Context: In ultra high vacuum systems, some very "odd" leakage paths and outgassing sources must be considered. The water absorption of aluminium and palladium becomes an unacceptable source of outgassing, and even the adsorptivity of hard metals such as stainless steel or titanium must be considered. Some oils and greases will boil off in extreme vacuums. The permeability of the metallic chamber walls may have to be considered, and the grain direction of the metallic flanges should be parallel to the flange face.

Question: What can boil away in extreme vaccum exposure?
Answer: Some oils and greases

Question: How should the grain direct of metallic flanges run to flange faces?
Answer: parallel

Question: What are 2 metals that can be absorbed in an ultra high vacuum system?
Answer: stainless steel or titanium

Question: What becomes a concern in an ultra high vacuum system regarding aluminum or palladium?
Answer: water absorption

Question: What will boil off when aluminum absorbs water?
Answer: Unanswerable

Question: How should palladium be placed when it has oil on it?
Answer: Unanswerable

Question: What are two metals that can be absorbed in an metallic flange?
Answer: Unanswerable

Question: In what area will water boil off?
Answer: Unanswerable

Question: What will grease usually run parallel to?
Answer: Unanswerable