Soap makers face a problem called Dreaded Orange Spots, often referred to as DOS. These spots have been widely discussed for decades. As the soap ages, sometimes it developes areas of rusty colored spots. Most people consider them to be a sign of rancidy of the oils. The spots start off as small round dots and will spread throughout the entire bar over time.
Dr. Kevin Dunn, known as the caveman chemist
, is a professor and a soap maker. He has conducted scientific testing with his students on a number of soap making issues including the study of DOS. I attended a presentation by Dr. Dunn at the Handmade Soap Maker's Guild where he spoke about his study results. It was fascinating. I wanted to do my own experiment using Dr. Dunn's recommendations.
On the same day, using the same identical supplies, I made two batches of my Vestal Castile Soap. The soap is 100% certified organic olive oil, distilled water and lye. Nothing else. No fragrance, no color. I did cold process, soaped between 4 & 5% superfat. To the second batch, I added .1% each of EDTA and Sodium Citrate and .05% BHT. These are the additives that Dr. Dunn discussed in his presentation on the prevention of DOS. The EDTA and Sodium Citrate was dissolved in water, the BHT dissolved in warmed oils. Both batches were brought to full gel.
At all times, the test bars were kept together in identical curing and storage situations. They were cured in my soap studio for 8 weeks. One bar of each was put in muslin bags (I have always sold my bars in muslin), and one bar of each was left unwrapped. They were kept, untouched on a shelf in my office at the store. This would be the same retail environment as my soap cart. We only maintain the heat and AC during store hours, so the soap was exposed to some very hot humid conditions during the summer months, and 55 to 60 degree cold during the winter months.
Here are the pictures of the results. As you will note, the two bars with the additives are sparkling white, pristine with no signs of DOS. The wrapped bar with no additives shows one small, very light DOS developing in the upper right hand corner of the bar, the unwrapped bar with no additives is almost completed covered in DOS on all sides. It is also interesting to note the unwrapped, no additive bar shows great difference in shrinkage and cracking.
I have always believed that selling in muslin gives the best protection. I have had bars deteriorate on the display shelf while the same batch bars in the muslin bags stay perfect. When I compare the bars that had no additives, the one that was unwrapped is drastically impacted by exposure to light and air. My belief that muslin is best for my soap have been validated. The results of this experiment also show that simple muslin packaging provided similar protection against DOS as did the chemical additives.
The top bar is the additives in muslin, next is no additives unwrapped, next is additives unwrapped, and last is muslin no additives, note the faint yellow spot in the upper right hand corner of the last bar.
This is the back side of the same bars.
The pictures are not enhanced, they are taken in natural light. I hope this provides some useful information to my fellow soap makers.