Foam Technology

Reduce or eliminate the use of water

Conserving or saving energy

Developed in the 1980s

Water is used in foam technology but in a much smaller quantity than conventional coloration

methods.

CAV- Critical Application Value. CAV of 40

Pick up (%) is around 20. We need the liquor to transfer the dye inside the fiber interior. Not just

on the surface!

Spraying or padding involves using the pure liquid but when using foam for coloration, foam is

just going to be the transfer medium.

Types of Foam:-

- Solid foam (PU foam, PS insulation material etc.). Air is trapped inside in bubbles. Another

example includes cellular plastic where air cells are entrapped inside the expanded plastic.

Air is trapped inside in bubbles. Other examples of solid foam include bread, meringue etc.

which involves the disperse phase being gas and the dispersed medium being solid.

- Solid foams are used mainly in the preparation of insulation and in upholstery and even

found in pumice stone (lava; pumice stone being used in garment washing (denim washing))

- For textile use, we use “Gaseous foam” where the dispersed phase is water and the

dispersed medium is gas or air. E.g. of gaseous foams include egg whites, whipped cream,

beer. Here, Foam is a material of tiny air bubbles separated by fine films. The mass of air

bubbles are separated by thin films, being dispersed in liquid medium.

- Gaseous foams: Dispersed phase being gas and the continuous phase being water. Gaseous

foams serve as the transport medium or vehicle for textile chemicals like dyes or finishing

formulations to reach the substrate.

- Foams are more used in textile finishing than dyeing.

- Condensation Foams: This involves gas entrapment in a liquid. Eg. Soda pops. Or when

applying bicarbonate in a liquid, heating it to produce carbonate and CO2 gas. This gas forms

internally in the liquid being entrapped or dispersed in the liquid. [Carbonated drinks].

- “Generation of gas within the liquid either by chemical action or by physical by physical

means”. Eg. Changed in temperature and pressure.

*Remember, solubility increases with increasing temperature for a solid but for a gas,

solubility decreases with increasing temperature! So cool temperatures give higher

solubility.

- Solid foams like PU foams are a kind of condensation foam. Eg.

-N=C=O + H2O -NH2 + CO2

Here the CO2 gas gets entrapped in the PU, creating the solid PU foam.

- Dispersion Foams: These are produced by introducing and mixing a gas in a liquid phase.

E.g. whipped cream.

- Foams are applied in textiles as a dispersion type in which the liquid phase is water and the

gaseous phase is air.

- Due to buoyancy, just whisking isn’t enough to create the dispersion. A surfactant needs to

be added to hold these two phases from separating. This way the surfactant acts as a

‘foaming agent’. In textile foam processing, this foam is always used.

Important Aspects of Foam Processing:-

Reagent is applied to the fabric in the form of foam in contrast to conventional processed

impregnating the substrate in a solution of the reagent. As air replaces water as the transfer

medium for the reagents, the following advantages are gotten:-

- Reduced heating and drying costs of the fabric

- Saving chemicals, water and energy

- Less water to treat in the effluent

- Less waste disposal

- Improved quality of the product

Nature of Foams [Structure and Characteristics]:-

Foam is an agglomeration of gaseous bubbles (usually of air) dispersed in a liquid and separated

from each other by thin films or lamellae. It is these films which carry the dye finishing chemicals

or reagents.

There are two types of foams, spherical and polyhedral foams:-

Spherical Foam Polyhedral Foam

Spherical foams consist of individual, independent bubbles. Their creation doesn’t require the

use of a surfactant and their stability only depends on the viscosity of the dispersion medium.

At high viscosity, the lifetime of the foam is considerably lengthened.

Polyhedral foams only develop in the presence of surfactants.

Diagrammatic representation of foam structure:-

The

Spherical foams have 0.04 inch film thickness (1mm)

Polyhedral foams have 0.0004 inch film thickness. (0.01mm)

Spherical foams consist of a concentrated assembly of accumulation of discrete spherical

bubbles in a liquid spaced at distances greater than their diameter.

Polyhedral foams (most used is hexahedral) are aggregations of closely spaced polyhedral

shaped bubbles which burst almost immediately after they are formed.

Stable foams can be used in printing, sizing etc.

The bubbles vary in size from 50 mm to several millimeters. However for foams used for textile

purposes, size ranges from 50 – 100 m.

