Soap Making Production
AN INTRODUCTION TO THE SMALL SCALE MANUFACTURE OF TOILET SOAPS
CONTENTS
(1) INTRODUCTION
(2) PROCESSES
(3) EQUIPMENT
(4) EQUIPMENT SELECTION
(5) BASIC MATERIALS
(6) PLANT LAYOUT
(7) MANUFACTURING OPERATIONS
(8) TESTING
(1) INTRODUCTION
This manual is intended for those with little or no experience of soap manufacture to select equipment and materials to produce soap
tablets to a basic formulation. The process described refers to what are called soap finishing operations. They are the physical actions
performed on soap bases to transform them into soap tablets. The processes by which soap bases are formed by chemical reaction
(saponification) are not included here. The manual only relates to SUNLAB machines and equipment.
(2) PROCESSES
Soap bases for the finishing operations are generally purchased in the form of noodles or chips. The colour, fragrance and other
ingredients are added and mechanically mixed so that they are evenly distributed throughout the base.
To produce a homogenous material the soap mix is subjected to heavy mechanical working by means of a triple roll mill or a refining
plodder. This not only intimately mixes the base and additives but also refines and to some degree physically modifies the soap structure.
The machines produce either compacted ribbons or noodles of soap which are then compressed and extruded in continuous bar form by
a plodder. The extrusion is cut into lengths by a soap cutter and finally stamped in a press fitted with a mould to give the desired shape
and weight.
The soap finishing processes may be summed up as:-
OPERATION MACHINE
Weighing of additives Digital scales
Rough mixing Paddle type mixer
Homogenous mixing/refining Triple roll mill or refining plodder
Compressing and extruding Extruding plodder
Cutting to length Cutter
Forming to shape Stamper fitted with a mould
(3) EQUIPMENT
(3.1) MIXER – Generally described as a tilting type paddle mixer, its function is to coat each noodle with a small amount of the additives
thus ensuring even distribution throughout the mix. It is suitable for processing up to 6% of liquid additives to the soap base.
(3.2) MILL – Our mills are equipped with three rollers each rotating at different speeds so that the soap passing through them is subject
to a grinding and tearing action modifying the physical structure and mixing the base and additives thoroughly. The working of the soap
is beneficial to the lathering characteristics and can give a slightly harder soap with fewer tendencies to absorb water.
(3.3) REFINING PLODDER – This machine performs a similar function to the mill but the action is not so severe. It can be used as a
cheaper alternative to a mill although modern production lines generally incorporate a mill as well as a refining plodder.
(3.4) EXTRUDING PLODDER – The millings from the mill or noodles from the refining plodder are compressed under considerable pressure
by the action of the screw (worm) forcing the soap through a warmed conical chamber and then through a die shaped to suit the cross
section of the eventual tablet.
(3.5) CUTTER – The extrusion from the plodder is cut into correct lengths for stamping.
(3.6) SOAP PRESS or STAMPER – The stamper provides the force to form the soap into the shape of the mould.
(3.7) SOAP MOULD or DIE – Determines the shape of the tablet.
(4) EQUIPMENT SELECTION
(4.1) MIXER – Two sizes are available; the 7.5M to mix 7.5kgs batches and the 25M to mix 25kgs batches. To mix a charge thoroughly
takes about 5mins, allowing for charging and discharging one mix could be achieved every 10mins.
(4.2) MILL – Three sizes are available; M75 (75mm diameter rolls giving 30kgs per hour), M100 (100mm diameter rolls giving 90kgs
per hour) and M150 (150mm diameter roll giving 180kgs per hour). Mills are fitted with hardened stainless steel rolls and can also be
fitted with water-cooling and temperature sensing.
(4.3) REFINING PLODDERS – These come in three sizes (measured by nominal inside barrel diameter), 100mm – P100, 125mm – P125
and 150mm – P150. They can be supplied with a variable speed motor which can be an advantage if a range of soap bases are to be
processed. The output of noodle soap is respectively 100, 130 and 180kgs/hr.
(4.4) EXTRUDING PLODDERS – These come in the same range of sizes as the refining plodders. It is a definite advantage to have a
variable speed facility for the extruding operation. Both to influence the finished appearance of the extruded soap and to control the
rate of production. Output of extruded soap will be approximately the same as the refining plodders.
