Evaluation of a Shampoo

7/27/2019 Evaluation of a Shampoo

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THE EVALUATION OF A SHAMPOOBy WM. W. MYDDLETON, D.Sc., F.R.I.C.*

THE SHAMPOO ser is supremelyconsciousof one characteristic, foam-iness, which, therefore, above allothers, influenceshis judgment ofshampooquality. The fact of theindependence f foaminess nd thecleansing action, for which pre-sumably he shampoos purchased,brings about no relaxation in thegeneral demand for a shampoowhich lathers freely. In 'this paperit is proposedo dealwith the assess-ment of shampoo alue on the basisonly of foaming power, which isthe veritable sine qua non of thepopular shampoo.The evaluation of a shampoomaybe required either for the majorproject of assessinghe appeal ofthe product to the shampoo-usingpublic or for quality control inmanufacture and for the selection,gradingand blending f raw mater-ials to be used in manufacture. Inthe presentdiscussion e shall con-sider only the assessmentor qualitycontrol and examination of rawmaterials. The ultimate test ofshampoo quality must be its per-formance on the head, but, as weshall see, great care must be taken

* Chief Chemist, County 12erfumery Co.Ltd., London.

in the planningof the test and in theinterpretation of the results. In apractical shampoo test we have todecide irst of all who is to operate,who is to make the observations,and on what type of head the test isto be applied. Secondly,we mustknow what observations are to bemade, and what conditionsof opera-tion will provide the most reliableinformation.It will be useful for us to examinefirst of all the nature of the evidencewe require to collect. It mustcover all those features which thecritical user will expect to find in ashampoo, namely:

(a) The product must have anattractive appearance. (Weare not consideringhe attrac-tiveness of the pack or itspresentation,but of the sham-poo material itself.)

(b) It must be simple n applica-tion, for example, if it is acream shampoo it must beeasily extruded from a tubeand easily spread on the hair.If a powder, it must dissolvereadily without scattering rri-tant dust.

(c) There must be no failure tofoam on the first application,150


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and the first rinsing shouldremove practically all the dirtfrom the hair. The secondapplication must produce acopious ather.(d) It mustbe easily insed utofthe hair.

(e) The hair must be clean andglossyand in good conditionwhen dry.

(f) The perfumemustbe pleasantthroughout he operation.(g) There must be no scalp rrita-tion.For purposesof control.we cancarry out only a limited numberofshampooests o determinewhether

the shampoo s capable of fillingthese requirements. The shampoowhenapplied o one'sownheadcan-not be used so effectively and easilyas when it is applied by a secondperson,who is also better able tojudge the cleanliness,gloss andgeneral onditionof the hair. It istherefore essentiM that the opera-tion should be carried out by someexperiencedersonwhowouldnatur-ally be the one to make and recordall the observations,with the excep-tion of suchas (g).We have now to consider somevariables n the working conditions.The most mportant s that all headsare not alike in their reaction to ashampoo. For example, greasy ordirty hair will tend to depresshelather of the first application andmay evensuppresst entirely. Notonly so, but the very texture ofthe hair, whether fine or coarse, 511affect lathering power.

For this reason, when only alimited number of test shampooscan be carried out, it is desirable todivide the hair into two parts, leftand right, down the middle line.One side is treated with a referenceshampoo and the other with theone under examination.

It must be observed here that,while we are by this means educinga major cause of discrepancy,weare introducing a minor one. Thepositioning of the operator withreference to the two sides of the headmakes t easier or him to manipulateone side than the other, and this isquite apparentat times, particularlywhen a fatigue effectdevelopsn thecourse of the somewhat strenuousapplicationof the shampoo. Thisdisturbing factor is miniraisedwheneach shampoo s used on an equalnumber of left and right sides.The saloon method is made moreselective by diluting the shampoobefore use with tap water to somearbitrary standard of concentrationwhich may differ according to thepurposeof the test. Very high con-centrations fail to show minordifferences nd may not reveal whatwe are really most concerned infinding, namely, whether a givenshampoo s likely to fail to producealather on the first application in asignificant number of cases, underthe average variations in the condi-tions of customerusage.