Bubbles MUST break up during application.

Properties of Foam:-

1) Foaming Degree

- Gives a measure of the extent of foaming. Its an indication of the volume of foam produced

from one liter (1 L) of liquor. Liquor is not just water. It consists of water + dyestuff +

auxiliaries or finishing formulation.

- Foaming degree is usually expressed in terms of foam density (g/L).

Foam density lies from (0.07 – 0.14 g/L) for Foam Finishing.

Foam density lies from (0.20 – 0.33 g/L) for Foam Printing.

- Another expression for Foaming Degree is ‘’Blow ratio” or

“Expansion ratio”.

- Blow ratio is defined as the ratio of mass of a given volume of

liquid before foaming to the mass of the same volume of foam.

Eg.

- For example, if 100ml of a foam weighs 10g and 100ml of the liquid weights 100g-

- For textile purposes, the blow ratio is 10:1 – 12:1

2) Foam Stability

- Change in density of the foam per unit time.

- Foam stability is a measure of the time taken for a foam to maintain it’s initial properties

(foam density, blow ratio etc.) after being generated.

- Foams that are very stable are difficult to collapse or rupture cause poor penetration of

formulation into the fabric.

- Similarly foams that are relatively unstable collapses before printing applications can begin,

resulting in uneven distribution of chemicals on the substrate surface.

- Half-life of foam :-

Foam stability can be expressed in terms of half-life t1/2

Half –life of foam is the time required for half the volume of the liquid contained in the foam

to drain to the bulk-liquid phase.

- Shorter the half-life lower the stability of the foam.

- Half-life of foam in other words can be defined as the time taken for half the contained

liquid in the foam to drain down to the bulk-liquid phase.

- Too high a stability of the foam and an anti-foaming agent is required.

- Foam’s half-life range:

- Foam’s half-life range according to the type of process making use of foam technology:

3) Foam Viscosity

- Measure of the foam’s resistance to flow.

- Foam viscosity is an important parameter as it influences foam performance. Eg. In coating

application, ease with which it can be handled, processed or used.

- Spray gun is often fitted in applicators in order to dilute or “thin” the foam or reduce the

thick foam’s viscosity when required.

4) Foam Wetting Power

- For an even surface distribution

- Rapid wetting by foam or rather by the liquid formulation collapsed and released by the

foam upon contact with the textile material, is a very important property where application

in textile finishing is concerned.

5) Bubble Size and Distribution

- Narrow range or distribution of bubble size is required (less variations = better dispersion).

Foam Processing (Block Diagram)

Sequence of Processing:-

1) Liquor Preparation

Essential ingredients go into the recipe for the preparation of the liquor to be used. Careful

attention is needed with regard to the individual components mixed.

Recipe for liquor :-

- Functional reagents (Colorants like dyes or pigments, finishing formulation chemicals etc.)

- Foaming agents (Surfactants)

- Viscosity modifiers (Thickener)

- Foam stabilizer (Stabilizer)

- An emulsion polymer copolymer

- Other additives, e.g. catalyst, wetting agent, fillers, pH buffer, biocides, bactericides,

insecticides etc.

(l) Functional Reagents

Includes colorants and finishing chemicals

(ll) Foaming Agents (Surfactants)

Use of a mixture of surfactants of different ionic nature in the liquor helps to obtain synergistic

effects in the foam to be produced.

Surfactants help promote foam generation under mechanical action. It helps to hold the two

phases together and prevents their separation.

Surfactants used. E.g. Anionic, Cationic, Non-Ionic, Amphoteric (or zwitterionic) – All are suitable

as foaming agents.

Class Surfactant

Anionic

Sodium or Ammonium Stearate

Sodium Oleate

Sodium Dodecyl (or Lauryl) Sulphate

Sodium Dodecyl Benzenesulphonate

Cationic Dodecylamine hydrochloride

Non-ionic Polyethylene oxide condensates / ethoxylated

alcohols, carboxylic acids, amines, amides etc.

Amphoteric Alkyl betaine surfactant

(lll) Viscosity Modifier

Thickeners are used which modify the viscosity so that the bubbles remain separate and

homogeneous.

Thickeners increase the viscosity of the compound thus slow down the drainage of the

interlamellar liquid (increase foam stability). Foam life is thus prolonged.