Extruding plodders can be provided with refining/noodling heads which can be inter-changed with the extruding head so that only
a single plodder is required for the two operations. Obviously the output will be reduced inversely by the number passes of the soap
through the machine.
(4.5) EXTRUDING VACUUM PLODDERS – A vacuum facility can be provided for the three sizes of extruding plodders.
This is achieved by reinforcing and enclosing the hopper. It is useful if soft mixes or translucent bases are to be processed.
The disadvantage is that the machine has to be stopped and the hopper recharged.
(4.5) SOAP CUTTERS – For cutting the soap extrusion into predetermined lengths these are available in a variety of designs.
Hand operated cutter HSC, foot operated cutter FSC, semi-automatic pneumatic cutter LMKPC and automatic rotary cutter.
The first three are suitable for cutting extrusions of all shapes and sizes. Selection would normally be determined by the
quantity to be produced. The rotary cutter requires a different cutting head for each significant variation of length to be cut.
It is more suitable for long runs.
(4.6) SOAP PRESS / STAMPER – Two forms of stamper are available; a manually operated model LMK1 which has a maximum soap
bar capacity of 80g and two semi-automatic pneumatic machines Joraco 1030 for soap bars of up to 80g and Joraco 1530 for
soap bars up to 200g. The manual machine has a rate of production of 6 bars per minutes, whilst the pneumatic machines can achieve
in excess of 10 bars per minute.
(4.7) SOAP MOULDS – There are two distinct types of soap mould:-
Capacity mould – in which a billet a little heavier than the final tablet is placed in the mould and the surplus squeezed out, thus
giving a tablet of uniform weight every time. The mould comprises a top and bottom section.
Collar mould – in which the billet is cut to the correct weight and all the soap remains in the mould. This type of mould produces
tablets with straight sides consisting of top and bottom sections which move up and down inside a collar.
Moulds can be engraved on both top and bottom faces, supplied with an easy release surface or with facilities for cooling.
For costing purposes we divide moulds into simple and complex shapes. The former is defined as being capable of being produced
by a form tool moving in two directions (x and y axis). The latter requires movement of the tool in three directions (x, y and z axis)
and is characterised by multi directional curves.
(4.8) SELECTION CONSIDERATIONS - The main considerations may be summarised as follows:
(a) Volume of output.
(b) Size of tablet.
(c) Type of base.
(d) Economic circumstances.
(a) Volume of output – the overriding factor in plant selection is generally the amount of soap required to be produced.
The maximum rate of production from a combination of the above machines would be about 150kgs/hr and the minimum from
a single machine 20kgs/hr.
(b) Size of tablet – the maximum size of tablet from any machine is a factor of the ratio of the barrel diameter to the aperture of
the die plate. The larger diameter of the barrel the larger the aperture can be and therefore the larger the extrusion before there is
insufficient pressure to produce a compact extrusion. The P100 series can produce tablets up 100g, the P125 up to 125g and the P150
up to 150g. Extrusion under vacuum can increase these weights by as much as 20%.
(c) Type of base – in general we do not recommend the use of economy bases particularly if the proposed tablet size is near the
maximum for the machine. The results are likely to be disappointing. If the proposed base is other than a manufactures premium
type or if it is not a tallow/coconut or palm/coconut but is something a little special such as a translucent or syndet then we would
need to make a specific recommendation.
(d) Economic considerations – these considerations will vary from one environment to another we don’t have a set combination of
machines to produce a certain quantity of soap. Selection can be made on the basis of minimal investment where capital is at a
premium or minimal labour costs where employment costs are paramount.
(5) BASIC MATERIALS
(5.1) SOAP BASES – formed by the action of alkali’s of sodium or potassium on fatty acids and neutral oils from animal and vegetable
sources. Typical bases – tallow/coconut, palm/coconut or palm kernel
Ratio % – premium soaps 70/30
Normal 80/20
Minimum 90/10
The quality of a base is important from three major aspects:-
(a) Colour.
(b) Odour.
(c) Performance.
