KENYA STANDARD  DKS 508:2023 
ICS 59.080;11.040.30  
Fourth  Edition  
 
 © KEBS 2023  
  
  
Absorbent cotton wool  — Specification  
 
 DKS 508:2023 
ii © KEBS 2023 – All rights reserved  
 TECHNICAL COMMITTEE REPRESENTATION  
The following organizations were represented on the Technical Committee:  
Kenya Industrial Research and Development Institute  
Kenya Medical Association  
African Cotton Industries  
Chandaria Industries Ltd  
Ministry of Health (MOH)  
Kenya Défense  Forces (KDF)  
PadMad  
Kimberly -Clark  
Radbone Clark (K) Ltd  
Marvel Five Investment ltd  
Mbagathi County Hospital  
Procter and Gamble  
KIM FAY East Africa Ltd  
Onkod Company   
Mega Importers  
Maxcare Products Limited  
Kenya Bureau of Standards — Secretariat  
 
REVISION OF KENYA STANDARDS  
In order to keep abreast of progress in industry, Kenya Standards shall be regularly reviewed.  Suggestions for 
improvements to published standards, addressed to the Managing Director, Kenya Bureau of Standards, are 
welcome.  
© Kenya Bureau of Sta ndards  2023 
Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 130 of 2001 of  the Laws of Kenya, copyright subsists 
in all Kenya Standards and except as provided under Section 25 of this Act, no Kenya Standard produced by  Kenya Bureau of Standards 
may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing f rom the 
Managing Director.    
© KEBS 202 3 – All rights reserved  iii 
  
 
Absorbent cotton wool  — Specification  
 
 
 
 
 Kenya Bureau of Standards,  Popo Road, Off Mombasa Road,  
P.O. Box 54974 - 00200,  Nairobi, Kenya  
 +254 020 6948000, + 254 722202137, + 254 734600471  
 info@kebs.org  
 @KEBS_ke  
 kenya bureau of standards (kebs)  
DKS 508:2023 
iv © KEBS 2023 – All rights reserved  
 Foreword  
This Kenya Standard has been prepared by the Technical Committee on Towels, Medical and Hygienic Textile 
Products under guidance of the Standards Projects Committee, and it is in accordance with the procedures of 
the Kenya Bureau of Standards.  
 
 
Cotton wo ol is used for cleaning and swabbing wounds, pre -operative skin preparation, application of 
medicaments to wounds, for insertion to orifices such as ear and nose and for the preparation of swabs for 
taking specimens.  
 
This Fourth Edition cancels and replac es the Third Edition (KS 508:2009) which has been technically revised.  
The changes are as follows:  
 
-Title has been changed to ‘ Absorbent cotton wool — Specification ’ 
-Scope has been expanded to include cotton wool for both medical and general use  
-Require ments for ‘Length of staple ’ and ‘Total Viable Count have been reviewed ’ 
 
 
In preparation of this Kenya Standard reference was made to the following document:  
 
KS 508:2009  Absorbent cotton wool for medical use — Specification  
 
Acknowledgement is hereby mad e for the assistance derived from this source .  
© KEBS 202 3 – All rights reserved  v 
 Absorbent cotton wool — Specification  
1 Scope  
This Fourth Edition of this Kenya Standard prescribes the requirements for absorbent cotton wool for medica l and 
general use . 
2 Normative references  
The following documents are referred to in the text in such a way that some or all of their content constit utes 
requirements of this document. For dated references, only the edition cited applies. For undated references, the 
latest edition of the referenced document (including any amendments) applies.  
KS ISO 21149 , Cosmetics — Microbiology — Enumeration and det ection of aerobic mesophilic bacteria  
KS ISO 3071 , Textiles — Determination of pH of aqueous extract  
KS ISO 139, Textiles — Standard atmospheres for conditioning and testing  
KS ISO 4913 , Textiles — Cotton fibres — Determination of length (span length) and uniformity index  
KS ISO/TR 11827, Textiles — Composition testing — Identification of fibres  
KS ISO 1833 -11, Textiles — Quantitative chemical analysis — Part 11: Mixtures of certain cellulose fibres with certain 
other fibres (method using sulfur ic acid)  
 