Examples of suitable thickeners (both natural and synthetic) include:-

- Locust bean gum

- Guar gum

- Methyl cellulose

- Hydroxy methyl cellulose

- Polysaccharides

- Sodium alginate

- Xanthan gums (These give highest thickening ability)

(IV) Stabilizers

These are used in combination with thickeners.

These are substances that doesn’t thicken but are added to improve foam stability

further, through enhancing thickening ability.

Eg. Sodium polyphosphates and Dodecanol (Lauryl alcohol) C12H25 –OH

(V) Emulsion Polymers or Copolymers

Colloidal dispersions (aqueous or water based) used to modify physical properties of

finished fabrics (these are only used in special cases when processing with foam).

E.g. Common types of polymer emulsions used include PVC and Polyacrylates

2) Foam Generation

Considered to be the heart of foam processing

There are various foam generations that are available and principles on which they

operate.

Quality of foamed compounds is influenced by the quality of air dosing. An accurate

blow ratio is required. Smallest fluctuations in air content changes the liter weight of the

foam and consequently the quality of the product.

Air injections have to be controlled with the liquor being flowed in at the same time.

Measurement of the flow rate is of equal importance in controlling the foam quality and

thus the end product as well.

Foam generator: used for the mixing of both air and liquor to create the foam.

Sample diagram of a foam generator:

There are two methods available

- Air blowing method

- Stirring method

Foam generation is achieved by vigorous mechanical agitation, air being supplied or injected at

high pressure (Air Blowing) or captured from the atmosphere by the turbulence of the liquid

(through agitation by the stirrer), a combination of these two methods may also be used.

Air Blowing type of foam generation may be either static or dynamic.

In the static mixer, a stream of air under pressure is

introduced into the liquor to produce irregular

shaped bubbles. Liquor & air are brought into

contact with each other in a mixing head containing

glass beads / stainless steel shavings/ plastic

shavings.

The static mixer can also have a vertical arrangement too instead of a horizontal one.

In this static foam generator, a stream of air under pressure is introduced to the liquor to

produce irregular shaped foam bubbles. Foam can also be generated by feeding a liquor

together with air through a chamber containing a number of closely packed glass balls, stainless-

steel shavings, plastic or chips.

Both air and liquid are metered into the head where they are mixed to produce the foam.

The liquid and air pressure push the foam out- to the point of application.

A dynamic mixer or foam generator consists of a stator and a rotor as shown:

Air under pressure + liquor are metered into the mixing head and the foam exits after

getting produced .

The rotor and stator are constructed to have a close arrangement by which the

air+liquor mixture is repeatedly sheared and mixed during this mixture’s passage

through the head.

Speed of the rotor, Clearance between the protruding components, Input rate of air and

liquor are factors influencing the pressure developed in the mixing head.

Equally important is the hose length between the foam generator and the application

point to provide sufficient back pressure.

Size of this system is somewhat reduced, the ease of cleaning is improved and the

system offers more constant conditions that the static mixer.

This system has better control over foam supply quantity, air dosing and gelling agent

quantities according to the speeds of the coating plant.

These computer assisted systems represent the present state-of-the-art.

Stirring Method

Combination of Air-

Blowing and Stirring

Method

*Note that all methods of foam generation mentioned so far are all batch methods.

3) Foam Application

- The systems of foam application include:

Direct System (Pressurized and Non-Pressurized)

Indirect System

Direct systems involve foam directly being applied to the fabric with this foam being held under

pressure in the distribution box. Foam application to the fabric is done through a variable-dimensional

slot applicator or through a rotary screen with the fabric pressed against a backing roller.

1. Direct system (Pressurized System)

2. Direct system (Non- Pressurized System)

- In the non-pressurized system, the reservoir of foam is not maintained under pressure, but

this doesn’t mean that there is no pressure involved during application. The foam gets

applied to the fabric by a horizontal pad or by a knife-over-roller, knife-on-air or knife-over-

blanket application system.

- In the horizontal pad-system, the fabric is introduced vertically through the nip point

between two rotating rollers and the foam can be fed at the appropriate rate to either or

both sides of the moving fabric. This allows simultaneous application of different finish on

both sides of the fabric!