(a) Colour – of the soap base depends primarily on the fats and oils used. For good quality toilet soaps tallow and coconut oils are
bleached using activated earths. Where palm oil is used bleaching is essential. Base colour is important in determining the whiteness
of white soaps and the brightness coloured soaps.
(b) Odour – the base odour of soap depends primarily on the quality of the fats used and on the subsequent processes. For premium
quality soaps deodorising is usually carried out in addition to bleaching and stabilisers are added. Base odour is very significant when
it comes to perfuming the soap and must be taken into consideration by the perfumer.
(a) Performance – the major factor determining lathering performance is the ratio of tallow/coconut or palm/palm kernel. If the
ratio 70/30 is taken as the recommendation for premium soaps then as this moves towards 90/10 there is a noticeable decrease in
performance. Lathering is improved with the increased proportions of coconut but at the expense of noticeably more irritation to the
skin. The addition of 5-10% free fatty acid promotes skin mildness and at the same time the volume and lather performance increase.
There are several ways of increasing the free fatty content. The commonest is the addition of distilled coconut/palm kernel fatty acid
which is liquid at about 20-26 C. Added at the mixing stage. Good quality soap bases will contain a suitable preservative system to
prevent deterioration during storage and shelf life.
(5.2) FRAGRANCES – Soap fragrances need to be specially developed to suit the intended environment. The perfumer has to take into
account the reactive nature of soap and the conditions that it will be subjected to before and during use. Consideration needs to be
given to the following:
(a) chemical composition of the base i.e. free alkali, sodium chloride content, added preservatives etc.
(b) natural odour base.
(c) Physical shape of the tablet. Experiments show that the loss of an aroma chemical is determined by the rate of diffusion through
the soap matrix. Thus at a given time the concentration of aroma chemicals will be less at the surface than at the centre and thicker
sections will retain them longer than thinner ones.
The perfuming soap is a science and an
art and very defiantly the province of the expert. Even acting on the advice of the expert soap fragrances must be product tested by
incorporating them into trails bars and subjecting them to tests to determine colour stability, satisfactory self life, performance in use
and health and safety aspects.
The proportion of fragrance added to toilet soaps ranges from between 0.5 and 2%, with the norm being about 1%.
(5.3) COLOURS – These may be supplied as powders or in liquid form and are specially developed for incorporating into soap bases.
They need to be ineffective by the soap base, fragrances, light and to be stable over long periods.We recommend the use of powders
in SUNLAB mixers as these appear to be distributed more readily and helps to keep the liquid additions to a minimum.
(5.4) TITANIUM DIOXIDE – the prime function of the substance is to whiten the base for white soaps and act as a pacifier and colour
enhance for coloured soaps. The quantity added varies from 0.2 – 0.3% for coloured soaps to 2 or three times as much for white soaps.
(6) PLANT LAYOUT
The machines should be arranged in the sequence of operations i.e. mixer – mill – refining plodder – extruding plodder – cutter – stamper.
There should an area allowed for the storage of soap noodles, a bench for the preparation and weighing of additives, an area for the
temporary storage of tablets and packing area.
(7) MANUFACTURING OPERATIONS
(7.1) WEIGHING OF ADDITIVES – Accurate weighing scales to 0.1g will be needed. Colours particularly powder pigments as they are so
concentrated can be difficult to measure accurately enough to ensure uniformity between batches. One way of ensuring this is to prepare
sufficient for the complete batch or days production and then to bulk it up with one or some of the additives such as titanium dioxide.
The increased bulk can be more accurately weighed for each mixer load. Dilution as a suspension in distilled water or a liquid additive are
other ways.
(7.2) MIXING – the prime object of this mixing operation is to coat each chip or noodle with a small amount of the additives. Dispersal of
the additives is effected by the noodles tumbling and rubbing against each other so one with a high concentration of additives transfers it
to one with a lesser concentration. Over mixing will result in the breakup of the noodles and may lead to concentration of pigment etc
forming. Likewise the addition of too much liquid will cause clogging and inhibit the free movement of the noodles. Larger than
recommended liquid additions can be made in two stages with a refining or milling operation in between.
