This document discusses wash process design and additives for continuous batch tunnel washers (CBTWs). It explains that CBTWs divide the wash process into multiple sections to efficiently clean fabrics through mechanical action, time, temperature, water quality, and detergent formulation. Key factors discussed include using emulsifiers to remove oils, adding chemicals to neutralize alkalis or bleach, and selecting appropriate bleaches, temperatures, and detergents for different soil types.

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C
Washing Processes
LTC & DTC 2014
© LTC&DTC Ltd 2014

2. LTC
Wash Process Additives
EMULSION
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Emulsifiers
OIL
WATER
• An alternative way of improving the release of oily or
fatty soiling is to use an emulsifier in the wash. This
is a neutral liquid designed to help solubilise oily fatty
globules by splitting them and lifting them off the
fabric without aggressive chemistry.

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Wash process additives
Sour (Acid)
• To neutralise alkalis from the wash process
Antichlor
• To neutralise residual hypochlorite bleach
Fabric Conditioner
• To make the fabric feel ‘softer’ and reduce static
Starch
• Impart a ‘stiffer’ feel to the fabric-can be natural –
Rice or synthetic - PVA
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Wash Process Design
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Bleaches
Used within the wash or rinse sections depending upon the
type of bleach used.
2 Families of Bleach - Oxidizing and Reducing
Oxidizing bleaches for protein soiling and vegetable dyes
• Sodium hypochlorite - 60ºC Max – otherwise excess
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fabric damage
• Hydrogen Peroxide - 65ºC+
Reducing used to remove dye (Sodium dithionite/ Sodium
hydrosulphite)

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Sinners Circle – 4 principle
elements
DDeetteerrggeennccyy MMeecchhaanniiccaall AAccttiioonn
WATER
TTiimmee TTeemmppeerraattuurree
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Ingredients for a good wash…..
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WATER
• Quality – Clean, colourless, odour and bacteria free
• Soft (more than 5ºClarke – 72ppm too hard)
• Hard water contains Calcium and Magnesium Salts.
• Right amount in the right place at the right time at the
correct temperature

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Some problems caused by hard water
• Destroys some of the detergent
• Can make loads feel greasy if soap is within the
formulation
• Leads to scale build up in the CBTW which prevents
transfer occurring and can lead to blockages.
• Leads to a hard skin forming around greasy and oily
soiling making it harder to remove.
• Makes fabrics feel hard and harsh.
• Any water hardness has some effect on washing quality,
and the higher the hardness the greater the problem.
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Time
Different stages of the wash process need different amounts
of time. Typical examples are
• Pre-wash: 4-8 minutes to remove loose particulate soiling
• Main wash: 5-14 minutes to remove ingrained soiling
• Rinses: 3-5 minutes to dilute chemicals
• Spin: 3-8 minutes depending upon fabric type.
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Degree of Loading
• All washing machines are usually referred to by their
maximum loading capacity of dry 100% cotton textiles
(e.g. a 90kg machine). This figure is usually calculated
using dry 100% cotton sheeting as the standard
classification.
• Above this designated weight, mechanical action will be
reduced by the restricted movement and drop of the
linen. Overloading will therefore result in poor wash
quality.
• Below this target weight (under-loading), increased
mechanical action will occur which can increase fabric
damage. Wash costs also increase as the same amount
of water, chemicals and energy are used for a smaller
amount of work.
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Temperature
• Different types of soiling need different temperatures
(Oily – high, Protein Low)
• Fabrics, dyes and soiling behave differently at high and
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low temperature
• Chemicals activity increases with higher temperature

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Temperature
• 38ºC - Protein stains (blood and perspiration) start to set
above this temperature
• 40ºC - Optimum temperature for enzyme activity to digest
protein stains. Some enzymes are designed to work at
higher temperatures.
• 60ºC - Maximum temperature for sodium hypochlorite use,
to avoid fabric damage.
• 65ºC - Minimum temperature for using Hydrogen Peroxide
• 80ºC - Normal minimum temperature for heavy mineral oil
removal, but the latest systems can work at lower
temperatures.
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Detergency
• Each chemical reacts in various ways with both the
soiling and the fabric
• Detergency to match the particular stage of the
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process
• Chemicals are affected by the concentration (amount
added to the machine) as well as the temperature they
are used and the time which they have to react

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39ºC 75ºC 60ºC 25ºC
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Pre-wash
drain
Main-wash
drain
Rinse water
In /flow meter
Membrane press
Rinse Tank pump
drain
Wash flow
meter
Pre-wash
flush
Pre-wash
Flush pump
Wash Processes in a CBTW

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Time
12 stage CBTW - Total cycle time is 30minutes,
30mins÷ 12 compartments = 2½minutes
Therefore the process is likely to be set up
• Pre-wash/Wetting out – Sections 1 & 2 = 2 x 2½mins = 5
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minutes.
• Main wash stage – sections 3 – 8 = 6 x 2½mins = 15
minutes.
• Rinse stage – sections 9-12 = 4 x 2½mins = 10 minutes
• Total time: 30 mins.

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Mechanical Action
• Machine inner basket rotational speed – normally
pre-set during manufacture
• Correct reversing (to avoid tangles)
• Operational speeds - Rocking and Transfer (fabric
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type)
• Mechanical action from the contraflow of water
and/or the bath transfer

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Degree of Loading
• The principles of over and under loading apply with
CBTW’s. In CBTWs overloading has an additional
problem which can cause blockages.
• With CBTW underloading wash costs also increase as
the same amount of water, chemicals and energy are
used for a smaller amount of work.
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39ºC 75ºC 60ºC 25ºC
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Pre-wash
drain
Main-wash
drain
Rinse water
In /flow meter
Membrane press
Rinse Tank pump
drain
Wash flow
meter
Pre-wash
flush
Pre-wash
Flush pump
Water levels

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Temperature
• Within CBTW’s the same rules for temperature apply
for soiling types and fabrics.
• There are inbuilt inflexibilities with using CBTW’s as it is
a continuous process which must be taken into account
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39ºC 75ºC 60ºC 25ºC
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Pre-wash
drain
Main-wash
drain
Rinse water
In /flow meter
Membrane press
Rinse Tank pump
drain
Wash flow
meter
Pre-wash
flush
Pre-wash
Flush pump
Temperature

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Detergency
• The rules on detergency still apply
• Within CBTW’s there are inbuilt inflexibilities which
must be taken into account
• Careful detergency planning and management will
give you flexibility in soil removal
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