- In the knife-over-roller, the knife- on- air and the knife-over-blanket techniques, the foam

is supplied to the moving fabric at a certain point against the knife, and the gap between the

knife and the fabric controls the application of foam. These techniques require the use of

stable foams which are to be destroyed after its application because the gap setting is the

major controller of pick-up (%) and the foam must not collapse and wet the fabric before

reaching the doctor knife, since otherwise a higher wet pick-up (%) may result.

3. Indirect system

- The first indirect system involves the use of a carrier/transfer or kiss roller. This carries the

foam along the circumference of the roller and transfers it onto the fabric.

The foam is metered by some means which is transferred to the fabric by the carrier roller.

The carrier doesn’t necessarily have to be a roller but can also a drum or a blanket.

Transfer of the foam is achieved as the carrier and fabric come into contact.

- Other systems have a similar approach. Foam is metered by some means on a carrier before

being transferred to the fabric. The carrier can be a drum (Janus) or blanket (Monforts), and

both there applicators are shown as follows:-

- Transfer of foam is achieved as the carrier and fabric come into contact. In the Monfort’s

system, transfer of foam is assisted by vacuum through the perforations of the carrier drum.

Monforts Vacu-Foam System

- The Monforts Machine, also known as Vacu-Foam, uses a knife-over-roller to meter a

uniform layer of foam on a rubber blanket.

- Transfer of the foam to the fabric occurs when the blanket makes contact with the fabric.

- Penetration of the foam into the fabric is assisted by vacuum as the fabric passes round a

perforated drum.

- Add-on is controlled by the foam density and knife clearance.

- Rate of foam collapse is depends on capillary forces, the vacuum created inside the

perforated drum and the pressure on the fabric.

- Wpu (%) for cotton is 35-40% and that for PET fabric is 10%.

- Even elastic warp-knitted fabrics and pile fabrics can be treated by this system. Its been

claimed that crease-recovery angle and abrasion resistance of the cotton fabrics treated

with foam were much better than conventional padding techniques.

Janus Mini-Foam System

- Kusters developed two foam processing systems, the Mini-Foam applicator for woven,

knitted and non-woven fabrics and the Maxi-Foam system for carpets and heavy pile fabrics.

- The Mini-Foam system is built in three standard models, for one sided application on the

face side of the fabric, for one-sided application on the back side of the fabric, and for

simultaneous two-sided application. The latter model being called “Janus Mini-Foam

applicator”.

- In the Janus Mini-Foam system, the foam is fed into the foam through a trough by an

oscillating feed pipe.

- The trough has adjustable sides, set to appropriate fabric width.

- An adjustable doctor roller at the lower end of the trough controls the amount of foam and

thickness of the foam layer (0.4 – 40 mm) on the rotating application roller.

- Foam is transferred and pressed into the fabric as it passes 180° around the application

roller. The foam is collapsed by capillary forces and pressure.

- The two distinct mechanisms involved are the application of foam to the application roller

and the transfer of foam to the fabric.

- The twin-roller Janus machine consists of two such applicators, enabling both face and back

of the fabric to be treated. Two different foam liquors can be applied separately but

simultaneously to the two sides of the fabric.

Parameters affecting the wet pick-up are

Speed of the application roller

Width of the gap between the doctor roller and the application roller

Foam density

Speed of the fabric

- Wet pick-up ranges from 15-30%

- Certain finishing chemicals are applied at a wet pick-up of about 35%.

- The two-sided application with one or two different foams is normally recommended for

woven and knitted fabrics of 150 gsm and above.

4) Foam Destruction

Foam needs to be destroyed on the fabric shortly after it is applied, releasing the

finishing liquor contained to take over as the transport medium. This allows the

reagents to penetrate and spread on the fabric before any fixation treatment is applied.

Manner of destroying the foam depends according to the method of application and

depends on the actual conditions of use.

Foam destruction is carried out mainly by

- Squeeze rollers of a conventional padder installed in front of a stenter

- Vacuum application

- Combination of these two methods

Foam destruction is promoted by:

- Capillary forces withdrawing the liquid from the foam lamellae and so reduces their film

thickness until the bubbles burst.

- Pressure, occurring during direct and indirect application, bringing the bubbles into close

contact with fibers, promoting bubble penetration and destruction.

- High drying or ambient temperatures causes lowered foam viscosity, increasing motion of

molecules in the lamellae and increasing the bubble volume. Plus, when surfactants are

heated beyond their turbidity point/ cloud point, they close their foaming ability and instead

function as destabilizers.