(7.3) MILLING – Generally two passes through the mill will be needed to give a reasonable distribution of the additives and adequate
physical working of the base, however if there is a refining plodder in the line only one pass should be necessary. The first pass through
mill is liable to be slow because the outside of the will be slippery due to the additives. If there is a refining plodder in the line then it
should be placed before the mill as slippery noodles have no detrimental effect on the performance of the plodder and the resulting
noodles from the plodder will be readily processed by the mill. It is generally beneficial to extrude the mix immediately after milling
while the mass is still warm. However with soft mixes it may be better to allow them to cool a little, so that they become a little harder.
(7.4) REFINING/NOODLING – Used either as a sole means of creating a homogenous mix or in conjunction with the mill. If used as the sole
mixer the soap will need to be passed twice through the machine or two machines will be needed operating in series. The soap mix is fed
into the hopper, either as noodles from the mixer or millings and forced through a fine mesh supported by a plate with a large number of
holes. The soap comes out as macaroni type strings which are cut into short lengths by a rotating multi-blade cutter. The mesh has two
functions to impede the passage of the soap resulting in a smearing action at the end of the worm and a shearing action as it passes through
the screen.
(7.5) EXTRUDING – This is the operation which is the most critical for the soap maker in the sequence of soap finishing operations. The soap
mix is fed into the machine in the form of millings or noodles. The worm forces the mix through first a graining plate which changes the flow
from rotary to linear movement and also creates some back pressure. Then into the compression chamber where it is squeezed and warmed
and finally through the die (extrusion) plate to form a shaped extrusion. Most soap bases are extruded at temperature of between 30/35C.
The greater part of this heat is generated by friction and compression as the soap passes down the barrel and part is added by the heater on
the nose cone, primarily to heat the extrusion plate to impart a smooth finish to the extrusion.
Excessive heat generated in the barrel will lower the friction between the wall of the barrel and the soap thus increasing the tendency for
the soap to rotate with the worm rather than being pushed forward by the worm. The result is a loss of output and possibly a drop in pressure
in the compression chamber. To avoid this condition the barrel is water cooled. In temperature climates mains water at 15/20 C is adequate
for this purpose. In hotter climes a water cooler may have to be incorporated in the water circuit.
CONTENTS
(1) INTRODUCTION
(2) PROCESSES
(3) EQUIPMENT
(4) EQUIPMENT SELECTION
(5) BASIC MATERIALS
(6) PLANT LAYOUT
(7) MANUFACTURING OPERATIONS
(8) TESTING
(1) INTRODUCTION
This manual is intended for those with little or no experience of soap manufacture to select equipment and materials to produce soap
tablets to a basic formulation. The process described refers to what are called soap finishing operations. They are the physical actions
performed on soap bases to transform them into soap tablets. The processes by which soap bases are formed by chemical reaction
(saponification) are not included here. The manual only relates to SUNLAB machines and equipment.
(2) PROCESSES
Soap bases for the finishing operations are generally purchased in the form of noodles or chips. The colour, fragrance and other
ingredients are added and mechanically mixed so that they are evenly distributed throughout the base.
To produce a homogenous material the soap mix is subjected to heavy mechanical working by means of a triple roll mill or a refining
plodder. This not only intimately mixes the base and additives but also refines and to some degree physically modifies the soap structure.
The machines produce either compacted ribbons or noodles of soap which are then compressed and extruded in continuous bar form by
a plodder. The extrusion is cut into lengths by a soap cutter and finally stamped in a press fitted with a mould to give the desired shape
and weight.
The soap finishing processes may be summed up as:-
OPERATION MACHINE
Weighing of additives Digital scales
Rough mixing Paddle type mixer
Homogenous mixing/refining Triple roll mill or refining plodder
Compressing and extruding Extruding plodder
Cutting to length Cutter
Forming to shape Stamper fitted with a mould
(3) EQUIPMENT
(3.1) MIXER – Generally described as a tilting type paddle mixer, its function is to coat each noodle with a small amount of the additives
thus ensuring even distribution throughout the mix. It is suitable for processing up to 6% of liquid additives to the soap base.
