Hot Process Continuous Stirring – HPCS


In the small town of Fontevraud L’Abbaye in the Loire Valley in France, since 1974 there is a renowned handmade soapmaker, Savonnerie Martin de Candre. Since its founding 40 years, Martin de Candre soap manufacture (MdC) is dedicated to producing excellent quality handmade soap products, as they say, using the classic process of Marseilles soap.

The soap (cream) shaving of Martin de Candre is considered the best in the world, they have a line of Marseille soap (for cleaning) with olive, coconut and palm, a line call huile de palme that is made with olive , coconut and palm oil and a third, huile d’olive, only with olive and coconut.

All these products have a premium price ranging 9 to 16 euros for soaps bars and shaving soap can cost 23 euros one container of 50 grams.

They claim that make the process of Marseilles soap which is a full boiling process where the soap is rinsed with salted water and glycerin is removed. In reality MdC makes a fairly conventional handmade hot process, which uses a mechanical stirrer to stir the mass during saponification and the lot size is less than 25 kg. This can be seen in the few photos on their website and also a video report produced by a French TV.

But what caught my attention was the procedure them to dry for eight months the soap bars and for 5 months the shaving soap! Intriguing because the hot process soap has saponified out and therefore safe and drying 15 days is enough to have the necessary hardness for lasting use. A soap made by Cold Process is ready for use in about 20 days. Here comes the question, why make a process more complex, lengthy and expensive process that is hot, if I can make cold process much simpler, faster and cheaper? After leaving it for 8 months a soap made ​​by hot or cold, theoretically they would have the same performance. It is clear that the hot process has the advantage of being able to incorporate sensitive components after alkaline saponification, which preserves these components, in which process cold is not possible.

I decided to design a test to compare the properties of a soap made by cold process and the same made by hot process and also compare the influence it has drying time in soap performance in both cases.

Hot Process with Continuous Stirring – HPCS

A handmade hot processs is normally done using as source of heating a double boiler or an electric slow cooker (crock pot), and the mass is homogenized manually from time to time to enable a comprehensive saponification.

To keep the process more akin to the Martin de Candre hot process, I designed a system called Hot Process Continuous Stirring – HPCS. Obviously not is an innovation, but in the artisanal scale not seen anyone use a similar system.
Thus, a comparative test between soaps produced by two distinct processes, eventually drifting to the development of a third way to do a hot process that is the HPCS.


This is the setup of the equipment to do the HPCS – an electric heater (this is a laboratory magnetic stirrer), a mechanical stirrer (used with digital speed control) and a digital thermometer.

Here’s a video I made showing the HPCS to make benzoim soap (12 minutes):

Soaps Testing

The Martin Candre in your palm line has a honey soap and a benzoim (tonkinense Styrax) soap, and were made simlilar these for testing. The oil soap composition was: olive / palm kernel / palm – 60/25/15, SF 5% and lye concentration of 30%. The comparative test will be done with the honey and the benzoim was done to confirm and optimize the process HPCS. You can not make a regular cold process with benzoim because of the need to dilute the benzoim oil resin with ethanol, which would give the defect of seizing on mass.


On the left the soap made ​​with honey HPCS, the other by conventional cold process. The color is dark in the cold process due to carbonization of the sugar honey by lye.


The two blocks of honey soaps , 3.5kg.


Cut surface finish of the honey soap by hot process with continuous stirring using Flex Cutter.

P1030344Two bars 305 x 80 mmm

P1030351Finishing the top of bars


The two bars finished in the dimensions of 305 x 80 x 60 mm.


Cutting individual bars using Flex Cutter.


Cut with precision Cutter Flex.


All individual bars 80x60x30 mm, 135 grams.


Cut the block of honey soap made ​​with cold process.


All bars of honey soap CP, 90x60x25 mm, 130 grams.


The two soaps will be used in the comparison between CP and HP.

Benzoim soap made by Hot Process Continuous Stirring – HPCS


This soap was made to confirm and improve the HPAC process.


Savonnerie Martin de Candre:

Sulfur soap – a trial

For many years the sulfur containing soap is recognized as effective in treating a variety of skin conditions, particularly in the reduction of acne. Here in Brazil the best known brand is the Granado, Confiânça in Portugal and Dr. Kauffman in the USA.

Usually offered with two doses of sulfur, typically 10% and 4% and with addition of salicylic acid. Has testimonials from people with very oily skin that usually take daily bath with 10% sulfur. The recommendation for the treatment of severe acne is to develop foam and pass that foam in the affected area and leave for a few minutes.

