what is sandpaper?

StuartMuncerfortheSouthFloridaWoodworkingGuild Page1of10October2015

The Plane Papers

Sandpaper for Woodworking

WHATisSANDPAPER?Sandpaperisdefinedasasheetofpaperorclothwithanabrasivematerialattachedtooneside.Earlysandpaperwasmadewithnaturalmaterials-suchasseashells,sand,orseeds-attachedtopaperwitheitherglueorvarnishandhadarelativelyshortusefullife.Modernsandpaperismadewithman-made,syntheticabrasivesthatareavailableinawidevarietyofproductsthataremoreversatileanddurable.Thereareanumberofpurposesforsandpaper:

t Toremoveamaterialfromasurface-suchasfinishorpaintt Toremovemillmarksandflawsinrawwoodt Toremovesandingmarks-inpreparationfor,ortocompleteafinisht Tomakeasurfacerough-inpreparationforgluet Tomakesmallchangestotheshapeofthesurface

Therearefourcomponentsofsandpaper-thebacking,thebondingagent,theabrasiveparticles,andtheform-eachcontributingtotheuseandfunction-andultimatesuccessofsanding.Whilethebasicsremainthesame,themanufacturersofsandpaperwillcreateuniqueandproprietaryformulasanddesignsforeachcomponenttoimprovetheirproductsandremaincompetitive.

THEBACKINGThebackingusedforsandpaperisasindividualasthetaskthesandpaperwillbeperforming.Thebackingneedstoaccommodatetheheftoflargeabrasiveparticles;stayintactwithwetsanding;withstandintensefrictionheatandpressureofmachinesanders;andflextocontourswhenneeded.PAPERPaperbackingisthemostcommonandmosteconomical.PaperisratedAthroughFbyweight,withAbeingthelightestandFtheheaviest.Lightweightpapers(A-C)aretypicallyusedforhandsanding.Powersanders(disksandsheets)mayuseanyoftheweights.Beltsandersuseonlytheheaviest(E-F)weightpapers.Somelighterweightpapersmaybetreatedwithchemicalstobewaterproofandwillbemarkedappropriately.FIBERFiberbackingismadebyfusingseveralsheetsofpapertogetherbyaprocesscalled"vulcanizing".Theresultisaverystrongpaperbackingusedforfiberorvulcanizeddiscs.Fiberbackingisnottypicallywaterproof.

StuartMuncerfortheSouthFloridaWoodworkingGuild Page2of10

October2015


CLOTHClothbackingisratedbyweight(J,X,Y).TheJclothbackingiscottonwithadegreeofflexibility.TheXclothbackingisaheaviercottonusedforgeneralpurposes.TheYclothbackingismadeofpolyester(upto100%)andbecauseofitsdurability,isusedforheavyduty,highheat,wetsanding,orroughapplications.ThelighterweightJandXclothbackingsmaybetreatedchemicallytobewaterproofandwillbemarkedappropriately.Theheavyweight100%polyesterYclothbackingisnaturallywaterproofandistypicallymarketedaswaterproof.FILMFilmbackingsarelikeaplasticpaper,providingtheflexiblecharacteristicsofpaperwiththestrengthofalightweightcloth.Filmbackingsproducefinerfinishesintheveryfinegritsandcanbeusedwetordry.Filmbackedsandpaperistypicallymuchmoreexpensivethanpaperorclothandmaynotberequiredwithmanywoodworkingprojects.THEBONDINGAGENTThebondingagentistheadhesivethatattachestheabrasiveparticlestothebacking.Therearetwocoatsofadhesiveapplied-thefirsttoattachtheabrasiveparticlestothebacking,andthesecondtoattachtheparticlestoeachother.RESINMostmodernbondingagentsareresinbonds,resistanttotheheatgeneratedbysanding.Resinbondssignificantlyextendtheusefullifeofsandpaper.ANIMALHIDEGLUESomesandpapers,especiallysomeoftheolderandinexpensiveproducts,aremadewithanimalhideglue.Thesesandpaperscanbequicktotearaswellasdeterioratewithfrictionheat,pressure,andmoisture.Thesepapersaremostusefulwithnon-wet,lightfinishingwherelittlefrictionheatisgenerated.THEABRASIVEPARTICLESManyabrasiveparticleshavebeenusedovertheyearssuchassandandglass.Themostcommonlyusedparticlestodayaremanufacturedfromsyntheticmaterials,allowingforextendeduseandalargerrangeofgritsize.Colorwasonceanindicatoroftheabrasivetypebutnowvarywiththeadditionoflubricantsandbythemanufacturertodifferentiateproducts.