3 Terms and definitions  
For the purposes of this standard, the following definitions shall apply:  
3.1 nep 
 
small knot of entangled fibres (in cotton it usua lly comprises of dead or immature cotton hairs)  
 
4 Requirements   
4.1 Macroscopical  
The fibres shal l be well-carded,  bleached to a good white, free from pieces of thread and reasonably free from leaf, 
shell, fibre , dust and foreign matter.  It may be slightly off white if it is sterilized.  It shall offer appreciable resistance 
when pulled.   
The cotton wool shall be 100 % cotton when tested in accordance with  KS ISO 1833 -11 and  KS ISO/TR 11827 . 
4.2 Microscopical  DKS 508:2023 
vi © KEBS 2023 – All rights reserved  
 Each trichom consist of a single cell about 1 cm to 3 cm in length and 15 to 25 microns in width, forming a flattened 
tubular band with slightly thickened round edges showing from about 50 to 120 twists per cm; the apex is rounded 
and often solid.  
When soaked in iodine water for a few minutes on a filter paper, the trichome assumes a blue colour on adding one 
or two drops of sulphuric acid (66 % v/v). It is soluble, at 20  0C, in sulphuric acid (% v/v), when treated with 
ammoniacal copper oxide solution, the cells swell uniformly without the formation of globular enlargement, and finally 
dissolve, with the exception of the contents of the lumen; it is insoluble in dilute sodium hydroxide solution. It is not 
stained by trinitrophenol solution.  
4.3      Total Viable Count  (TVC)  
The cotton wool s hall be produced under hygienic conditions . If sterile the total viable count  shall be less than 100 
cfu per gram  and if non -sterile, the total viable count  shall be less than 1000 cfu per gram  when tested in 
accordance with  KS ISO 21149 . 
4.4      Length o f staple  
Average length of staple shall be not less than 8 mm. Not more than 25 % by mass of the fibres shall be less than 6 
mm length. This shall be tested in accordance with KS ISO  4913 . 
4.5      Number of neps  
When tested in accordance with Annex A, the neps shall not be more than 700.  
4.6      Submersion time  
When tested in accordan ce with Annex B the time required for complete submersion shall not be more than 10  
seconds . 
4.7      Absorbency  
When tested in accordance with Annex B, the mass of water shall be at least 23 g for each of dry cotton and the total 
mass of 5 g of saturated cotton wool shall be at least 120 g.  
4.8      pH value  
The pH value of the aqueous extract of cotton wool shall range from 6 to 8.  The Ph value shall be tested in 
accordance with KS  ISO 3071 . 
4.9    Soluble substances  
When tested in accordance with Annex C, the water -soluble  substances shall not constitute more than 0.5 % of the 
mass of cotton wool.  
4.10    Substances soluble in ether   
© KEBS 202 3 – All rights reserved  vii 
 When tested in accordance with Annex D, the substances soluble in ether shall not cons titute more than 0.5 % of 
the mass of the cotton wool.  
4.11    Fluorescent brightening agents  
Fluorescent brightening agents shall not be used in the manufacture of cotton wool  ` and  when  tested  in accordance 
with Annex E, no point of fluorescence shall be visible.  
4.12    Oxidizing substances  
No blue colour shall appear on the fibres or in the solution when 1 gram of cotton is immersed in 100 mL of starch 
solution containing 0.5 g of potassium iodine and 0.5 mL of glacial acetic acid.  
4.13    Sulphated ash  
The ash content shall not exceed 0.4 % when tested in accordance with Annex F.  
4.14    Colouring substances  
No bl uish or greenish shade shall be visible when tested in accordance with Annex G.  
4.15    Moisture regain  
The moisture regain shall not exceed 8 % when tested in accordance with Annex H.  
4.16    Net mass  
The net mass of packages shall  not be less than 2.5% o f the declared value.  The net mass shall be determined in 
accordance with Annex J.  
5        Packaging  
5.1      Unit packages  
Each unit shall be   rolled and packed in one lap of uniform width.   The layer shall be compressed so that removal 
of small quanti ties from the cotton shall be met with reasonable resistance.  
5.1.1    non-sterile  packages  
The layer shall be rolled  in strong paper or folded in a wrapper of plastic materials so as to protect the cotton wool 
from dirt or contamination.  
5.1.2    sterile packages  
To maintain sterility, the layer of cotton wool shall be rolled in strong paper and shall also be properly c overed with a 
second wrapper either of strong paper or plastic material.  DKS 508:2023 
viii © KEBS 2023 – All rights reserved  
 5.1.3    Bulk packages  
Several packages of sterile or non -sterile cotton wool shall be packed in polythene or any other suitable wrapper.  
6        Marking  
6.1      Unit packages  
Unit packages shall be clearly and durably marked with the following information:  
a) Manufacturer’s name and/or registered trade mark;  
b) The words “Absorbent Cotton Wool”;  
c) Net mass, in g;  
d) The word ‘Sterilized’ or ‘non-steril ized’ .   
e) country of manufacture ; 
f) Batch number;  
g) Date of manufacture.  
h) expiry date  
i) Storage instructions  
6.2      Bulk packages  
Bulk packages shall be clearly and durably marked with the following information:  
a) Manufacturer’s name and/or registered trade mark;  
b) The word ‘Absorbent Cotton Wool’;  
c) Number of unit packages and net mass of each package.  
d) The word ‘Sterilized’ or ‘non -sterilized’  
 
