I noticed that some initiatives of reusing used oil with the production of soap, both individual entrepreneurship as NGOs, using calcium carbonate or dolomite – ore of calcium carbonate and magnesium.
I was curious because the addition of such charges levied on the product costs and only justified if it had a very specific function. Ask information and how no one answered, I decided to do some tests.
The formula used was this. The water based dye blue dye was used for better visualization of the test. To measure the difference in hardness of the soap was improvised device this mimics an apparatus for measuring impact. Consists of a driver tube, 1 meter high which is released by a steel rod with 15g weight. Gravity this rod goes through the driver tube and penetrates into soap. The hardness is measured by penetration depth (mm).
The soap was drying for 25 days before hardness test and both with and without carbonate, had the same hardness value of 6 mm.
The foaming test was done with a shaving brush rubbed in a standard way to develop the soap foam. Not noticed any difference. The behavior of the wet soap was also identical, forming the “gooey” feature of this type of soap.
To test the oxidation (rancidity) of soap, they were left next to a glass window exposed to direct sun in the morning for 10 days.
Significant difference, the soap with calcium carbonate has much better oxidation resistance.
From what has been tested we can only say that calcium carbonate improves the oxidation resistance of this type of soap that is very prone to rancificar. I believe that this is not the main reason to use dolomite or calcium carbonate used in oil soap, but unfortunately was unable to have more elements that could justify its use. I also regret that the people who use this kind of load does not divulgem the merits of doing this, so that the costs justify the penalty, everyone would gain.