(3.2) MILL – Our mills are equipped with three rollers each rotating at different speeds so that the soap passing through them is subject
to a grinding and tearing action modifying the physical structure and mixing the base and additives thoroughly. The working of the soap
is beneficial to the lathering characteristics and can give a slightly harder soap with fewer tendencies to absorb water.
(3.3) REFINING PLODDER – This machine performs a similar function to the mill but the action is not so severe. It can be used as a
cheaper alternative to a mill although modern production lines generally incorporate a mill as well as a refining plodder.
(3.4) EXTRUDING PLODDER – The millings from the mill or noodles from the refining plodder are compressed under considerable pressure
by the action of the screw (worm) forcing the soap through a warmed conical chamber and then through a die shaped to suit the cross
section of the eventual tablet.
(3.5) CUTTER – The extrusion from the plodder is cut into correct lengths for stamping.
(3.6) SOAP PRESS or STAMPER – The stamper provides the force to form the soap into the shape of the mould.
(3.7) SOAP MOULD or DIE – Determines the shape of the tablet.
(4) EQUIPMENT SELECTION
(4.1) MIXER – Two sizes are available; the 7.5M to mix 7.5kgs batches and the 25M to mix 25kgs batches. To mix a charge thoroughly
takes about 5mins, allowing for charging and discharging one mix could be achieved every 10mins.
(4.2) MILL – Three sizes are available; M75 (75mm diameter rolls giving 30kgs per hour), M100 (100mm diameter rolls giving 90kgs
per hour) and M150 (150mm diameter roll giving 180kgs per hour). Mills are fitted with hardened stainless steel rolls and can also be
fitted with water-cooling and temperature sensing.
(4.3) REFINING PLODDERS – These come in three sizes (measured by nominal inside barrel diameter), 100mm – P100, 125mm – P125
and 150mm – P150. They can be supplied with a variable speed motor which can be an advantage if a range of soap bases are to be
processed. The output of noodle soap is respectively 100, 130 and 180kgs/hr.
(4.4) EXTRUDING PLODDERS – These come in the same range of sizes as the refining plodders. It is a definite advantage to have a
variable speed facility for the extruding operation. Both to influence the finished appearance of the extruded soap and to control the
rate of production. Output of extruded soap will be approximately the same as the refining plodders.
Extruding plodders can be provided with refining/noodling heads which can be inter-changed with the extruding head so that only
a single plodder is required for the two operations. Obviously the output will be reduced inversely by the number passes of the soap
through the machine.
(4.5) EXTRUDING VACUUM PLODDERS – A vacuum facility can be provided for the three sizes of extruding plodders.
This is achieved by reinforcing and enclosing the hopper. It is useful if soft mixes or translucent bases are to be processed.
The disadvantage is that the machine has to be stopped and the hopper recharged.
(4.5) SOAP CUTTERS – For cutting the soap extrusion into predetermined lengths these are available in a variety of designs.
Hand operated cutter HSC, foot operated cutter FSC, semi-automatic pneumatic cutter LMKPC and automatic rotary cutter.
The first three are suitable for cutting extrusions of all shapes and sizes. Selection would normally be determined by the
quantity to be produced. The rotary cutter requires a different cutting head for each significant variation of length to be cut.
It is more suitable for long runs.
(4.6) SOAP PRESS / STAMPER – Two forms of stamper are available; a manually operated model LMK1 which has a maximum soap
bar capacity of 80g and two semi-automatic pneumatic machines Joraco 1030 for soap bars of up to 80g and Joraco 1530 for
soap bars up to 200g. The manual machine has a rate of production of 6 bars per minutes, whilst the pneumatic machines can achieve
in excess of 10 bars per minute.
(4.7) SOAP MOULDS – There are two distinct types of soap mould:-
Capacity mould – in which a billet a little heavier than the final tablet is placed in the mould and the surplus squeezed out, thus
giving a tablet of uniform weight every time. The mould comprises a top and bottom section.
Collar mould – in which the billet is cut to the correct weight and all the soap remains in the mould. This type of mould produces
tablets with straight sides consisting of top and bottom sections which move up and down inside a collar.
Moulds can be engraved on both top and bottom faces, supplied with an easy release surface or with facilities for cooling.
