# Cleaner Processes for Making Laundry Soap from Vegetable Oils and an Essential Oil
## 3 Results and Discussion
### Confirmation of the Presence of Essential Oil in Soap
#### 3.2.5 Thermal Analyses: Thermogravimetric Analysis (TGA) and Differential Thermal Analysis (DTA)  
Analysis DTA (Figures S3 and S4) highlighted that the successive stages of the soap sample burning profiles are as follows: evaporation of moisture, volatile release, burning of the volatile compound in evaporation of moisture, volatile release/char formation, burning of the volatile hydrocarbon in the gaseous space, and combustion.  
At the end of the thermal analysis, the higher values of the mass difference compared to the standards (without essential oil) formulated hot or cold are the results of the burning of the soaps but also of the volatilization/burning of the essential oils in the soaps (Table 4).  
Figure 6: Elemental mapping for cold-formulated (CS1–CS4) soaps.  
Although hot saponification is more efficient, proceeding with a higher yield, after the burning of the soap a lower mass loss is still recorded compared to the case of the cold-formulated soaps. Cold saponification preserves the essential oil in larger quantities, which it eliminates during the burning of the soaps, leading to losses of up to 12.64 mg in the case of the soap containing Neem (Figure S4b).  
The flash points of essential oils are lower than 100 \({}^{\circ}\)C: 55 \({}^{\circ}\)C for Thyme, 56.6-59 \({}^{\circ}\)C for Tea Tree and 76 \({}^{\circ}\)C for Neem, which is why they must be added after the completion of the hot saponification process to avoid their destruction. If the mass loss in the range 40-100 \({}^{\circ}\)C is analyzed (Figures S3 and S4), it is found that soaps containing essential oils record a greater mass loss (by 0.1-0.6 mg/50 mg soap) than the standard soaps, formulated hot/cold.  
The temperature during the saponification and the duration of mixing the soap mass with the essential oil are two factors that must be taken into account. It can be said that the cold saponification method is preferable to the hot one because the low saponification temperature eliminates the risk of release of volatile compounds (such as terpene and aldehydes) from the essential oil used in soap formulation, thus maintaining, in the long term, both perfume and other properties induced to the soap.  
It turns out that the main advantages and disadvantages of each soap formulation process, in terms of the effectiveness and properties of the soap that includes an essential oil, are the following [(39; 62)]:  
1. _In the case of cold saponification_: Ease of application, better control of the components in the recipe, no alteration in the quality of the base oils, and better preservation of the properties of the essential oils due to the preservation of compounds susceptible to volatilization because the processing temperature during saponification is low. As regards disadvantages: long ripening time (at least one month) and the risk of degradation of the base oils and essential oil during the ripening period, due to different storage conditions (air, humidity, heat, oxygen).
2. _In the case of hot saponification_, a ripening stage is no longer necessary, resulting in faster soap production. However, part of the volatile components of the essential oil evaporates even if their addition is made at the end of saponification, as the volatilization process cannot be controlled.
3. _In both saponification processes (hot/cold)_, glycerin is also a result of the reaction by-product, which, by not being removed, gives laundry soap the ability to improve the feel of washed laundry (as a fabric softener) and reduce electrostatic charge in textiles.