The Dreaded Spots of the Orangeness!

Geranium Patchouli soap with DOS

So you've made a beautiful batch of soap and it is hanging out on the curing rack, evaporating out its water and whatnot. Over the next few weeks, you lovingly check on it and marvel at this wonderful thing you made.

And then you see it. An orange-colored spot - or maybe several spots - marring the pretty surface of your soap and seriously harshing your soap buzz.

What is this ugly plague that is plaguing your soap with its plaguey plague?

It's - dah, dah, DAH! - DOS. No, not the ancient computer operating system. 

Dreaded Orange Spots.

You may remember this Geranium Patchouli soap I made about 16 months ago. I still have some bars from that batch hanging around, and I went to grab a bar recently. I usually let the soap bars cure on my curing rack for 6-8 weeks and then store them in paper bags and it seems to work out just fine. This time, though, the bar I pulled out felt wet and beads of glycerin dew glistened on its surface. 

Handmade soap naturally contains glycerin, which attracts moisture from the air. Humidity can increase the likelihood of glycerin dew, and it can get awfully humid here in Louisiana. It was interesting that none of my other batches that were stored similarly developed the same issue. At any rate, I wiped the afflicted bars dry and let them hang out some more on the curing rack. Now the glycerin dew is gone, but the ugly rust-colored spot remains.

So what causes DOS? Oftentimes it is caused when oils are exposed to oxygen and oxidize, resulting in rancidity. Every oil has a shelf life and some oils have shorter shelf lives than others. DOS can appear at many points during a soap's life - during the cure time or months later, as was the case with my soap. Old oils or oils with short shelf lives may contribute to DOS. And it's sometimes difficult to know how long an oil has been sitting on a store shelf before you buy it. Get your oils from quality vendors that replace their oils frequently to ensure that they are as fresh as possible and pay attention to expiration dates. (To see a comprehensive list of oils and their properties - including shelf life - check out this Soap Queen post.) Some oils - such as canola, grapeseed, and sunflower oils - have a reputation for contributing to DOS, although I haven't soaped with any of those oils and therefore can't comment on my own personal experiences with them.

Oil storage is important. Some short-life oils are best kept refrigerated, and it's always good to store any oil in a cool, dark place away from direct sunlight. Another tip is to transfer oils to smaller bottles as you use them up so that there is less contact with oxygen and therefore less risk of oxidation. Some soapmakers also add antioxidants such as rosemary oleoresin extract (ROE) or Vitamin E to fragile oils to extend their shelf lives.

Higher superfat percentages can also contribute to DOS. "Superfat" refers to the amount of oils that do not interact with the lye and remain unsaponified and sorta free-floating in the finished bars. Most soapmakers factor in a small percentage of extra oil in their recipes to create a more nourishing bar of soap. Some soapmakers advise keeping superfat percentages to 5% maximum (with the exception of recipes containing all or nearly-all coconut oil, which need a higher superfat of up to 20%). I usually use a superfat of 7% in a typical recipe with no problems, but could it have been an issue in this batch? Or was it something else? Perhaps I should experiment with a 5% superfat.

Water is also another important soapmaking ingredient. It's a good idea to use distilled water since tap water may contain minerals that could oxidize and cause DOS.

The curing environment is also important. Let your soap fully cure in a cool, dry place with plenty of ventilation. During the curing process, water evaporates from the soap and the moisture needs to be able to escape. Wire racks are great for curing, just make sure that the metal is coated so that it doesn't rust - rust can exacerbate DOS. If your curing area is particularly humid, a dehumidifier may help.

What caused DOS in my case here? Dunno. Could have been the oils, humidity, storage issues, or something else. It seems that so many soapmaking problems remain mysteries even when potential culprits are identified. I can't point with certainty at any one factor or factors. Hopefully, though, I can better avoid DOS in the future by keeping these tips in mind.

So what should you do if your soap gets DOS? Don't panic. The spots are rather ugly and the soap may smell a bit off, but it is merely an aesthetic issue. I wouldn't want to sell or gift these bars with DOS because eww-gross, but they're still fine to use.

At about the same time I was cogitating on this post, Anne-Marie wrote a great one about DOS on the Soap Queen blog. And also check out this helpful post by David Fisher for more info on DOS.

Have you experienced DOS? What are your thoughts on what causes it and how to prevent it?