On food and cooking the science and lore of the kitchen ( PDFDrive ) 1482
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unlesstheyessentiallydehydratethem,since
thefoodsurfacegetsnowarmerthanthe
interior.Thin,radiation-concentratingmetal
sheetsinspecialmicrowavablefood
packagingcanhelpheatthefoodsurfaceto
thepointthatitbrowns.
UtensilMaterials
Finally,abriefdiscussionofthematerials
fromwhichwemakeourpotsandpans.We
generallywanttwobasicpropertiesina
utensil.Itssurfaceshouldbechemically
unreactivesothatitwon’tchangethetasteor
edibilityoffood.Anditshouldconductheat
evenlyandefficiently,sothatlocalhotspots
won’tdevelopandburnthecontents.No
singlematerialprovidesbothproperties.
TheDifferentBehaviors
ofMetalsandCeramics
Aswe’veseen,heatconductioninasolid
proceedseitherbythemovementofenergetic
electrons,orbyvibrationincrystalstructures.
Amaterialwhoseelectronsaremobileenough
toconductheatwellisalsolikelytogiveup
thoseelectronstootheratomsatitssurface:
inotherwords,goodconductorslikemetals
areusuallychemicallyreactive.Bythesame
token,inertcompoundsarepoorconductors.
Ceramicsarestable,unreactivemixturesof
compounds(magnesiumandaluminum
oxides,silicondioxide)whosecovalentbonds
holdelectronstightly.Theythereforetransmit
heatslowlybymeansofinefficientvibrations.
Ifsubjectedtothedirectandintenseheatof
thestovetop,ceramicscan’tdistributethe
energyevenly.Hotareasexpandwhilecooler
areasdonot,mechanicalstressesbuildup,
andtheutensilcracksorshatters.Thisiswhy
ceramicsaregenerallyusedonlyintheoven,
wheretheyencounteronlymoderateand
diffuseheat,orareappliedinthincoatingson
