fermenting Dumb question for the fermenting gurus

[Jeff H]

How is the % of salt calculated for a ferment? I keep hearing 2.5%, 4%, 6% and others, but no one says how this is calculated.
 
By weight?
By volume?
 
Just thinking volume here, if I have a 1 quart container which is 64 Tbsp of liquid, a 4% salt mixture would be 2.56 Tbsp of salt. That seems high to me, but if it is the correct way to calculate it, I guess it is what it is.

 

[beerbreath81]

From my experiance that seems like the right amount
 
From Sandor Katz--
The strength of brine varies widely in different traditions and recipe books. Brine strength is most often expressed as weight of salt as a percentage of weight of solution, though sometimes as weight of salt as a percentage of volume of solution. Since in most home kitchens we are generally dealing with volumes rather than weights, the following guideline can help readers gauge brine strength: Added to 1 quart of water, each tablespoon of sea salt (weighing about .6 ounce) adds 1.8% brine. So 2 tablespoons of salt in 1 quart of water yields a 3.6% brine, 3 tablespoons yields 5.4%, and so on. In the metric system, each 15 milliliters of salt (weighing 17 grams) added to 1 liter of water yields 1.8% brine

 

[poypoyking]

I go by weight by Sandor Katz' guidelines, which is roughly 3 tablespoons per 5 lbs of vegetables (not sure what actual percentage that is).  You can go more or less, but I tend to go a little less.  For 1lb of peppers/mash I use 2 teaspoons of salt.  One pound of peppers fills a quart jar about 2/3 full for me.

 

[Heisenberg]

I use 3.6% (w/v) which would be 36g salt/1000ml of water.  I dont base it at all on the weight of the peppers.  One thing to remember though is that the addition of a salt solution will actually draw water out of a vegetable (hypertonic solution), so the brine will get further diluted.  But even if it dilutes out to a final concentration of 2%w/v, thats still high enough to suppress the growth of most nasties.