25 Campden Tablets ~1/2 ounce. Use to kill off bacteria and yeasts.
two crushed tablets equal 1/4 teaspoon.
1 gram of metabisulfite ( 1/4 teaspoon ) per gallon = 150 ppm
1 Campden tablet per gallon = 30 to 50 ppm
Campden tablets typically contain 0.44 g each of sodium metabisulfite (plus filler) and 10 of these are equivalent to one level teaspoon (5 mL) of sodium metabisulfite
Add one tablet to each gallon of ferment (must / wort/ sugar and tea) 24 hour prior to adding the yeast – before the fermentation.
Crushed and dissolve in a small amount of water. Then stirred thoroughly into the rest of the batch.
The metabisulfite dissipates into a gas. Trapped it serves as a disinfectant. left open it dissipates into the air usually within 24 hours.
Brewers use this as it sterilizes or kills off most everything. Yet leaves the batch ready to ferment fresh. Your bacteria and yeasts = introduced AFTER the Campden has dissipated , is free to inoculate the batch without competition.
Chlorine or chloramine
One tablet will eliminate chlorine or chloramine in 20 gallons of water.. note Chlorine and Chloramine may leave a medicinal taste in your brew. Chlorine is easily removed by boiling, but not Chloramine. but some sources say Chloramine can be removed by Campden Tablets, Ultraviolet light, Ascorbic Acid and sodium ascorbate (Vitamin C) 1 mg per 10 gallons. Vitamin C is good overall for most ferments. (note: some say this may add more ammonia ) Activated Carbon is also effective but takes a long contact time. A commercial product available at Pet Stores is Amquel which is sodium hydroxymethanesulfonate. The chemical used in most similar products is sodium thiosulfate. Used to make water safe for your fish in your aquarium.
Often we find we only need to work with one gallon and cutting up one tablet into 20 pieces is impossible. So what we do is to dissolve one tablet in 20 ounces of water. Then when we need to de-chlorinate on egallon we use ounce form our 20 oz bottle.
As a sanitizing solution crush up 4 tablets into a quart of water. This can be used as a sanitizing rinse, or you can pour it into a fermentation container and allow the fumes to sanitize the entire insides.
Add one table per gallon just before bottling. This achieves two things: 1. traps oxygen and stops oxidation (changing flavors) and 2. stuns the yeasts. Giving time to Chill your brew.