For costing purposes we divide moulds into simple and complex shapes. The former is defined as being capable of being produced
by a form tool moving in two directions (x and y axis). The latter requires movement of the tool in three directions (x, y and z axis)
and is characterised by multi directional curves.
(4.8) SELECTION CONSIDERATIONS - The main considerations may be summarised as follows:
(a) Volume of output.
(b) Size of tablet.
(c) Type of base.
(d) Economic circumstances.
(a) Volume of output – the overriding factor in plant selection is generally the amount of soap required to be produced.
The maximum rate of production from a combination of the above machines would be about 150kgs/hr and the minimum from
a single machine 20kgs/hr.
(b) Size of tablet – the maximum size of tablet from any machine is a factor of the ratio of the barrel diameter to the aperture of
the die plate. The larger diameter of the barrel the larger the aperture can be and therefore the larger the extrusion before there is
insufficient pressure to produce a compact extrusion. The P100 series can produce tablets up 100g, the P125 up to 125g and the P150
up to 150g. Extrusion under vacuum can increase these weights by as much as 20%.
(c) Type of base – in general we do not recommend the use of economy bases particularly if the proposed tablet size is near the
maximum for the machine. The results are likely to be disappointing. If the proposed base is other than a manufactures premium
type or if it is not a tallow/coconut or palm/coconut but is something a little special such as a translucent or syndet then we would
need to make a specific recommendation.
(d) Economic considerations – these considerations will vary from one environment to another we don’t have a set combination of
machines to produce a certain quantity of soap. Selection can be made on the basis of minimal investment where capital is at a
premium or minimal labour costs where employment costs are paramount.
(5) BASIC MATERIALS
(5.1) SOAP BASES – formed by the action of alkali’s of sodium or potassium on fatty acids and neutral oils from animal and vegetable
sources. Typical bases – tallow/coconut, palm/coconut or palm kernel
Ratio % – premium soaps 70/30
Normal 80/20
Minimum 90/10
The quality of a base is important from three major aspects:-
(a) Colour.
(b) Odour.
(c) Performance.
(a) Colour – of the soap base depends primarily on the fats and oils used. For good quality toilet soaps tallow and coconut oils are
bleached using activated earths. Where palm oil is used bleaching is essential. Base colour is important in determining the whiteness
of white soaps and the brightness coloured soaps.
(b) Odour – the base odour of soap depends primarily on the quality of the fats used and on the subsequent processes. For premium
quality soaps deodorising is usually carried out in addition to bleaching and stabilisers are added. Base odour is very significant when
it comes to perfuming the soap and must be taken into consideration by the perfumer.
(a) Performance – the major factor determining lathering performance is the ratio of tallow/coconut or palm/palm kernel. If the
ratio 70/30 is taken as the recommendation for premium soaps then as this moves towards 90/10 there is a noticeable decrease in
performance. Lathering is improved with the increased proportions of coconut but at the expense of noticeably more irritation to the
skin. The addition of 5-10% free fatty acid promotes skin mildness and at the same time the volume and lather performance increase.
There are several ways of increasing the free fatty content. The commonest is the addition of distilled coconut/palm kernel fatty acid
which is liquid at about 20-26 C. Added at the mixing stage. Good quality soap bases will contain a suitable preservative system to
prevent deterioration during storage and shelf life.
(5.2) FRAGRANCES – Soap fragrances need to be specially developed to suit the intended environment. The perfumer has to take into
account the reactive nature of soap and the conditions that it will be subjected to before and during use. Consideration needs to be
given to the following:
(a) chemical composition of the base i.e. free alkali, sodium chloride content, added preservatives etc.
(b) natural odour base.
(c) Physical shape of the tablet. Experiments show that the loss of an aroma chemical is determined by the rate of diffusion through
the soap matrix. Thus at a given time the concentration of aroma chemicals will be less at the surface than at the centre and thicker
sections will retain them longer than thinner ones.
The perfuming soap is a science and an
art and very defiantly the province of the expert. Even acting on the advice of the expert soap fragrances must be product tested by
incorporating them into trails bars and subjecting them to tests to determine colour stability, satisfactory self life, performance in use
and health and safety aspects.
The proportion of fragrance added to toilet soaps ranges from between 0.5 and 2%, with the norm being about 1%.