- Shear forces cause foam bubbles to burst by increasing their volume and weakening their

walls

- Defoamers; these are emulsions of an insoluble substance that contains organic solvents to

cause rapid spreading of the defoamer, as the defoamer is adsorbed onto the lamellae there

is a local increase in surface tension! The defoamer spreads out, carrying with it a thin film

of underlying liquid , therby thinning the lamella until it finally bursts.

5) Drying and Fixation

Drying and curing/fixation of foam-impregnated fabrics are usually done on traditional

machines (curing chambers and stenters).

Higher speeds and lower temperatures should be used since amounts of water to be

evaporated are much lower than those with a conventional pad-mangle finish

application system.

Advantages of Foam-application Techniques

Drying-energy costs are lowered due to low- add-on techniques used in foam application.

Drying-energy costs can be reduced by about 50%. The actual savings differ considerably and

range from as little as 15% to as high as 80%.

Drying temperature can be reduced considerably (by 65°C). Its also possible to maintain a

relatively high drying temperature but to increase the processing speed.

Water consumption is reduced by 30-90%. Reduction in the volume of effluent water. Effluent

treatment costs could be reduced by 50-80%. Air pollution is also reduced.

Chemicals are utilized more productively. Chemical consumption costs are reduced. Reduced

concentrations of auxiliary chemicals like printing thickeners. In some cases, some auxiliaries can

be completely removed from the formulation. Less dyestuff can be used than in conventional

padding processes. Chemical savings of less than 10% to up to as high as 50%.

Migration of DP or CRF resin finishes during drying is one of the most serious problems with

conventional finishing methods of cotton fabrics. This migration effect is reduced if wet pick-up

is reduced. Foam application this way reduces or eliminates this migration to produce a uniform

distribution of chemical on the fabric. This improves qualities like crease-recovery angle,

abrasion resistance, tear strength, tensile strength, bursting strength and resistance to flex

abrasion. Width shrinkage during washing can be reduced. Handle and wash-and-wear

properties of the fabric are also improved.

Elimination of pre-drying, making it possible to do wet-on-wet applications.

Different finishes can be applied to the face and back of a fabric. It is possible to dye the two

sides of a fabric independently in one process, for example, applying a basic dye to an acrylic

fiber pile face and a direct dye to a cotton back. Alternatively, one sided application is possible

too.

Delicate fabrics can be processed under low tensions by foam-application techniques.

Dye-yield can be improved. Rate of fixation of dyes is higher. Steaming times reduced. Washing-

off process time shortened. Rubbing fastness can be improved.

Volume of dye liquor can be reduced by 25-35%.

Printing with foam gives better quality, good definition with less strike-through and softer

handle. Washing-off of the printed fabrics can be reduced or even eliminated.

Disadvantages of Foam Application Techniques

Its essential to have well prepared fabric for foam processing. Variations in fabric absorbency

causes variations in wet pick-up leading to an inadequate and non-uniform chemical application.

At very low wet pick-up values, uniformity of application is critical and penetration of the

chemical into the fabric can be inadequate.

In cases where production speeds could be increases as a result of the lower wet pick-up,

certain drying units are not designed for such high running speeds.

In any low add-on application system, it is more critical. To maintain the same solids- add-on

level, concentration of chemical in these liquors are normally considerably higher than those in

conventional liquors!

Solvents and mineral oils used in certain processes will inhibit foam formation.

Certain optical brightener and softeners and the presence of sulfate ion from reagents reduces

foam stability.

Foams should generally be applied to both sides of a fabric.

Shades are difficult to match at low add-on levels.

It is difficult to produce deep shades at low wet pick-up (%) because of the limitations of

dyestuff solubility.

One important application method for chemical finishes is the use of

foam to apply the finish to the fabric. By replacing part of the water in

the chemical formulation with air, the amount of water added to the

fabric can be significantly reduced!

Surfactants are included in the formulation to be foamed.

The chemical formulation is mixed with air in a foam generator

producing high volumes of foam that can be applied to fabrics in a

number of ways.

The ratio of liquid to air in a foam is referred to as the ‘blow ratio’,

determined by the equation:-

Foam densities in the order of 0.1 g/cm3 are routinely used.

Stability of the foam is influenced by the components of the chemical

system, the viscosity of the foam and the method of foam preparation.