October2015


ALUMINUMOXIDE

Description Syntheticmaterial,sharpandblocky,mostcommonforwoodworkingAdvantages Longlasting,durable,economical,abrasiveparticlesfragmentwithheatandpressure

(friability)torenewcuttingedge,sandsfinerwithuse,consistentscratchpatternDisadvantages Unevenscratchpattern,notassharpasgarnetCommonUses Powersanders,rawwood,hardwood,generalusesandpaper

CERAMIC(ALUMINAZIRCONIA)

Description SyntheticmaterialAdvantages Mostdurable,removesmaterialquickly,longlasting-canlast4-6timeslongerthan

othersandpapersDisadvantages Expensive,aggressivegritcaneasilydamagewoodCommonUses Beltsanders

GARNET

Description Naturalmineral,reddishAdvantages Inexpensive,hardsharpedgesfracturewithusetoproducefreshcuttingedges,finish

betterthanaluminumoxide,softscratchpatternDisadvantages Wearsrapidly,poorchoiceforpowersandersCommonUses Rawwood,finishsanding,handsanding,sandingendgrain

SILICONCARBIDE

Description Syntheticmaterial,gray-blackAdvantages Wetsanding,extremelyhardandsharp,cutsquicklywithlightpressureDisadvantages Brittle,wearsquickly,notgoodonbarewoodCommonUses Removingnibsbetweencoatsoffinish,removingoldfinish,wetsanding

THEFORMSandpaperisavailableinanumberofformsandeachformisavailableinanumberofbackings,abrasiveparticles,andgrit.Someofthemostcommonformsareasfollows:

FORM GENERALCOMMENTSSheets

Soldinpacksofmultiplesheets,canbesamegritormultiplegritstofacilitatethesandingprocess,typicallyusedforhandsanding,bestwhenusedwitharigidbacking.

Rolls Soldbylength,samegrit,usedbyorbitalsanders,drumsanders,andhandsanding

Disks Disksattachtoastiffbackingdiscforusewithrotarysanders.Mayuseapressuresensitiveadhesive(PSA)orhook-and-loopmethodforattachment.PSAisonetimeuseonlymakinghook-and-loopdisksmore


October2015


economicalinthelongrun.

Belts Forusewithbeltsanders.Portablebeltsandersuseclothbacking.Beltsshouldbepurchasedasneededastheadhesiveholdingthebelttogethertypicallylastsonlyoneyear.

Specialty Non-standardfootprintforcornersandtightspaces,sandingcords.

FoamBlocks Flexiblethickblocksthatallowsandingofcontours.Keepssurfacerigidforhandsanding.Multiplegritsforremovingpainttofinalsmoothing.Washable.

Sponges Flexiblethinblocksthatreadilyconformtomostshapes.Washable.

SteelWool Notsandpaper.Goodforbuffingbetweencoatsoffinishandsandingcontours.Mayleaveshavingsincracksthatrust.

AbrasivePads Notsandpaper.Goodforbuffingbetweencoatsoffinishandsandingcontours.Willnotrust.

THEGRITGritisdefinedastheaveragenumberofaspecificabrasiveparticleneededtocoverasquareinchofsandpaper.Whentheparticlesarelarge,fewfitintoasquareinchandthegritnumberislow(ie:40-grit).Whentheparticlesaresmall,manyfitintoasquareinchandthegritnumberishigh(ie:320-grit).Sandpaperislabeledwiththegritandgenericgradeasfollows.Note:Thischartisacompositeofmanysourcesandisintendedonlyasanillustration.