A useful level of concentration isaround 0'25 per cent of activefoaming agent or, if this should bedifficult to assess, '5 per cent for apowder shampoo,1'0 per cent for a151


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cream and 2 per cent for a liquidshampoo.The comparisonof shampoosofdifferent or unknown compositionmay convenientlybe made at aboutthe level of concentration indicated,bur adjusted to give solutions ofequal cost.The lathering power can be ex-pressed n terms of the total volumeof solution of the adopted concentra-tion required for the production offree lather on one averagehalf headof hair in a first and a secondapplica-tion, with intermediate rinsing.A point of great interest isobserved when a head chosen atrandom is submitted to a weeklyquantitative shampoowith the sameproduct. The volume of solutionrequiredwill normally fall from weekto week until in the fourth andsucceeding treatments the amountused becomes constant.

The saloon test is tedious and takesthe time of two people or each unitof test; a reliable udgment requiresa number of tests to be carried outon different types of head, thusadding greatly to the cost of testing.It is imperative, herefore, o providesomesimplermethodof testingwhichwill give results n agreementwiththe averageof an adequatenumberofsaloon tests on varied heads. Sucha simplified est can hen be usedasascreen to eliminate unsatisfactorysamples and materials from themore elaborate and costly saloontestings.Foamingpowerhasbeendescribedas a vital criterion of shampoovalueto the user, and for this reason a

methodof measuringoamingqualitywould be admirable as the screeningdevice.

Many testsof foamingpowerhavebeen described from time to time, andan excellent rdsum up to 1943 hasbeen made by S. Ross, Ind.Chem., 15,329, 1943.

A method will now be describedin which variables incidental to suchmeasurements are reduced to aminimum. The results agree wellwith actual shampoo tests carriedout on the same samples.In Fig. I the apparatus s shown oinclude two 250 mi. cylindricalseparating funnels with shortenedstems which are joined by means ofa length of rubber tubing. Onefunnel A, which forms an upperwater reservoir, s supportedso thata mark C indicating the level of150 mls. of water in the funnel isabout 17 inches above a referencemark D on the lower end of thesecond funnel B which acts as thelow-level water reservoir. The lowerfunnel is fitted with a rubber stoppercarrying a rubber connection to a35 cm. stemmed sintered glass disc of porosity No. 1. The disc isplaced n a 250 mi. graduated glasscylinder F, 1 inch in diameter, sothat it facesupwards,resting on thebottom of the cylinder with the steminclined diagonally n the cylinder.The cylinder'is placed n a wide glassjar G which acts as a water bath.In setting up the apparatus wateris poured into the funnel B andsuckedup into A, filling the rubberconnecting tube completely andreaching the level of the 150 mi.

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A

D

G

C

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JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTSmark. The lower level of the water isadjusted o the referencemark D. Astopper and tube are fitted in theneck of A for sucking water fromB into A.

The measuring ylinder s removedand the water-bath partly filled withwater at 30 C. 50 mls. of shampoosolution, also at 30 C., are pouredgently into the cylinder which isthen returned to the water-bathafter lowering the sintered glassdisc into it.

With the tap of B open he tap ofA is opened to force air from Bthrough the sintered disc, and pro-duce a foam in the measuringcylinder. As soon as 150 mls.of water have passed rom A to Bthe tap is closedand a stopwatchstarted. At once he top and bottomlevels of the foam are read off inthe cylinder F and the same levelsare read at intervals over a period of10 minutes. From these readingsthe decrease in foam volume andalso the increase in drainage ofliquid from the foam are calculatedand graphedagainst ime in minutes.The concentration of the solutionused for test may conveniently beat the level indicated for the saloontests.