 
 
 
 
 
 
  
© KEBS 202 3 – All rights reserved  ix 
 Annex  A 
(normative)  
Determination  of number  of neps 
A.1     Principle  
A thin layer of cotton w ool of sp ecified mass is vie wed under transmitted light and count taken of the nu mber of 
neps. 
A.2     Apparatus  
A.2.1    Glass plates  
A.2.2    Transmitted  light  
A.3     Procedure  
A.3.1    A thin layer of cotton w ool wei ghing 0.5  g for an area  of 450 c m2 shall be pl aced betw een two  glass 
plates (A. 2.1). View the thin layer by tr ansmitted light  and c ount the numb er of Ne ps in this area. 
A.3.2    Repeat the proc edure for 4  more sp ecimens. 
A.4     Result  
Report the n umber of Ne ps as the aver age of the 5 r eadings. 
© KEBS 202 3 – All rights reserved  xi 
 Annex B 
(normative)  
Determination  of submersion  time and water absorption  
B.1     Principle  
A specified mass of absorbent cotton wool placed in cylindrical basket is immersed in a tub of water and time taken 
to immerse is measured.  
B.2     Apparatus  
B.2.1  Cylindrical basket, weighing 2.7 ± 0.3 g, of height 80 mm, diameter 50 mm with square openings of 15 mm 
to 20 mm, made of copper wire of 0.4 mm diameter.  
B.2.2     Tub of water , of 10 cm – 20 cm.  
B.2.3     Thermometer  
B.2.4     Stopwatch , 0.2 sec. accuracy.  
B.2.5     Container  
B.2.6     Weighing balance  
B.3     Procedure  
B.3.1  Take random specimen of 5 g of cotton wool from five different places in the package to be examined. Place 
it loosely in the cylindrical basket (B.2.1).  
B.3.2     Weigh the basket using a weighing balance (B.2.6) before placing the specimen.   Weigh again after placing 
the specimen.  
B.3.3     Drop the specimen with its contents in a horizontal position into a tub of water (B.2.2), with water at about  
20 0C reaching a height o f approximately 100 mm.  
B.3.4     Measure by means of stop watch (B.2.4), the time required for the basket to sink below the surface of water 
in sec.  
B.3.5     Repeat the procedure above for two more specimens.  
B.3.6  After testing the submersion time for each specimen, leave the submerged basket at the bottom of the water 
in B.3.4 for 3 min.  Remove the basket with its contents from water.  Leave it for 30 sec in a horizontal position above 
the tub so as to drain the remaining water . 
B.3.7     Place the bas ket in a container (B.2.5) of known weight (M1), weigh it (M2).  
B.4     Calculation  DKS 508:2023 
xii © KEBS 2023 – All rights reserved  
 B.4.1    Immersion time  
Take t he average of the three me asurements in B .3.4 and B.3.5 as  the immersi on time in sec.  
B.4.2   Water  absorption  
B.4.3    Water absorbed 
 
= M2 – (M1 + 2.7 + 5) 
= M2 – (M1 + 7.7) 
 
