DOS on only a few bars

[Soapin]

Hello.

I make batches of 50 bars. I would say out of the 50 bars, less than 5 bars end up with a single small orange spot that does not spread to the rest of the bar. I’ve got bars of soap that are a year and a half old that have never developed DOS. I use distilled water, olive oil, coconut oil, shea butter, and castor oil. I cure them on coated metal cooling racks in a not-so-well-ventilated place (I know I need to change that.) I superfat at 4% before adding the lye water. One thought I had is how I mix my oils. Essentially, I don’t mix my oils. I put them in a pot, melt them down, and then I mix in the lye water. I was wondering if maybe there’s a higher concentration of certain oils in some bars because I didn’t pre-mix my oils. Is it advised to stick-blend your oils before mixing in the lye water?

Also, with only 10% or less of my bars showing a single spot, is this normal? Even if you do everything right, will you still see an orange spot occasionally?

Thank you for reading this, and I’d appreciate any thoughts!

Steven.

 

[osso]

I believe metals in your tools (pots, spoons, racks, etc), unless stainless, can contribute to DOS. How is your ambient humidity? That has been the biggest factor in my experience (given that the oils used are stable and fresh).

 

[dibbles]

I cure my soap on a cooling rack (which was previously used in my kitchen). I noticed the same thing - one bar with a single DOS, never spreading, on a couple of batches. Once I figured out the baking rack might be the cause, I went to a craft store and bought a sheet of plastic canvas used for embroidery and layed it on top of the rack and haven't had a problem since:

http://www.joann.com/plastic-canvas-7-count-12inx18in/1419571.html#q=plastic+canvas&start=2

 

[DeeAnna]

I am pretty well convinced that single isolated spots of DOS are created by some small bit of an impurity -- probably a microscopic flake of metal.

We can do everything we can as soapers to avoid adding metal contamination when making soap and curing it out -- I'm all for doing that! Unfortunately the oils and other ingredients we use in soap come to us with traces of metallic impurities from the equipment used for processing.

The only realistic way I know of to deal with this unavoidable contamination is to include a chelator in my soap batches. Sodium citrate and tetrasodium EDTA are the two most common ones. A chelator (aka chelant) is a special type of chemical that is able to bind to metal atoms and prevent these metals from catalyzing the oxidation process that makes DOS.

 

[Soapin]

Thank you, everyone! Here are some responses:

1) That's a great thought about the metals my tools are made of. I use only stainless steel, but then it occurred to me that I use a guitar string cutter, and I don't know what the strings are made of. Steel, I'm sure, but stainless? I don't know. Is there a certain material our strings should be made of?

2) I definitely want to check the humidity. I will do that!

3) I'm getting ready to remove about 250 bars from my cooling/curing racks tonight (or at this rate, maybe tomorrow night). I want to see if any of them have DOS. If they don't, I'll watch them to see if it's happening after I box them.

4) That thing about impurities is disappointing, but I bet it's at least a little bit true! You just can't expect good quality in anything these days!

Thanks again for all your thoughts. You all are always so helpful!

 

[DeeAnna]

I use a guitar string cutter and yes, it's some type of hardened steel but I don't think it is stainless. We really don't have much choice in the matter -- if you want a wire cutter, you need the strength and resiliency of a guitar string or piano wire. I suppose there is a chance of a tiny bit of metal flaking off onto the soap from the wire, but frankly, there comes a point of diminishing returns where it makes no sense to me to obsess over these tiny risks, unless obsessions are a person's idea of fun entertainment.

DOS usually takes time to appear. If you are seeing what you think is DOS develop within the month or so while the soap is curing, it could be DOS, but it is as or more likely to be some other issue.

Tiny amounts of metal impurities in our ingredients isn't an issue of "good quality" or bad. It is just a fact of living in the natural world. If you don't want metallic contamination, then you are essentially asking the world to harvest thousands of acres of oil-bearing crops grown on soil that doesn't contain any metals and using agricultural equipment and processing methods that do not use metal.

 

[Susie]

If you are only getting DOS on 5 or less bars per 50 bar batch, your humidity is not the issue.

 

[Stacy]

I play(ed) guitar for a while but never really thought about the makeup of the strings beyond nylon vs metal.

From what I've found, you can get Stainless Steel strings, but there are other metals as well.

Stainless steel strings are best suited to playing true rock. Their sound is bright and capable of sustaining. They are louder than other string options, but the purity of their tone production is short lived. Stainless steel strings are rough and tend to produce a high level of noise along the finger and the fret.

You can go to any music store and ask for them specifically. Some stores sell single strings, but you may have to buy a package of 6 (enough to restring a guitar) and not all the strings will be fine enough to use in a cutter. Price depends on the brand, but when I was buying them, I could get a set for 10-15 dollars.

 

[Soapin]

Thanks again, everyone! Deanna, I see what you're saying now. Traces of metal in our oils might just be a natural result of the metal equipment used to process the oil. Noting you can do about that!

Thank you, Susie. That makes sense to me, too: if it was humidity, it would affect all the bars. Still, I think I'll try to find a way to increase airflow over the bars. Wouldn't hurt!

Stacy, that's a good tip. Thank you! I will look for stainless steel strings. It might not help, but ya never know!

On one hand, it's only 5 bars out of 50, but then again, my concern is that I can't see these bars once I package them up for sale. I don't want to package them, sell them, and then have one open a bar to find an orange spot. I might not be able to stop the spots completely, but I intend to try!

Thanks again, everyone!