How to create DOS

[Blufuz]

Hello! I have a backwards request: could anyone give advice on a sure-fire way to induce DOS in soap? Specifically with something you could put the soap in contact with, or maybe an environment. Preferably something you can easily control as well.

I am testing different additives (like salt, citric acid, jojoba oil, etc) to see which are really protective against DOS, and I would like to stress-test the final soap to see if the ingredient helps.

I don’t want to actually change the soap recipe for the test though (like higher superfat or tap water).
In Kevin Dunn’s book he uses some fancy colormeter which I don’t have, so I’m hoping for things around the house that accelerate the process.

I read that copper can increase DOS, so I thought maybe sticking a penny on the soap might work? Or does leaving the soap in sunlight make a difference?

Thanks for your help!

 

[user 29214]

Leaving it in the sunlight will make a difference.

 

[AliOop]

The copper penny would probably do it, as well.

 

[Marsi]

copper doesn't always trigger dos in solid form (but it can in water, like water from a copper hot water pipe)

I would try something like a crome shelf (the gridelines of dos are really obvious) or rusty iron.
A kitchen window is a good place to trigger DOS (never thought I would say that ) - UV/sunlight and moisture is a classic risk combination.

So .. a rusty metal soap holder on a kitchen window with a copper penny on top ...

 

[Blufuz]

So I’m going with the copper penny at the moment because it’s a cloudy month ahead, but so far, the penny in the (white) soap containing a lot of salt started sweating blue liquid??? Chemistry is weird…

 

[dmcgee5034]

So I’m going with the copper penny at the moment because it’s a cloudy month ahead, but so far, the penny in the (white) soap containing a lot of salt started sweating blue liquid??? Chemistry is weird…

That sounds photo worthy….. now I’m curious….

 

[Blufuz]

That sounds photo worthy….. now I’m curious….

Day 3:

 

[Blufuz]

base recipe:
100g sunflower oil
13.2g NaOH (3-4% superfat)
30g distilled water

Additives test:
1. 5g beeswax
2. 10g salt
3. 5g jojoba oil
4. Nothing
5. 3g baking soda
6. 2g citric acid (+1.2g more lye)
7. 10g sugar

Order in the picture:
1 - 7 - 2
3 - 4
5 - 6


“Research goal”: can a mediocre single oil soap be made much better with easily available additives

Question 1: can some additives reduce the chance of DOS?
Question 2: can other additives just make the soap “nicer”?

 

[Blufuz]

Results so far:
- beeswax took 3 days to become hard enough to unmold, maybe too little lye
- way too much sugar, made the soap extremely crumbly

 

[DeeAnna]

Actually, metallic copper is a very effective trigger for rancidity in soap and fat. In a study done in the early 1900s (I'm away from my soap articles or I'd look it up), the researchers put fats in containers made of various plain metals to see which one(s) induced the fat to go rancid. Copper was clearly a winner of this contest.

To corroborate this, an SMF member @topofmurrayhill made a tool from brass (an alloy of copper) for their soap making. Some weeks after TOMH used the tool on their soap bars, the soap had become rancid where the soap had touched the brass. The thread where TOMH talks about this is here -- Interesting demo of metal causing DOS -- although the photo they shared is no longer available. Wish it was -- the rancidity caused by the brass was unmistakable.

A related thread where SMF member @TeresaT talks about using a brass stamp to decorate soap -- Brass Soap Stamp

 

[Marsi]

@Blufuz - that blue will turn green and eventually an orange brown (not specifically DOS, but a very similar colour, perhaps slightly more dirty brown than orange, but with an orange hue).

I've found the same with brass - most brass will trigger dos rapidly.

 

[lucycat]

Leaving it in the sunlight will make a difference.

Agree; almost guarenteed if it is setting in full sun for a few days. Just give it time after that.

 

[lucycat]

Over the years I have had some soap that sweats when it cures (all lard was my worst). If it is sweating with moisture as it cures it seemed to always be a dos problem after a year or so.