Where, 
M2    = mass of contain er + basket +  cotton w ool after absorpti on; 
M1   = mass of contain er. 
Water absorbed by each gram of cotton  wool 
 
=𝑊𝑎𝑡𝑒𝑟  𝑎𝑏𝑜𝑟𝑏𝑒𝑑
𝑀𝑎𝑠𝑠  𝑜𝑓 𝑐𝑜𝑡𝑡𝑜𝑛  𝑤𝑜𝑜𝑙 
 
=𝑀2− (𝑀1 + 7.7)
5 
 
 
B.5     Report  
B.5.1    Report the value ca lculated in B.4.1 as the si nking time  in sec.  
B.5.2    Report the value ca lculated B.4.2 as the absor bency. 
© KEBS 202 3 – All rights reserved  xiii 
 Annex  C  
(normative)  
Method for determination of water -soluble  substances  
C.1     Principle  
 
Cotton wool is extr acted in  hot water a nd the extract is dried and t hen we ighed.  
 
C.2     Apparatus  
 
C.2.1    Weighing b alance  
 
C.2.2    Grad uated flask  
 
C.2.3   Burne r  
C.2.4    Funnel  
C.2.5    Filter paper  
 
C.2.6    Drier,  with temperat ure control  
 
C.2.7    Clock  
 
C.3     Procedure  
 
C.3.1   To 5 g of absorbent  cotton, add 500 mL of water  and boil gently  for 30 min, adding  suffici ent water to 
maintain the  original volume.  
 
C.3.2   Pour  the extract  through a funnel  into another  vessel, transf er the cotton  to the funnel  and press out the 
water  absorbed there-in.  With a glass rod, wash the cotton with two 150 portions  of hot water,  press ing the 
cotton after each washing. 
 
C.3.3    Filter  the combined  extracts and washi ngs, evap orate to conc entrate, transf er to the weigh ing bottle  and 
dry at 10 0C to co nstant weight.  Weigh  the resi dual (M) in g.  
 
 
C.4     Calculation  
𝑆𝑜𝑙𝑢𝑏𝑙𝑒  𝑆𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒 =𝑀
5X 100  
                                                                      = 20 M 
                                                           
C.5     Report  
Report the value in C.4 as the percentage of water -soluble  substances.  
 DKS 508:2023 
xiv © KEBS 2023 – All rights reserved  
 Annex D  
(normative ) 
 
Method  for Determination  of Substances  soluble  in ether  
D.1     Principle  
Cotton is extracted in et her and then the  extract is dried and weig hed. 
D.2     Apparatus  
D.2.1    Weighing b alance  
 
D.2.2    Soxhlet  
 
D.2.3    Clock  
 
D.2.4    Drier, with t emperature  control.  
 
D.2.5    Burn er 
 
 
D.3     Procedure  
 
D.3.1   Take approximately 5 g (dry mass) of c otton wool.  
 
D.3.2   Extract  in ether for 4 h by means of a Soxhlet .  The ether shall circulate at the rate of not less than 4 
cycles per hour. 
 
D.3.3   Vapor ize the extract  and dry the rema inder at a temperature  of 100 0C to 105 0C to obtain constant 
mass.  
 
Weigh the r emaind er of the extract ( M) 
 
𝑆𝑜𝑢𝑏𝑙𝑒  𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒 ,𝑝𝑒𝑟 𝑐𝑒𝑛𝑡 =𝑀
5X 100 = 20 M  
D.5     Report  
Report the value the value  in D.4 as the  soluble su bstances in et her in per  cent. 
© KEBS 202 3 – All rights reserved  xv 
 Annex E  
(normative)  
Method for determination of fluorescent  brightening  agents  
 
E.1     Principle  
 
A layer of cotton w ool is e xamined under ultra violet r adiation.  
 
E.2     Apparatus  
 
E.2.1    Ultra-violet light sou rce  
E.2.2    Scale , graduated in mm. 
E.3     Procedure  
Examine a l ayer, about 5  mm in thick ness, under ultra-violet radi ation, of wavelength 3 65 nm. 
 