I decided to try to make this type of product in soap manufacture craft. In research that I did not find nothing anywhere that had a reference of how to make sulfur soap in the handmade scope. I imagine that the commercial products is a basic mass of soap is added sulfur and normal extrusion.

One caveat, as the post title says, this is a trial and did so many points are still in the realm of experience and are not fully understood. If you want to duplicate, is at your own risk.

Cold Process

I opted for the cold start process using the two doses of sulfur, 4 and 10%.The first question, how to add sulfur. Two modes, or mix in oils or add the trace. The sulfur is absolutely insoluble in water and an aggravation, or even can be dispersed in water simply do not mix and do not wetted by water, it is always supernatant. It is also not soluble in oils, it is more tolerant of wettability, but not dispersed well in oils.I chose to add the trace because it is already difficult to disperse in oils, imagine mixing the mass swelling in the trace.

After 24 hours, the time of demolding, the soap with 4% sulfur was completely soft it was not possible to handle and had to wait 48 hours, but even so the soap was still soft and so remained until the end of 20 days. At first I could not understand what happened in this soap that was too soft and greasy, a sign that not all oils saponification.The soap was 10% normal with a reasonable hardness and it was then possible to cut.


This soap with 10% sulfur as drying  began to develop marks on the surface of the soap. These patches is sulfur powder that had migrated to the surface of the soap.

These stains can be removed with scraping and they have no tendency to return.

This soap with 10% sulfur, made by cold process has good characteristic has hardness makes a good foam and cleansing property is extremely high, very suitable for oily skin, typical of a sulfur soap.

The soap containing 4% sulfur remains soft after 20 days and formed an interesting is that the outer layer and the inner yellowish acquired a very dark brown color. This layer of yellowish oil that is probably not saponificated. This may be due to lack of lye that may have been consumed in some interaction with sulfur, as strange as it may seem. This soap did not work and will be discarded

click here to download formula

Hot Process

I changed the formulation to save the expensive oils and did a simple formula by removing the avocado oil and shea butter and increasing olive and castor oils. The process used was a conventional hot process using the slow-cooker (crock pot). The phase translucent gel was obtained within 2 hours of cooking. Divide the dough, a part in a water bath and the other remained in the slow-cooker. This water bath was added 10% sulfur and other 4%.

In both cases it was very difficult to incorporate the sulfur into the bulk of the hot process. Form is difficult to disperse clumps, even adding more hot water to the dough.

This 4% sulfur was added into the mixture remained in the pan at the bottom of the pan where the temperature is higher, the sulfur melted and formed dark brown lumps, typical of molten sulfur. Sulfur has a melting point around 112 ° C and forms a high viscosity liquid and dark brown. The white dots are mass with soap has not been mixed with the sulfur.

The two sulfur soap by hot process has good properties in general despite not looking very uniform due to the mass of white dots not mixed with sulfur and dark spots due to the fusion of sulfur.

click here to download formula


Comparing the color of the soap made with both methods it is possible to infer that there is an interaction between the soda and sulfur in cold process. The dark color is the result of this interaction, which does not occur in hot saponification process as already occurred when adding the sulfur and the color remained the natural color of the soap somewhat lighter due to the inherent color of sulfur. Soap 4% by hot process color is darker compared to 10% for the same procedure there was little fusion sulfur dyed a little soap.

This interaction of sulfur with lye is only possible if there is a reductor agent which enhances the reaction of soda with liquid sulfur. There may be a penalty in the blend of oils that enables this reaction. It is only a hypothesis that lacks a proof.

The greatest difficulty is the incorporation of sulfur into the soap mass so that it is smooth. As the solubility of the sulfur and the dispersion is zero in both water and oils and very difficult to obtain good mixing. The aggravating factor is that sulfur has a strong tendency to form lumps difficult to disperse. A method for screening to minimize the sulfur is in a fine mesh before entering added slowly and stirring the process allows. Another difficulty is the melting of the sulfur that generates a viscous dark brown to eventually contaminate the soap when done by hot process temperature to rise too much. The soap containing 4% sulfur by cold process needs to be repeated to determine the cause softening and excess oils without saponification. I may have made an error that eludes me to perception, it is very strange happened that made me drop the soap. Also pending is the effectiveness of this handmade soap sulfur with respect to the treatment of acne because it was not possible until now to do the tests.