:

I don't suppose you live anywhere near these folks: https://midwestfreezedry.com/

Maybe you could find a similar business near you?

>7 lilithcat: Only about halfway around the world :0) At the moment, I haven't seen mould on the books themselves though many of them are brown around the edges of the pages and there is a musty smell in the cupboards - so hopefully I won't need their services. But thanks; I'll know what to look out for if I do.

The story of my struggles with my bookshelves over the past 15 odd years is here: https://www.librarything.com/topic/84489#n6163858

I was hoping that it isn't mould but I think you're all right; even the bookcase without that many books in smells musty when I open it. If it's not termites in the tropics, it's mould. If it isn't mould, it's dry wood termites. If it isn't them, it's 😡🤯... I give up.

Question (for any wood experts): could it be the polish that is giving the mould some kind of foothold? I usually polish the shelves after cleaning them; it smells nice (this particular one is lemon-scented) and I assumed it gives a protective coating. The veneer itself is quite smooth. I don't know why the whatever-it-is forms in lines like that; mould is usually splotchy in my experience.

When I initially looked it up I found something about the glue used with veneer coming through and forming deposits (of course, I can't find it now) which is why I haven't been pulling my hair out about this until now. Does anyone know anything about that?

I don't know about wood polish, but I feel like it wouldn't cause a musty smell. The smell is a dead giveaway.

>11 reconditereader: The smell is a dead giveaway. 😭 It looks like I can't deny it any more.

What beats me is how it happened even with two humidifiers in each cupboard. Granted that even after I had to remind them to come back and install them as agreed, I didn't realise that the carpenters hadn't bothered to turn them on. But I switched them on and they have been chugging away for the past few months.

ETA: I was wondering if the polish gives the mould some kind of substrate to feed off. I'm (fairly) sure the veneer is genuine wood but it doesn't seem porous. And the powder falls off quite easily, not as though it's dug 'roots' in.

Can you access a friendly microbiologist who would have a really close look at your ‘dust’? I would have thought that a firm microscopic diagnosis was possible.

The polish might be trapping moisture against the wood. I gave up on polishing a long time ago when living in an extremely humid climate, because the standard furniture polish left a tacky (to the touch) film that was difficult to remove.

Regular dusting on its own has usually been good enough. We use food-safe wood cleaners and conditioners, when more is needed. My guess from watching what happens to the cleaning products on their own is that the food-safe cleaners are a little better with resisting mold in the more humid environments.

>13 abbottthomas: That might be something to look into, thanks.

>14 aspirit: At least that will cut the potential work in half if I don't polish the shelves after defungusifying them.

I like the way polishing brings out the depth of the grain in wood but anyway it doesn't do that with this veneer.

Living in a very humid place, I've found it's very hard to predict what the mold will and won't decide to live on - sometimes two pieces of wood right next to each other that seem identical, one will be affected and one won't, even with the dehumidifiers running all summer.

Some of your photos actually do look more like the finish reacting weirdly with air conditions, tbh, but if it wipes off easily and you have a musty smell I'm willing to agree with the others. An issue with the finish or polish is more likely to directly mar the surface.

You can anti-mold wood treatments that go on like polish, and I've had fairly good luck with them, but it depends on how sensitive you are about what gets near your books - I don't know if any of them are archival-certified.

Thank you for all the suggestions. I am currently pondering the logistics of getting books into the freezer (which has limited space, anyway) although I haven't spotted growths on my books ... yet.

Here's something about cleaning mould off books:
https://www.greenmatters.com/health-and-wellness/how-to-protect-books-from-mold

https://www.wikihow.com/Remove-Mold-from-Wood-Furniture

Natural mould removers:
https://www.bhg.com.au/natural-mould-removers
https://moldguide101.com/mold-removal-products/essential-oils/
https://lavendertips.com/does-lavender-really-help-against-mold-spores-exploring...
https://greenorchardgroup.com/5-air-purifying-essential-oils-that-kill-mold/