DOS from sunlight exposure

[Mobjack Bay]

Here's a very clear example of DOS due to sun exposure. I left the two smaller pieces of soap sitting on a cart next to a sliding glass door and forgot about them for a couple of weeks. A few weeks ago, at least, I moved them back to the soap rack. They would have gotten strong morning sun for a few hours a day. The two longer pieces were out of the sun on my soap rack. The batch was made late last year.

 

[szaza]

Oh no that's too bad.. it's really pretty soap!! But thanks for the heads up about sunlight and DOS!
I recently experienced something similar with some 100% CO soaps that were sitting in the window sill for +-10 months. There's not really clear DOS, but the smelly smell is there, it's not nice soap anymore. I should go check on their twins in the basement

 

[amd]

I had that happen with food puree soaps (carrot, pumpkin, potato) and occasionally an aloe soap if I did a lot of shows in the summer. Always keep your soaps in the shade!

 

[DeeAnna]

Soapsmith did an experiment that looked at how edta, bht, and citrate as well as muslin bags can hep reduce the incidence of DOS. The soap she didn't treat and left exposed to light turned out similar to what you're seeing with your soap, M.B. Kinda cool stuff, actually, even though I don't like DOS.

http://soapsmith.blogspot.com/2015/09/soapsmith-dos-experiment.html

 

[Mobjack Bay]

More DOS for your viewing pleasure...

A few months ago I discovered these color test blocks that had been sitting in the open air and light on the top shelf of my soaping rack since Dec 2019. The bottoms, which were sitting on a paper towel over the wood of the shelf, look fine. The sides and tops, which were exposed to air and light, not so much. I’ve been archiving a bar of most of my batches for over two years now, but never quite got around to tucking these away. The recipe had EDTA at .25% of batch weight and the liquid oils had ROE added. It looks like that was not sufficient to protect these exposed soaps. DOS is a very rare occurrence in my archived soaps, even the earliest ones that were made without a chelator and antioxidant, and when I do see DOS, it’s usually in a small spot, not across edges like in the test blocks. I archive soaps individually in small paper bags inside a larger box.

edited to clarify that ROE was added to the liquid oils

 

[Peachy Clean Soap]

Soapsmith did an experiment that looked at how edta, bht, and citrate as well as muslin bags can hep reduce the incidence of DOS. The soap she didn't treat and left exposed to light turned out similar to what you're seeing with your soap, M.B. Kinda cool stuff, actually, even though I don't like DOS.

http://soapsmith.blogspot.com/2015/09/soapsmith-dos-experiment.html

Fantastic info' worthy of saving to my reading list for future reference. I'm now interested in "Muslin" for storing my soap's, of course continued use of a preservative. Thx appreciate your post.

 

[The_Phoenix]

Speaking of DOS. I experienced a DOS soap at my parents’ house a few weeks ago. Someone had gifted my mom a bar of soap and has been wrapped in an organza bag. She doesn’t remember who got it for her, or how long she’d had it, but I’d say a few years.

Wish I had taken a phot of it. It stank! And only the interior swirl was DOS. The rest of the soap was extremely brittle and horribly dried out. It didn’t smell like anything. Except DOS.

I did shower with it for fun and curiosity. Nice lather. But the stink stayed in my skin. Ewe. I’m guessing the maker used canola oil because it smelled like rancid canola oil. Pretty sure it’s an oil I’ll never soap with.

 

[DeeAnna]

I gave a bar of soap to a friend early on in my soapmaking misadventures, well before I'd started to use EDTA chelator. Some months after that ... maybe a year or so later ... I guess we got to talking about my soapmaking hobby and how she was so proud of what I'd been doing.

She showed me the bar I'd given her, and I was horrified because it was nasty with rancidity. I don't know if she quite realized it had serious problems -- she didn't say anything about the appearance.

I snuck this bar home in utter embarrassment -- I just couldn't let her keep it. I compared her bar to a sample from the same batch that I'd kept in my "bone pile" of samples. Imagine my bafflement -- my bar looked fine while hers was horrible.

That was a sharp lesson that things that work well for the soapmaker's soap doesn't always apply to the customer's soap, even though the bars are from the same batch. I started studying ways to prevent problems like this, especially when my soap lands in other people's hands. That opened my eyes to the use of chelators and antioxidants.

 

[Peachy Clean Soap]

I gave a bar of soap to a friend early on in my soapmaking misadventures, well before I'd started to use EDTA chelator. Some months after that ... maybe a year or so later ... I guess we got to talking about my soapmaking hobby and how she was so proud of what I'd been doing.

She showed me the bar I'd given her, and I was horrified because it was nasty with rancidity. I don't know if she quite realized it had serious problems -- she didn't say anything about the appearance.

I snuck this bar home in utter embarrassment -- I just couldn't let her keep it. I compared her bar to a sample from the same batch that I'd kept in my "bone pile" of samples. Imagine my bafflement -- my bar looked fine while hers was horrible.

That was a sharp lesson that things that work well for the soapmaker's soap doesn't always apply to the customer's soap, even though the bars are from the same batch. I started studying ways to prevent problems like this, especially when my soap lands in other people's hands. That opened my eyes to the use of chelators and antioxidants.

Familiar thread' In my early soap beginning days ( going on three years ) i'm just a babe to many of you soap veterans w/ years of experience. I didn't use any chelators or antioxidants of any kind, I didn't think it was truly necessary. I coulden't of been more wrong, I use them now .

 

[Mobjack Bay]

I should have added above that the test bars also had ROE added to the liquid oils. The recipe was 60% tallow and lard with coconut, olive and castor oils. It’s not a recipe that I would consider to be DOS-leaning, but then I also never feel 100% confident about olive oil.

It’s interesting to me that I never see DOS In bars that are in use. I have loads of them around my house, including a half dozen or more that were made back in the summer 2019. They are exposed to air, normal house lighting and some indirect natural lighting, but not to direct sunlight.

 

[DeeAnna]

The rancidity is being washed off bars that are in use, assuming there is any rancidity happening.

 

[szaza]

I once tried to make a soap last longer by only using it every once in a while (it was a gift and I wanted to treasure it). By about the 5th time I wanted to use it, the soap had become rancid, while another bar that I had stored was still perfectly ok. Apparently that soap didn't enjoy the light and humid conditions of our bathroom.. I might have made it last longer if I actually used it more

 

[szaza]

Oh no that's too bad.. it's really pretty soap!! But thanks for the heads up about sunlight and DOS!
I recently experienced something similar with some 100% CO soaps that were sitting in the window sill for +-10 months. There's not really clear DOS, but the smelly smell is there, it's not nice soap anymore. I should go check on their twins in the basement

I remember going back and checking the soaps that I kept in the basement, but apparently I didn't write back about it. I think the ones in the basement were perfectly fine, but I got rid of them during the move last year, so I can't go back and double check.

 

[DeeAnna]

I once tried to make a soap last longer by only using it every once in a while (it was a gift and I wanted to treasure it). By about the 5th time I wanted to use it, the soap had become rancid, while another bar that I had stored was still perfectly ok....

Used soap often goes rancid faster than unused soap. The dirt and bacteria on your hands and dissolved minerals in tap water are the culprits, in addition to exposure to light.

I agree -- once a person starts to use a bar of soap, the best way to help the bar remain fresh is to use it regularly. Keep washing off that outer layer of soap that may be oxidizing.