I inadvertently posted this article under the vacuum filtration thread and it got buried, If the moderator will allow, I will post again as a separate thread and may have to split it into two . Here goes:
Several posts in different threads have asked the question what level of vacuum should you draw either as you rack/transfer your wine from one glass carboy to another and thereby degas the wine further, it or as you vacuum fill your wine bottles.
A couple of considerations: one is the integrity of the glass carboys, and the level of the wine in the carboys. My approach to date is to max the vacuum draw, which for my pump is 27 in Hg, or about .52 psi absolute ( 14.7 - .52 relative) . This is a lot of vacuum and I suspect my gauge may be misreading although I have no easy way to check it. No effects so far on the glass carboys, but it certainly does a number on the plastic ones. I feel a lot safer using the carboys that have the extra ridges running vertically ( have a green tint to them).
The second consideration is the effect on the dissolved CO2, and the ethanol, that is is solution. I have noticed that if I add small stainless steel screws, to the bottom of the receiving wine, I will get much more Carbon dioxide release at lower vaccum levels than without. My guess is they are nucleation sites for the CO2 coming out of solution. More importantly tho' is the effect of very strong vacuum on alcohol in solution. I finally found a boiling point versus atmosphere table for ethanol (ethanol producers database). This table shows that at 19.7 deg C, and a vacuum of 2.13 in Hg, ethanol will boil/convert to a gaseous state. ( Part Two follows)
Several posts in different threads have asked the question what level of vacuum should you draw either as you rack/transfer your wine from one glass carboy to another and thereby degas the wine further, it or as you vacuum fill your wine bottles.
A couple of considerations: one is the integrity of the glass carboys, and the level of the wine in the carboys. My approach to date is to max the vacuum draw, which for my pump is 27 in Hg, or about .52 psi absolute ( 14.7 - .52 relative) . This is a lot of vacuum and I suspect my gauge may be misreading although I have no easy way to check it. No effects so far on the glass carboys, but it certainly does a number on the plastic ones. I feel a lot safer using the carboys that have the extra ridges running vertically ( have a green tint to them).
The second consideration is the effect on the dissolved CO2, and the ethanol, that is is solution. I have noticed that if I add small stainless steel screws, to the bottom of the receiving wine, I will get much more Carbon dioxide release at lower vaccum levels than without. My guess is they are nucleation sites for the CO2 coming out of solution. More importantly tho' is the effect of very strong vacuum on alcohol in solution. I finally found a boiling point versus atmosphere table for ethanol (ethanol producers database). This table shows that at 19.7 deg C, and a vacuum of 2.13 in Hg, ethanol will boil/convert to a gaseous state. ( Part Two follows)