The half-life of a foam is the time in which 50% of the liquid is a given

foam has been drained from the foam to the bulk-liquid phase. Foams

for textile applications can have half-lives from a few seconds to

several hours.

One side applicators apply foam to only one side of the fabric, leaving

open the possibility of two different finishes on different sides of the

fabric. The two side applicators, on the other hand, apply the same

foam to both sides of the treated fabric.

Two side applicators normally employ two slots to apply the foam to

the fabric. Two distinctly different finishes can be applied to different

sides of the same fabric simultaneously.

Foam application on fabrics with large open spaces or non-uniform

porosity often causes uneven finish distribution.

Foam application systems also include horizontal pad mangles, kiss

coating systems, knife-over-roller or knife-on-air systems, screen

printing and slot applicators.

Proper fabric preparation is required in order to achieve uniform

finish distributions. A well-absorbent fabric is the best guarantee of a

proper finish application.

To maintain the same chemical add-on with lower wet pickups, the

concentrations of the finish bath components must be increased

according to the equation:-

conc2 = component concentration at the lower wet pick

conc1 = original concentration

density2 and density1 are the densities of the modified and original

solutions, respectively.

wpu2 and wpu1 are the lower and the original wet pickups

respectively.

Since the density of the more concentrated solution cannot be

determined until after the solution has been made, an initial estimate

of density2 is used in the equation, to calculate the approximate conc2.

Through successive iterations, more accurate values of density2 and

conc2 can be obtained if necessary.

Foam applicators:-

Foam applicators limit the amount of water added to the fabric by

replacing a portion of the water in the formulation with air.

A chemical formulation is mixed with air in a foam generator to create

a foam usually having fine bubble size.

Incorporating air into the formulation creates a large volume which

can be spread on the textile fabric more uniformly than can the

unfoamed liquid.

Relative amount of liquid and air in the foam are usually expressed as

the “blow ratio” of the foam. Blow ratio is the reciprocal of specific

gravity of foam. For instance, if a foam (made of only air and water)

weighs 0.1g/ml, the blow ratio is said to be 10:1 or 10 to 1. This

means that a foam having 10:1 blow ratio is 90% air and 10%

chemical formulation by volume.

Foams are inherently unstable and will separate into gaseous and

liquid phases as the foam ages. Relative stability of a foamed

formulation is important in foam application systems. Some methods

require very stable foams while others require very unstable foams.

Stability of a foam has to be tailored for the particular application.

Foam stability is expressed in terms of the half-life the foam. Half-life

of a foam is the time length of time required for half of the liquid in

the foam to drain out and become a separate liquid phase. Half-lives

of foams used in textile applications range from a few seconds to

many hours.

Two general types of foam applicators are called “open foam” and

“closed foam” processes. An open foam process is one in which the

foam leaves the particular generator and come in contact with the

atmosphere before being applied to the fabric.

In a closed foam process, the foam is trapped in the applicator under

pressure up to the point at which it contacts the fabric being treated.

Open foam applicators include knife coaters which spread the foam on

the fabric surface and the horizontal nip pad which coats the fabric

with foam and crushes the foam into the fabric as the fabric passes

through the nip of the rolls.

Wet pickup is determined mainly by the blow ratio of the foam.

An open foam process requires a foam of relatively long half-life since

the blow ratio must remain essentially constant at all times.

The closed foam applicator forces the foam under presser through a

slot, which is sealed by the fabric passing continuously across the slot.

The wet pickup is determined by the feed rate of the foam generator

and the speed of the fabric crossing the slot.

Foam having a relatively short half-life is preferred because the foam

should collapse upon contact with the fabric! The blow ratio and foam

pressure affect the degree of penetration of formulation into the

fabric.

Curved Blade Applicator

This applicator is designed for application of chemicals using limited

amounts of water, meters formulation onto the fabric at a

predetermined rate.

Formulation is delivered to the curved blade through a perforated

distribution pipe. Formulation accumulates in the weir (barrier or

block) and overflows down the blade to be deposited on the fabric

passing the tip of the blade.

Wet pickup is determined by the relative

rates of formulation feed and speed of the

fabric passing the blade.

Flow characteristics of the formulation are

critical since the blade must be completely

wet by the formulation to prevent

occurrence of untreated spots on the fabric.