Tinfoil is fine.

In AE it is more commonly called aluminum foil. But tin foil would be understood.

Auch in England hört man öfter al(uminium) foil

Ja, aber sie fragt, ob es 'aluminium foil' sein MUSS, und das muss es nicht. Wie gesagt, tin foil is fine, we use it all the time. Doesn't mean there's anything wrong with aluminium foil (apart from the fact that it's a lot more difficult to spell... ;))

thats exactly why i was asking, except that im not female ;)

In fact, just 'foil' alone is fine: wrap in foil, line baking pan with foil, etc. In AE more specifically 'aluminum foil,' but it's usually not necessary to specify.

(Remember that Frischhaltefolie is not called 'foil,' but 'plastic wrap,' and all other kinds of Folie made from plastic are usually translated as film, sheeting, overhead transparencies, etc., but generally not foil. 'Foil' in English usually means made out of something metallic.)

Tinfoil is theoreticaly okay but in AE is actually used mainly only for decorative or figurative senses, suggesting, say, cheap glitz.

theoretically

sorry, me - sexist that I am, I automatically assumed that cooking questions had be asked by a female. Shame on me.

(And just for completeness's sake: Frischhaltefolie in BE would be cling film.)

had to be asked

@ #5: Why don't you sign as:

me - Tarzan

and (if need be), add:

you - Jane . . .