Orange spot on a soap

Have you ever heard about orange spot on a soap? I was wondering how it looks like and now I have an answer. I discover this soap in my curing box 1 week ago and to be honest, I was very pleased to discover this orange spot on my soap. I've got a visual experience now.

 I'm curious as well: why this orange spot appears on my soap and how can I avoid them? 

After a lot of research, here what I've found:

• A high amount of unsaturated oil could be responsible of these spots. Indeed, unsaturated fatty acid with more double bonds are more vulnerable to rancidity than saturated fatty acid
• The use of tap water or mineral water is not recommended, it's accelerated the rancidity of saturated oil and encouraged the formation of spots because of metal ions into water 
• The curing period is very important as well. Indeed, a humid room is more favourable of the oxidation of the unsaturated fatty acid

 Many solution can be used to anticipate this problem:

• Using more saturated fat (50% seems to be a good minimum rate) into your soap than unsaturated
• Avoiding to use fragile soft oil as sunflower, flaxseed or hemp oil which are very sensitive to oxidation or reducing their amount in your recipe to combine them with an other unsaturated oil as olive oil (natural anti-oxidant) which is much more stable. The iodine value can help you as well to evaluate if your soap is expose to rancidity or not. The higher the iodine value is, the more vulnerable to oxidation it is the oil and therefor the soap
• Adding NATURAL preservative as Rosemary oleoresin extract (ROE) between 1 and 2% of the total oil. ROE is the most effective natural preservative.The antioxidant activity of rosmarinic acid is stronger than that of vitamin E. Rosmarinic acid has antioxidant, anti-inflammatory and antimicrobial activities. Vitamin C, E and EPP are good anti-oxidant but not for soap.
• There is an other effective preservative for soap, EDTA, but it's a chemical and frankly, I wouldn't recommend you to use that one. It's limited the proliferation of bacterias in soap but ecologically, it's badly biodegradable. In cosmetic, considering as a poison, it's used as a small amount, no more than 0.6%. After, it's up to you. Me, I prefer the natural substitute which works very well.
• Reducing the lye discount doesn't extend the shelf life

Source: Scientific soap making, Kevin DUNN;  Wikipedia; Phytochemicals.info



So now, it's clearer to me. When I'm going back to my recipe, I understand everything.

Superfats: Shea butter and Avocado oil (2%) and (6%)

At trace: Honey

Essential oils: None

Colour: Turmeric powder for the red/brown and natural yellow (Shea butter and honey)

Saponified oils: Shea butter, coco, olive, sunflower (20%)

I had a high amount of sunflower oil, first of all and I had also less saturated fat than unsaturated: 42/58.

The honey in the soap maybe is part responsible of the rancidity of the soap, for this one I have no idea. 

The soap doesn't smell anything in particular, just the soap as normal
I used mineral water for this soap because I was run out of distilled water and I wanted to notice the difference about the lather.

Another point as well, I kept my curing box into my room rather than to let it in a ventilated place, this doesn't help.

The general iodine value of this soap is 67, the suggested range on Soapcalc is between 41 and 70.

So after 7 months, that's the result, already some orange spots. I'm gonna use this one for my laundry, no waste.