I hope your test is for quite a bit of time. The biggest problem with DOS is that on my soaps it might take 2 years to show and then I am not able to really decide whether that soap was in the sun more or I didn't store properly. I wouldn't expect DOS earlier than 4 months with your penny test (a guess) but it could take much longer.

 

[Blufuz]

Over the years I have had some soap that sweats when it cures (all lard was my worst). If it is sweating with moisture as it cures it seemed to always be a dos problem after a year or so.

I hope your test is for quite a bit of time. The biggest problem with DOS is that on my soaps it might take 2 years to show and then I am not able to really decide whether that soap was in the sun more or I didn't store properly. I wouldn't expect DOS earlier than 4 months with your penny test (a guess) but it could take much longer.

Good to know! The idea with the sun and penny was of “accelerated lifetime assessment” which they use in tech to see how long a gadget could theoretically last by putting it in harsh environments. So I’ll keep the soaps outside for the next 4 months; if I don’t see DOS by then I’ll leave it all in the cellar indefinitely.

 

[Becky1024]

Good to know! The idea with the sun and penny was of “accelerated lifetime assessment” which they use in tech to see how long a gadget could theoretically last by putting it in harsh environments. So I’ll keep the soaps outside for the next 4 months; if I don’t see DOS by then I’ll leave it all in the cellar indefinitely.

I’m interested to see your results! Years ago I also did a DOS study because I thought a bottle of essential oil was causing DOS. Part of the study was to expose half of the bars to sunlight. The only bar that ever showed DOS was the unscented one left in the dark.

 

[ToniO]

Wow! I never knew about copper causing this but it absolutely explains why one log of a batch of GM soaps got funky yellow edges! I beveled them using a piece of flat copper that I had put an edge on! Dang! I was stumped as to why only one log was acting that way when all the others were fine but never thought about the copper!
Good to know!!

 

[Blufuz]

I’m interested to see your results! Years ago I also did a DOS study because I thought a bottle of essential oil was causing DOS. Part of the study was to expose half of the bars to sunlight. The only bar that ever showed DOS was the unscented one left in the dark.

Maybe I should first do a test for the best DOS cause before testing for the best DOS cure

 

[Savage Daughter]

copper doesn't always trigger dos in solid form (but it can in water, like water from a copper hot water pipe)

I would try something like a crome shelf (the gridelines of dos are really obvious) or rusty iron.
A kitchen window is a good place to trigger DOS (never thought I would say that ) - UV/sunlight and moisture is a classic risk combination.

So .. a rusty metal soap holder on a kitchen window with a copper penny on top ...

I have all my soaps curing on chromed, horizontal grid-type shelves & have not noticed this as of yet.

 

[AliOop]

I have all my soaps curing on chromed, horizontal grid-type shelves & have not noticed this as of yet.

Could it be that your shelves actually have a stainless coating? If so, that would not be a problem as long as the coating remains very intact. Unfortunately, I learned the hard way that such coatings will develop cracks or flakes over time (especially with exposure to the high-alkaline nature of fresh soap), and eventually DOS will result. I now line the shelves with baking paper that lasts quite a long time before it has to be replaced. Others use silicone mats or plastic embroidery mesh that can be rinsed clean and almost indefinitely.

 

[Blufuz]

I can confirm that pennies create instant DOS:

Maybe it’s hard to see from the photo, but there’s a brown rim around each coin on the soap, some bigger than others. I don’t actually know if it’s the normal DOS, but stains have also formed on the outside of the “eggs”. No stains are present on the matching soaps left in the dark dry cellar on baking paper, so something is happening.

So far:
- salt is the worst off, with the blue-green discoloration turning brown at the edges, and spread furthest
- sugar may be the best off but I must have added way to much because after a month it’s still squishy/crumbly so almost not soap
- the others are all similarly “stained” by 1-2 mm around the penny and light patches on the body, including the control with nothing in it

Maybe in another month the differences will be more pronounced.