Khotso Manufacturing Melt and Pour Soaps

The Khotso soap base is an extremely easy to use product. With this you can make soap bars of almost any colour, which can be fragranced to your requirements and can even incorporate novelty items.

Some basic procedures:

Finished soap bars are made by melting the Soap Base and pouring the melted soap into moulds. The soap bar will always be of good quality if this procedure is followed.

1. Molds.

The molds must be clean and manufactured from suitable materials. Moulds made from any plastic material (including silicone) are suitable but it should be noted that moulds made from iron, copper or brass may sometimes discolour the soap bar.

2. Melting the soap base.

The soap base must be heated in a suitable container to melt it. Glass and Stainless Steel containers are ideal whereas iron, brass or copper may add to discolouration of the soap. Heating must be done carefully to avoid overheating the melt and pour soap. If the soap base is overheated it may become dark in colour in addition it is often the cause of ‘sweating’.  If the soap is being heated by an electric element or by gas flame it must be continuously stirred to avoid overheating, indirect heating is the preferred option.

3. Correct pouring temperature and pouring technique.

The M&P soap base should be completely molten and taken to a temperature between 65 and 75 °C  It should be slowly stirred whilst warming to keep the temperature in the container uniform. When the temperature is between 65 and 75 °C. stirring should be stopped to allow air bubbles to rise out of the soap. Best results will be obtained if the soap is run into moulds from the bottom of the container used for melting the M&P soap base. If the soap is poured from the top of the container, it should be poured slowly to avoid getting air bubbles in the block of soap. The molded soap bars should be handled carefully until they are completely cool. (typically below 30 °C)

4. Removal from the mould. packing and storing.

The soap bar will release from the mould more easily if it has been left for 24 hours in a cool place. When the soap bar has been removed from the mould it should be wrapped immediately in clear film to retain an attractive appearance. The soap should be ideally stored at temperatures not below 5 C and not above 30 °C.


 Fragrancing soap bars.

1. Understanding fragrances.

Perfumes are complex mixtures of organic substances. A perfume contains many substances with individual odours and it is the mixture of these odours which gives a fragrance its unique individual smell. Other substances are added to cosmetic fragrances and some examples are:

  • Diluent: added to improve the solubility of the perfume. (see encyclopedia)
  • Fixative: added to reduce the volatility of the odour producing chemicals and make the perfume odour last longer. (see encyclopedia)

2. Correct choice of perfume.

Trials in our laboratories have shown that most perfumes can be used successfully in the soap base. However some points should be noted. Fragrance & essential oil manufacturers produce different blends of fragrances for different applications. A fragrance for use in scented oils or candles will contain a wax or oil soluble diluent which may cause problems if it is used in water or soap based products. Some fragrance oils are sold as ingredients for Fine perfumes and contain high levels of fixative. The fixative may be waxy in composition and this too can cause problems in soap based products.

When asking perfume manufacturers to supply fragrances you should always ask for product suitable for incorporation into soap bars. Before using your fragrance in full scale production, you should carry out compatibility trials

3. Conducting compatibility trials.

Perfumes should be ideally checked for:

    • ease and completeness of solubility
    • stability in the soap bar at low temperature
    • colour in the soap bar
    • compatibility with the bar wrapper.

The concentration of perfume used in the soap bar will determine the odour level of the bar. High concentrations of perfume will give a bar with a strong perfume smell but may cause problems with colour, clarity at low temperature and deterioration of the wrapping. Perfume concentrations of 1 % or less usually give an acceptable odour and rarely cause stability problems. Levels of 2% or more may affect colour, may cause wrapping film to deteriorate quickly and at times have been shown to affect clarity of soap bars at low temperature. To carry out a compatibility trial with perfume / fragrance  proceed as follows:

    • Take enough weight of soap base to fill 2 small molds
    • Carefully heat the soap base to 65+ degrees C. and ensure it has molten completely.
    • When the molten soap has cooled to 65 degrees C add 1 % of the perfume being evaluated and stir until completely dissolved.
    • Pour equal amounts of the perfumed soap into each of two moulds and check that the soap is clear and free from air bubbles.
    • Allow to stand overnight, remove from the moulds and wrap the bars tightly in shrink film.
    • Label the bars with the perfume name or reference number and the words” 1 % concentration.”
    • Repeat the above procedure using 1.5% of perfume and 2% of perfume and label the bars with the perfume name or reference number and the percentage used.
    • Make 2 more bars in the same way but do not add perfume. (these bars are called reference bars and are used to make comparisons)
    • Store one of each perfumed bar and one reference bar in a refrigerator at about 4 degrees C. Do not store in a freezer!
    • Store the other bars at room temperature.

Compare the appearance of the test samples with the reference samples daily. At the end of day 7 the trial is complete. If the bar containing 2% perfume stored in the refrigerator is clear and the bar stored at room temperature is clear and not discoloured then the perfume is satisfactory for use at 2%. If the bar containing 2% perfume is cloudy but the bar containing 1.5% perfume is clear and not discoloured then the perfume is satisfactory for use up to 1.5% concentration and so on. In this way the maximum concentration of any perfume giving a transparent bar can be found.

With some fragrances the bars will remain transparent but may be slightly discoloured compared with the reference sample. If the bars are going to be coloured with dyes or if discolouration is slight the fragrance oil may still be acceptable.

Next, the shrink wrap should be examined. Take the bars that yiou had stored at room temperature and compare the appearance and feel of the shrink wrap on the perfumed bars with that on the reference bar. Note any wrinkling, staining or loss of strength of the film. By doing this, more information is obtained as to the suitability of the perfume.


 Colouring soap bars.

Soap bars can be made in almost any colour by adding dispersions or dyes. It is important to ensure that only colours which are approved for skin contact products in the country where the soap bars are to be sold are used. See our colour offers for help to choose suitable colours.

1. Adding colours to soaps

Colours can be supplied as liquids or powders. Very small amounts of powder dyes will give very intense colours and if powder dyes are added directly to melted soap it will be extremely difficult to judge the correct amount to add. When added directly powder dyes are often slow to dissolve so “pockets” of dye powder can remain in the soap bar. Then when the bar is used the dye powder will dissolve in the wash water giving intense colour which could stain skin and sanitary ware.

To avoid problems use the following procedure:

  • First dissolve the dye powder completely in water. A 10% solution of the dye is usually best to work with (100 grams of dye in 1 litre of warm water) for batches of soap of 100 kilos or more. For smaller batches a 1% solution (10 grams of dye in 1 litre of warm water) is better. Make sure the dye is completely dissolved before using .
  • As a guide, between 0.001% and 0.01% of a 10% dye solution (large batches 1ml to 10 ml of 10% dye solution per 100 kilos of melted soap, small batches 1ml to 10 ml of 1 % dye solution per 10 kilos of melted soap) will give a good colour ranging from pastel to intense. When the soap base is completely melted add the dye solution slowly with continuous mixing. If perfume is to be added as well as colour then it is suggested that the fragrance and colour should be added together. When the colour is uniformly mixed the perfume will also be uniformly mixed.

2. Checking colour stability.

Some colours are fugitive, that is they fade on exposure to light. Some colours may react chemically with compounds in perfumes. Because of this it is wise to check for colour stability of the soap bar. To do this simply store one bar in the dark in a refrigerator, one bar in a room away from direct daylight and one bar near a north facing window. (Nearly all colours will fade in direct sunlight.)