GRADE GRITSIZE AVERAGEPARTICLESIZE(µ)Coarse 40-60 269-425Medium 80-120 115-201Fine 150-180 82-100VeryFine 220-240 53-68ExtraFine 280-320 36-52SuperFine ≥360 4-41

CAMIvsFEPAThemajorityofsandpaperismanufacturedineithertheUnitedStatesorEurope.SandpaperfromtheUSisgradedandsizedonascaledevelopedbytheCoatedAbrasivesManufacturers’Institute(CAMI)andapprovedbytheAmericanNationalStandardsInstitute(ANSI).SandpaperfromEuropeisgradedandsizedonascaledevelopedbytheFederationofEuropeanProducersofAbrasives(FEPA)andistypicallynotedbya“P”beforethegritnumber(ie:P320).Asonemayexpect,therearedifferencesbetweenthetwosystems.


October2015


WhencomparingCAMIandFEPAsandpaperfrom60-gritthrough180-grit,theaveragesizeoftheabrasivesparticlesarenearlyequivalentandbotharelikelytodeliversimilarresults.Forexample,a60-gritCAMIwillcomparewelltoaP60-gritFEPA.Whencomparingacrossthe“Finer”grades,theaverageparticlesizebeginstovarysignificantly.Forexample,theaverageparticlesizeof800-gritCAMIisequivalenttoaP1500-gritFEPA.Tocompoundtheissue,FEPArequirestheparticleswithinanygivengrittohaveatightersizerange(standarddeviation)thanCAMIdoes.Forexample,iftheaveragesizeparticleis425µmfor40-gritsandpaper,theCAMIsandpapermayhaveaparticlesizerangefrom400-450,wheretheFEPAsandpapermayhaveatighterparticlesizerangefrom415-435.Itisestimatedthat90-95%ofsandpaperusedtodayisFEPA.OneofthemainreasonsisthatFEPAsandpaperhasaconsistentlyuniformgritinthe80-150-gritrange,thereforecuttingfasterthanequivalentCAMIsandpaper.Inaddition,thetighterparticlesizerangeequatestomoreauniformscratchpattern.WhileithasbeenstatedthatFEPAsandpaperistypicallynotedwitha“P”,thisisnotalwaysthecase.3MwilltypicallylabeltheirFEPAsandpaperwitha“P”.NortondistributesonlyFEPAsandpaper,butitisnotlabeledassuch.KlingspordistributesonlyFEPA,someislabeled,someisnot.MirkadistributesonlyFEPAsandpaperandallislabeledwitha“P”.STEARATED(NON-LOADING)SANDPAPERStearatedsandpaperreferstothosecoveredwithzincstearate(asoap)appliedtothesandpaperandaredesignedspecificallyforusewithresinousorfinishedwood.Woodresinsandfinishesbecomeliquidfromthefrictionheatgeneratedbysanding,coatingtheshavingsgeneratedbythesandingprocess,resultingincloggedsandpaper.Thezincstearatecoatsthemixturetopreventitfromadheringtothesandpaper.CLOSEDCOATSANDPAPERClosedcoatreferstoaproductwheretheabrasiveparticlescover100%ofthebackingwithnospacebetweenparticlestotrapshaving.Finegritsandpaper(greaterthan150)istypicallyclosedcoatwherecloggingislessofanissue-suchasmetal,hardwoods,andfinishedwoodapplications.Withallofthesurfacecoveredwithanabrasiveparticle,aclosedcoatproductprovidesanaggressive,yetconsistentscratchpattern.SEMI-OPEN/OPENCOATSANDPAPERSemi-opencoatreferstoaproductwitha30%reductioninabrasiveparticles,whereasopencoatreferstoa50%reduction.Theparticlesonasemioropencoatproductarespacedfurtherapart(coveringonly40-70%ofthebacking)togivetheshavingsaplacetogoandreduceclogging.Semi-openandopencoatproductsprovidealessaggressiveandcoarsefinishwhencomparedtosimilarclosedcoatgrits.


