manygas bubbleholesappears to be, aftercleaning,the most contaminated
material of thosehaving beeninserted in the floor of a cheese-processingsite.
Furthermore, a significantlinearcorrelationwas observed between the number
of spherical holes and the cleanability as assessed by a laboratory test.
Masurovskyand Jordan (1958)and Holahand Thorpe(1990)havealso observed
that surfaceswhichat first glanceappeared to havea readily cleanable,smooth
surfacebut were,however, verydifficult to clean,werepreciselycharacterised
by the presenceof smallholes whensurfaces wereexamined in moredetail.
Thesecrevices do not give any slip resistance and are thereforeveryundesirable.
Theeasiestwayto detectsucha defectis to observethe materialundera
stereomicroscope(Fig. 9.3) at40 magnification.The observationallowsalso
seeingcracksoften foundaround aggregates, holesleft by removed aggregates,
spongy' aggregates,verydeepcrevices and other texture defaults.Underthe stereomicroscope,it is also interestingto test witha simplemetallic pointthe anchorageof the aggregates. If theyare easilyremovedby manualhandlingof the metallicpoint,it meansthat theywill be easilyremovedwhensubjectedto thein-house' mechanicalstresses. Suchflooring will not maintain theirslip
resistance and will be difficult to clean.Around 50%of the flooringmaterials
(resin-basedor ceramic tiles)receivedat our laboratorypresented suchobvious
texture defaults visible underthe stereomicroscope.Unfortunately, observations
are not measurements and in some case, theremay be some difficultyin
interpretation. In order to rejector accept a flooring material for a food
processing area,it is proposed that the observationshould be doneby at least
threetrainedpersons,whoshouldall reach the sameconclusion.
Roughness measurement at the microscopiclevel couldbe a wayto further
characterise material cleanability. Mettler and Carpentier (1999) explored
Fig. 9.2 Cross-sectionof a resin-basedflooringmaterialshowinggas bubbleholes.Improving the design of floors 175