E.4     Report  
 
The samp le may show only a slight brownish-violet  fluorescence and no point of fluorescence shall be 
visible . 
© KEBS 202 3 – All rights reserved  xvii 
 Annex  F  
(normative ) 
Determination  of sulphated  ash 
 
F.1     Principle  
 
Cotton  is heated and then treated with sulphuric acid and ammonium  carbonate  solution to determine  the 
amount of su lphated ash. 
 
F.2     Apparatus  
 
F.2.1    Burn er 
 
F.2.2    Weighing b alance  
 
F.2.3    Crucible  
 
F.3     Procedure  
 
F.3.1  Take  a samp le of cotton  wool and weigh accurately  to 5 g and then introduce into a previ ously heated 
and cool ed, tarred cr ucible. 
 
F.3.2    Heat cautio usly over a naked f lame and  then to dull r edness at 6 00 0C. 
 
F.3.3    Allow  to cool, add a few drops of ammonium  carbonate  soluti on.  Evapora te and incinerate  carefully, 
allow to cool  and weigh again.  Rep eat the inc inerati on for periods of 5 min to  constant m ass (M). 
 
F.4     Calculation  
 
 
Soleplate ash in % =𝑀
5 X 100 = 20 M  
 
F.5     Report  
 
Report the value ca lculated in F.4 as % sul phated ash. 
© KEBS 202 3 – All rights reserved  xix 
 Annex G  
(normative)  
Method  for determination  of colouring  substances  
 
 
G.1     Principle  
 
Absorbent cotton wool is extracted in ethanol a nd then view ed for any colo uring substances. 
 
G.2     Apparatus  
 
G.2.1    Weighing b alance  
 
G.2.2    Narrow percolator  
 
G.2.3    Cylindrical glass tu be 
 
 
G.3     Procedure  
G.3.1    Extract  10 g of absorbent cotton  in 100 mL of ethanol in a narrow percolator  until 50 mL of the extracts  
are obta ined. 
 
G.3.2  Pour  the liquid into a clean cylindr ical glass tube and test visually  through a 20 cm wide layer on a white 
back ground. 
 
G.4     Report  
 
Report if bluish or green ish shade is observed or not. 
© KEBS 202 3 – All rights reserved  xxi 
 Annex  H  
(normative)  
 
Method for determination of moisture regain  
 
H.1     Principle  
 
A known m ass of absor bent cotton wool is dried and t hen the loss in  mass expr essed as a ratio  of the dry mass.  
 
H.2     Apparatus  
 
H.2.1    Weighing b alance  
 
H.2.2    Drier, with t emperature  control.  
 
H.3     Procedure  
 
 
H.3.1 Weigh  (M1) a known a mount of cotton wool, dry it at a temperat ure of 100  0C to 105 0C until 
constant mass is obta ined.  
 
NOTE The mass is usually regarded as constant if the loss between two successive weighing, taken at an interval of 30 min does not exceed 
0.1 per cent of the first of the two values.  
 
 
H.3.2   Weigh (M 2) again.  This is  the dry mass.  
 
H.4     Calculation  
 
 
𝑀𝑜𝑖𝑠𝑡𝑢𝑟𝑒  𝑟𝑒𝑔𝑎𝑖𝑛 =𝑀1−𝑀2
𝑀2 𝑋 100 
H.5     Report  
 
Report the value ca lculated in H.4  as the moi sture regain in %.DKS 508:2023   
 
© KEBS 2023 – All rights reserved   
 Annex  J  
(normative)  
 
Determination of net mass of package  
 
J.1     Principle  
 
Mass of a p ackage  without  wrappers is tak en on a w eighing balance. This is the  net mass of pack age. 
 
J.2     Apparatus  
 
J.2.1    Weig hting balance, accuracy 1 g. 
 
J.2.2    Measuri ng jar  
 
 
J.3       Procedure  
 
J.3.1    Conditioning  
 
Condition the  specimen  (packa ge) wit hout wr appers in accorda nce with KS ISO 139 . 
 
J.3.2    Take  the conditioned  package  and place it in a measuring jar of known mass. Take  the mass 
of the measur ing jar and its c ontents us ing the  weighing ba lance (J.2. 1). Calcu late the mass of the 
packa ge. 
 
J.4     Report  
 
Report the mass of the p ackage  calculated in  J.2.1 as the net m ass.