October2015


CHOOSINGtheRIGHTSANDPAPERSandingisoneoftheleastenjoyableaspectsofawoodworkingproject.Unfortunately,withoutasolidsandingapproach,thehoursinvestedincreatingthe“perfect”projectmayhavebeenwasted.Takingthetimetochoosetherightsandpaper(s)forthejobwillsavetime,money,andfrustrationaswellasproducefinefinishedproject.Thereareanumberofquestionstoaskbeforebeginningasandingproject:

1. Whatistheobjective–areyouremovingpaintorsandingbetweenfinishcoats?2. Howmuchdoyouwanttospend–“skyisthelimit”orfrugal?3. Whataboutsteelwoolandabrasivepads–whencantheybeused?

WHATISTHEOBJECTIVE?Thechartbelowisaguidelinetousewhenchoosingsandpaper.Thegritisthemostimportant.Open,closed,orstearatedcoatwillmakethejobeasierbutisnotmandatoryandmaybemorecostly.Theabrasivemaybelimitedbythemanufacturer,buttheextremes(highandlow)areimportant.

Grit Coat Abrasive

50-6

0

100

-120

150

-180

220

-28

0

320

400

≥600

Ope

nCo

at

ClosedCo

at

Stearated

Garne

tA

lumOxide

Ceram

ic

Silico

nCarbide

BareWood(OpenGrain) x x x x BareWood(FineGrain) x x x x x x x x x BareWood(HighResin) x x x x x x x x x BareWood→ClearCoat x x x x x x x x x BareWood→Stain x x x x x HeavyStockRemoval x x x ModerateStockRemoval x x x x x Shaping x x x x x x Paint/FinishRemoval x x x x x LtPaint/FinishRemoval x x x x x x BeforePrime/Stain/Seal x x x x x AfterPrime/Stain/Seal x x x x x BetweenFinishCoats x x x x x xAfterFinalFinishCoat x x x xWaterBasedFinish x x x x x x xPrepareforGlue x x x x x


October2015


HOWMUCHDOYOUWANTtoSPEND?Theoldadage–“Yougetwhatyoupayfor”isjustastruewithsandpaperasanythingelse.Themanufacturersofsandpapertypicallyprovideavarietyofpricelevelsforconsumers.Atthelocalhardwarestore,a60-gritsheet,from3M,canbepurchasedfor$1.83,$0.87,or$0.66persheet.Whatarethedifferences?

1. For$0.66yougetaluminumoxidesandpaper–nothingmore,nothingless.

2. For$0.87yougetgarnetsandpaperthatfinishesbetterthanaluminumoxide,hasabettergradebackingformoredurability,andisopencoattoreduceclogging.

3. For$1.83yougetaproprietyabrasivesandpaperwithclaimstolast7-15timeslonger,witha

backingthatisslip-resistant,isopencoatandstearatecoatedtoreduceclogging,canbeusedforbothwetanddryapplications,andcanberinsedtoremovebuildup.

Generally,betterqualitysandpaperwillhavethefollowingcharacteristics-

t Willcost2-3timesregularsandpapert Willworkfaster,lastlongert Willhaveastrongerbacking-resistingtearing,addingflexibilityandtheabilitytofoldand

bendtoconformtodifferentshapest Willbemadewithhighqualityabrasivest Willbemadewithresinadhesivesthataddstrength,flexibility,andtheabilitywithstand

temperaturechangest Areopencoatwithastearateoranti-clogcoatingtoreduceclogging.

Withfewexceptions,thepremiumsandpaperswillbethebettervalueinthelongrun.Thatdoesnotmeanthatyouthrowawayyourstashofoldsandpaperoravoidsales.Simplyusethelesserqualitypapersforprojectsthatdonotrequirehighqualitysanding.


