Sunlight exposure & DOS?

SoapMakingForum

Help Support SoapMakingForum:

BlackDog

Well-Known Member
Joined
Jul 8, 2015
Messages
582
Reaction score
842
When I left this soap sliver two weeks ago, it was white and purple. Is it DOS, and could it have been caused by sunlight?

A little background info: we often stay at my father in law's farm on weekends in the summer. There's a guest bathroom upstairs that only ever gets used by my husband and me. I leave tester bars of my soap there for hand washing. There's no shower in there and it's air conditioned full time.

I have 4 or 5 bars of this soap at home and they are in great shape. About 7 months old and no signs of DOS.

I left this soap end in the guest bath 2 weeks ago, used it a few times, and when I came back yesterday, I found this orange horror show.

The only thing I can think of is that the sink in this bathroom gets a lot of direct sunlight during the day.

I have only had DOS on one other batch, but it developed slowly and looked like tiny orange spots. I don't know what to make of this.

1467459733800.jpg
 

DeeAnna

Well-Known Member
Joined
Feb 20, 2013
Messages
13,471
Reaction score
19,386
Location
USA
Yes, UV energy in sunlight can affect the appearance of soap. That doesn't mean the change is DOS necessarily, although that's a possibility. UV can also cause colors and fragrances to morph.

Another thing that can affect soap is simple use. Contaminants on the hands and in tap water can discolor soap and trigger rancidity. In my experience, that is more often the culprit, especially with a bar of soap that's been used and then been left undisturbed for some time.
 

BlackDog

Well-Known Member
Joined
Jul 8, 2015
Messages
582
Reaction score
842
Yes, UV energy in sunlight can affect the appearance of soap. That doesn't mean the change is DOS necessarily, although that's a possibility. UV can also cause colors and fragrances to morph.

Another thing that can affect soap is simple use. Contaminants on the hands and in tap water can discolor soap and trigger rancidity. In my experience, that is more often the culprit, especially with a bar of soap that's been used and then been left undisturbed for some time.
Hmmm I had not heard that about UV causing colors and fragrances to morph - I know people who use natural colorants try to keep them out of the sun, but I hadn't realized it might affect micas or TD.

I think that is maybe a more likely explanation than hand or water contaminants in this case, since I also leave bars in the more frequently used downstairs bathroom and in the kitchen, neither of which get the direct sunlight that the upstairs bathroom gets. I've never had this issue with bars I've left in those rooms.
 

DeeAnna

Well-Known Member
Joined
Feb 20, 2013
Messages
13,471
Reaction score
19,386
Location
USA
Well, you didn't say anything about what you used for colorants, etc. so I was replying in a general sense. More specifically, no, I doubt UV would affect TD either. Can't say for sure about mica -- depends on the colorant put on the mica more than the mica itself. Neons and blue colorants might well fade. Botanicals, certainly.

"...bars in the more frequently used ... never had this issue with bars I've left in those rooms. ...."

Which lends even more support to my last point -- "...Contaminants on the hands and in tap water can discolor soap and trigger rancidity. In my experience, that is more often the culprit, especially with a bar of soap that's been used and then been left undisturbed for some time...."

But test the theories yourself so you know. Put the guest soap under a cover that excludes light and see what happens.
 
Last edited:

Susie

Supporting Member
Joined
Aug 1, 2013
Messages
9,715
Reaction score
9,221
Location
Texas
You need to sniff that orange soap. If the scent of rancidity is not there, it is not DOS.
 

BlackDog

Well-Known Member
Joined
Jul 8, 2015
Messages
582
Reaction score
842
Well, you didn't say anything about what you used for colorants, etc. so I was replying in a general sense. More specifically, no, I doubt UV would affect TD either. Can't say for sure about mica -- depends on the colorant put on the mica more than the mica itself. Neons and blue colorants might well fade. Botanicals, certainly.

"...bars in the more frequently used ... never had this issue with bars I've left in those rooms. ...."

Which lends even more support to my last point -- "...Contaminants on the hands and in tap water can discolor soap and trigger rancidity. In my experience, that is more often the culprit, especially with a bar of soap that's been used and then been left undisturbed for some time...."

But test the theories yourself so you know. Put the guest soap under a cover that excludes light and see what happens.
Sorry, I wasn't clear on what colorants I used in the original post. Read my mind, DeeAnna! Jeepers!

Now I'm tempted to take unused slivers and put them in the sun. I feel some experimentation coming on.....
You need to sniff that orange soap. If the scent of rancidity is not there, it is not DOS.
What exactly does rancid soap smell like? My only bars that have DOS currently are developing very slowly - like 2 or three small spots over a few months, and it's not affecting the smell of the soap.

This orange mess in the original post smells "off" but not horrible. And I can still smell the FO that I put in it.
 
Last edited by a moderator:

lenarenee

Supporting Member
Joined
Jan 14, 2014
Messages
3,713
Reaction score
3,325
It stands to reason that it could be sunlight since quality oils are supposed to be bottled in dark bottles and stored in dark places.
 

Susie

Supporting Member
Joined
Aug 1, 2013
Messages
9,715
Reaction score
9,221
Location
Texas
Rancid soap smells like rancid oil. I can't describe it any better. Can anyone help?
 

earlene

Grandmother & Soaper
Lifetime Supporter
Joined
Apr 30, 2016
Messages
8,168
Reaction score
8,445
Location
Western Illinois, USA
When I first started soaping I read some site in the 'net that said you could 'clean' rancid oil using salt and that it would be usable. I followed the instruction and the oil did smell much better, so I used it in a very small batch of soap. That soap turned rancid and orange in a very short time, well about 5 months I think, so maybe not such a short time. But the smell was just awful. I think it was worse than plain old rancid oil, but then perhaps that's because at least rancid oil is usually in a closed container. whereas the soap was not. It was an interesting experiment, but I doubt I'll be bothering with rancid oil again.
 

DeeAnna

Well-Known Member
Joined
Feb 20, 2013
Messages
13,471
Reaction score
19,386
Location
USA
To me, mild rancidity smells a little musty and dusty like an old mildewy basement mixed with a slight sour tang like milk just starting to go bad. It's not a hugely nasty strong smell until the rancidity is really bad, but it's not attractive either. You say the bar smells "off" and that's a telling word to use for rancidity as I've seen on soap.
 

Latest posts

Top