This is another question I'm curious about. The way I understand it (?) the Campden tablet does two things- It creates (probably have this one wrong) CO2 like the fermation process and so fills up the air gap in the bottle, and it prevents oxigen in the wine from binding with it from racking. A third thing I've been told (again, probably wrong?) is that it kills off bacteria in the wine as well.
Anyway, if the campden prevents oxygen from binding with the wine then is it better to add it to the wine minutes before racking? Or, if it does also create CO2 then am I better off adding it to the wine minutes AFTER it's been racked?
I've only got one carboy at this time so I have to siphone the wine into my primary bucket, clean the carboy and get rid of the sediment, and then siphon the wine back into the carboy. I've been waiting until it's moved back into the carboy before adding the campden. Which is right, before or after moving the wine, and why is it the right thing to do?
Also, I've asked this in another thread but might as well ask here too. I'm brewing 6.5 gallons of pear wine. In the primary is it 1 tablet per gallon? And in the secondary when racking how many tablets should I use each time? I only put 3 into the primary and have been putting one tablet in at each racking after it has been racked. I know some of you guys prefer powder but I'm early into this wine making thing and just bought the tablets to make things nice and easy as far as measuring goes.