October2015


WHATABOUTSTEELWOOLandABRASIVEPADS?Forsomeprojects,steelwooland/orabrasivepadsmaybetheappropriatetool.Manyclaimthatsteelwoolhasafinercutthatresultsinahigherglossfinish,butmayproducerustwithwater-basedfinishes.Abrasivepadsaremoreexpensivebutgoodforsmallprojectsandoddshapesandwillalleviateanyconcernsaboutrust.FollowingisachartfromtheNortonStockAbrasiveProductsCatalogcomparingsteelwoolandabrasivepads.Similarabrasivepadscanbepurchasedfrom3M.

THESANDINGPROCESSThesandingprocesscanbereferredtoas“goingthroughthegrit”.Thisistheprocesswhereyoustartwithacoarsesandpaperandthenstepthroughprogressivelyfinergritstoerasethescratchesmadeinthepreviousstepwithfinerandsmallerscratchesuntiltheyaretoosmalltoseeorfeel.PROCESS1. Startwithcoarsesandpaper,suchas60-grit,toeliminatemajorimperfectionsand/orlevelthe

surface.2. Sandwithprogressivelyfinergrits(80,100,120,150,180,220)toremovethescratchesleftbythe

previouspaper,eventuallyleavingasmoothfinish.


October2015


IMPORTANTNOTESt Ifyoujumpmorethan2gritsizes,suchas60-gritto150-grit,the150-gritwillbeunabletoremove

thescratchpatternmadewiththe60-gritsandpaper.t Sandingpast180-gritmaybeunnecessaryunlesslookingforaglossfinish.Ifaglossfinishis

desired,startwith220-gritandworkupbetweencoatsoffinish.t Ifhandsanding,wrapthesandpaperaroundapaddedblockforbetterresults.t Sandinthedirectionofthegrainasmuchaspossible.t Sandlongerthanyouthinkisnecessarytoremoveimperfections.t Garnet–lastsandingofbarewood.t Toprepareasoftwoodforfinish,stopafter180-grit.t Toprepareahardwoodforfinish,stopafter220-grit.t Ifyouwillbeusingawater-basedfinish,stopafter320-grit.t Alwaysuseasandingpadorbackertosupportthesandpaper.t Sandingfinishesstartsat220-grit–usewet/drysandpaper,steelwool,and/orabrasive

pads.



REFERENCEARTICLES1. BasicsofCoatedAbrasives,klingspor.com2. Sandpaper:ChoosingtheRightSandpaper,construction.about.com3. ChoosetheRightSandpaper,woodworking.about.com4. ProperStepsforEffectiveSanding,3dwoodworkingplans.com5. ChoosingandUsingSandpaper,thisoldhouse.com6. TrueGrit,FineWoodworking,March/April2005,pages116-1177. PremiumSandpaper,Woodsmith,Number221,pages10-118. ACloseLookatSandpaper,Woodsmith,Number190,pages8-99. SandingWithoutSandpaper,Woodsmith,Number152,pages8-910. Sandpaper,FineWoodworking,September/October2013,pages78-8011. WhichBrandsCutFastest…,FineWoodworking,November/December2011,pages40-4312. SandingBasics,FineWoodworking,December2015,pages48-54

WEBSITES1. www.diablotools.com2. www.nortonconsumer.com3. www.3m.com4. www.klingspor.com5. www.mirka.com6. www.shopsmithabrasives.com7. www.gatorfinishing.com8. www.finewoodworking.com9. www.woodsmithlibrary.com10. www.woodworkersjournal.com11. www.en.wikipedia.org/wiki/sandpaper

CATALOGS1. 3M–WoodworkingSolutionsfromStarttoFinish2. Shopsmith–PremiumWoodAbrasives3. Gator-AbrasiveProductsforProsandDIYers4. Norton–StockAbrasiveProducts5. Mirka–EffectiveWoodSanding


The Plane Papers

How to Improve Your Sanding Efficiency Efficincyanding Eff

Sandingcanbealongandtediousprocess.Usesomeofthetipsbelowtospeeduptheprocessandimproveyoursandingefficiency.1. Usetwopowersanders-oneineachhand.2. Connectavacuumtothepowersander.Thesanderridesonathincushionofdustthatprevents

fullcontactbetweenthegritandthewood.Avacuumenhancesdustremoval,thusimprovingsandingefficiency.Onsomesanders,hookinguptoavacuumdoublesthesandingspeed.