It has been mentioned that thenatural or added greaseon the hair,togetherwith any depositsrom hairdressings nd otherhair preparations,tend to reduce the amount of foamproduced n the first application fa shampoo. Solutionsof shampoosmade up in hard tap water or indistilled water do not reveal minordifferences n foaming power in the

apparatus described, and to makethe methodserviceablet is necessaryto add to the solution a suitable anti-foamingagent. This would appearto be an opportunity to introduceatype of anti-foaming agent to simu-late the behaviour of the substancesnormally presenton dirty and greasyhair. To achieve his would equirethe introduction of an insolubleoilyphase such as a mixture of mineraloil and lanolin and a solid phasesuch as lampblack.The difficulty is then created hatthe anti-foaming system is notdisperseduniformly through eitherthe liquid or the foam and is unevenin effect. It is for this reason thatsecondary butyl alcohol has beenchosen for its solubility and it isrecommended at a concentration of5 per cent by volume n the tap waterin which the shampoo s dissolvedfor the test.

The optimum conditions or usingthe apparatus are:1. A room of reasonably constanttemperature and free fromdraughts.2. The sintered glassdisc must beof known porosity for purposesof replacement and duplicationof apparatus. A suitableporos-ity is No. 1.3. The diameters and lengths oftube connections and bores of

stopcocksmust be capable ofallowing a flow of 150 mls. ofwater from A to B in 20 to30 secondswhile foam is beingproduced.

4. The stem of the sintered glass154


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120

100

80

dO

,40

2O

0 1 2 3 4 5 6 7 8 9 10 11--- TIME IN MINUTES

DECREASEN VOLUME OF FOAM V. TIMEQ CommercialodiumaurylulphatenTapWater ButyllcoholR as m q but ncludingauryl lcohol$ CommercialodiumaurylulphalenTapWaterT Commeraalodiumauryl ulphaten Distilledater1mlofall oluhons4 mls. /S00 elylrlmelhyJammonlumromide

FIG. 2

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.

disc must be placed diagonallyin the cylinder, otherwise acollapse of foam may occurbetween the tube and thecylinder.All parts of the apparatuscom-ing into contact with the foam-ing liquid must be well washedwith 5-10 per cent hydro-chloric acid and then two orthree times with distilled waterafter each alternate estimation.The water levels in the cylin-ders A and B must be main-tained by adding water asevaporation takes place.

Under these conditions:(1) Foam is produced in everycase rom essentially he same

volume of air.(2)The air is brokenup into bubblesof fairly uniform size.(3) The time of formation of thefoams s substantially the same

in all cases.(4) The foam comes nto contactwith surfaces free from uncon-

trolled insoluble films whichtend to destroy foam.

(5) The comparativeevaluationofa number of shampooson abasis of foaminess is repeat-able for one operator andapparatusand reproducible orother operatorsand apparatus.Some results of tests are shown in

Fig. 2, where t will be seen hat theaddition of butyl alcohol to the tapwater causesa more rapid declinein the volume of foam and thatthe addition of unsulphated lauryl

alcohol o the shampoosubstantiallyarrests the decline.In saloon ests he shampoowhichgave curve Q formed a more waterylather than that from which curve R

was derived, and required for itsproduction on an average approxi-mately 10 per cent more solution atthe concentrationdefined n Fig. 2.A steepercurve than Q connotesa watery lather which breaks downrapidly on the head and may lead toabsolute failure to lather on the firstapplication. Although the shampoouser normally applies a much higherconcentrationof shampoo han thatemployed in the saloon tests de-scribed, the difference in qualitybetween, for example, the shampoosQ and R is quite distinct on someheads.

However important the practicalshampoo est in the saloon may be,it is quite clear hat a tekt on a singlehe/td can be misleading becausedifferent heads are not shampooedwith equal facility. On the otherhand, a single foaminess est carriedout in the apparatus describedwillindicate a good shampoo which isabove suspicionor a poor one whichit is useless o consider further, or itwill bring out the intermediate casein which further examination bysaloon est on severalheads s highlydesirable.

ACKNOWLEDGMENTThe author wishes o expresshisthanks to the Directors of CountyPerfumery Co., Ltd., for permissionto publish this paper.156

Evaluation of a Shampoo

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