Pressure and Vacuum: High	 pressure	 facilitates	 infiltration	 of	 dense	 specimens	 with	
viscous	resinous	embedding	media	at	the	block	forming	stage,	but	is	rarely	employed	for	
biological	specimens.Tissues,	 particularly	 lung,	 are	 de-aerated,	 and	 the	
solvent	 boiling	 point	 is	 reduced,	 thus	 facilitating	 evaporation	 of	 the	 reagent	 from	 the	
molten	infiltration	medium.Vacuum	 applied	 during	 dehydration,	 clearing	 and	 infiltration	 stages	
improves	 the	 quality	 of	 processing.Positive	pressures	for	fluid	transfer	that	are	encountered	in	closed	
system	 processors	 are	 probably	 too	 low	 to	 have	 a	 significant	 influence	 on	 tissue	
infiltration. 2005).