3. Skipagrit.Useeveryothergritinsteadofeverygrit.4. Knowwhentostop.Woodslikeoakandwalnuthavecoarsegrainlinesandaroughtexture.So

sandingtoveryfinegritsisawasteoftime.Woodslikemapleandcherryhaveasmoother,moreuniformtexture.Sotheyneedtobesandedwithhighergritsbeforethesandingscratcheswilldisappear.

5. Upgradefroma5-inchpowersandertoa6-inchpowersander.Theextrainchmeansalmost45

percentmoresandpapersurface,plusamorepowerfulmotor.Butbeware;six-inchsandersaretwotothreetimesmoreexpensiveandlittlehardertocontrol.

6. Beforecuttingboards,sandthemallwith80-or100-gritsandpaper.Theinitialsanding,which

removesscratches,dentsandmillingmarks,istheheaviestsanding.Andifyousandboardsbeforecuttingorassembly,youcanusethetoolthatdoesdeepsandingfastest:abeltsander.

7. Usegoodsandpaper.Goodsandpaperhassharperparticlesofgrit,whichbiteintowoodmuch

faster.Premiumpaperremoveswoodattwoorthreetimestherateofstandardpaper.Itcostsabitmore,butthegritstayssharpmuchlonger.

REFERENCES§ HowtoSandWoodFaster,www.familyhandyman.com


The Plane Papers

Sandpaper Grit Chart

AvgParticleSize(µm)↓ CAMI1 FEPA2 Micron Steel

WoolPads

Shap

ing Coarse

268 60 2 269 P60

Medium

201 P80 192 80 180µ

Smoo

thing

162 P100 141 100 150µ 1 ExtraCoarse125 P120 116 120 100µ 0 Coarse

Fine

100 P150 93 150 Medium82 180 80µ 00 78 P180

Finish

ing

VeryFine66 P220 60µ 58.5 P240 53.5 240 Fine

ExtraFine52.2 P280 50µ 46.2 P320 44 280 40µ 000

SuperFine

40.5 P360 36 320 VeryFine35 P400 30.2 P500 28.8 360 30µ 25.8 P600 23.6 400 0000 21.8 P800 19.7 500 20µ 18.3 P1000 16 600 SuperFine15.3 P1200 12.6 P1500 15µ 12.2 800 9µ 10.3 P2000 5µ 9.2 1000 UltraFine

1CAMI CoatedAbrasivesManufacturer’sInstitute2FEPA FederationofEuropeanProducersofAbrasivesREFERENCESt Thistablewascompiledfrominformationfrommanyreferencesitesandisintendedasaguideline

only.


The Plane Papers

Sandpaper – Who Are the Players

Manufacturer WheretoPurchase Website3M

HomeDepot,Lowes,TrueValue,Sears,Amazon,WoodworkersSupply,Grainger,PeachtreeWoodworkingSupply,CraftSuppliesUSA,LeeValley

3M.comOnlinecatalogpdfcatalogiphoneapplication

Diablo

HomeDepot,Amazon,PeachtreeWoodworkingSupply

diablotools.comOnlinecatalog

Gator

Lowes,TrueValue,Amazon

gatorfinishing.compdfcatalog

Klingspor

Woodworkinghop.com,Amazon,WoodworkersSupply,Sears,Woodcraft

klingspor.comOnlinecatalog

Mirka

Mirka-online.com,Amazon,WoodworkersSupply,PeachtreeWoodworkingSupply,Woodcraft,Rockler

Mirka.compdfcatalog

Norton

Amazon,Grainger,Sears,PeachtreeWoodworkingSupply,CraftSuppliesUSA,Woodcraft,LeeValley,Rockler

nortonconsumer.compdfcatalog

Shopsmith

Lowes,Amazon,PeachtreeWoodworkingSupply,

shopsmithabrasives.compdfcatalog

what is sandpaper?

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