(5.3) COLOURS – These may be supplied as powders or in liquid form and are specially developed for incorporating into soap bases.
They need to be ineffective by the soap base, fragrances, light and to be stable over long periods.We recommend the use of powders
in SUNLAB mixers as these appear to be distributed more readily and helps to keep the liquid additions to a minimum.
(5.4) TITANIUM DIOXIDE – the prime function of the substance is to whiten the base for white soaps and act as a pacifier and colour
enhance for coloured soaps. The quantity added varies from 0.2 – 0.3% for coloured soaps to 2 or three times as much for white soaps.
(6) PLANT LAYOUT
The machines should be arranged in the sequence of operations i.e. mixer – mill – refining plodder – extruding plodder – cutter – stamper.
There should an area allowed for the storage of soap noodles, a bench for the preparation and weighing of additives, an area for the
temporary storage of tablets and packing area.
(7) MANUFACTURING OPERATIONS
(7.1) WEIGHING OF ADDITIVES – Accurate weighing scales to 0.1g will be needed. Colours particularly powder pigments as they are so
concentrated can be difficult to measure accurately enough to ensure uniformity between batches. One way of ensuring this is to prepare
sufficient for the complete batch or days production and then to bulk it up with one or some of the additives such as titanium dioxide.
The increased bulk can be more accurately weighed for each mixer load. Dilution as a suspension in distilled water or a liquid additive are
other ways.
(7.2) MIXING – the prime object of this mixing operation is to coat each chip or noodle with a small amount of the additives. Dispersal of
the additives is effected by the noodles tumbling and rubbing against each other so one with a high concentration of additives transfers it
to one with a lesser concentration. Over mixing will result in the breakup of the noodles and may lead to concentration of pigment etc
forming. Likewise the addition of too much liquid will cause clogging and inhibit the free movement of the noodles. Larger than
recommended liquid additions can be made in two stages with a refining or milling operation in between.
(7.3) MILLING – Generally two passes through the mill will be needed to give a reasonable distribution of the additives and adequate
physical working of the base, however if there is a refining plodder in the line only one pass should be necessary. The first pass through
mill is liable to be slow because the outside of the will be slippery due to the additives. If there is a refining plodder in the line then it
should be placed before the mill as slippery noodles have no detrimental effect on the performance of the plodder and the resulting
noodles from the plodder will be readily processed by the mill. It is generally beneficial to extrude the mix immediately after milling
while the mass is still warm. However with soft mixes it may be better to allow them to cool a little, so that they become a little harder.
(7.4) REFINING/NOODLING – Used either as a sole means of creating a homogenous mix or in conjunction with the mill. If used as the sole
mixer the soap will need to be passed twice through the machine or two machines will be needed operating in series. The soap mix is fed
into the hopper, either as noodles from the mixer or millings and forced through a fine mesh supported by a plate with a large number of
holes. The soap comes out as macaroni type strings which are cut into short lengths by a rotating multi-blade cutter. The mesh has two
functions to impede the passage of the soap resulting in a smearing action at the end of the worm and a shearing action as it passes through
the screen.
(7.5) EXTRUDING – This is the operation which is the most critical for the soap maker in the sequence of soap finishing operations. The soap
mix is fed into the machine in the form of millings or noodles. The worm forces the mix through first a graining plate which changes the flow
from rotary to linear movement and also creates some back pressure. Then into the compression chamber where it is squeezed and warmed
and finally through the die (extrusion) plate to form a shaped extrusion. Most soap bases are extruded at temperature of between 30/35C.
The greater part of this heat is generated by friction and compression as the soap passes down the barrel and part is added by the heater on
the nose cone, primarily to heat the extrusion plate to impart a smooth finish to the extrusion.
Excessive heat generated in the barrel will lower the friction between the wall of the barrel and the soap thus increasing the tendency for
the soap to rotate with the worm rather than being pushed forward by the worm. The result is a loss of output and possibly a drop in pressure
in the compression chamber. To avoid this condition the barrel is water cooled. In temperature climates mains water at 15/20 C is adequate
for this purpose. In hotter climes a water cooler may have to be incorporated in the water circuit.