found an article after I asked for help, which suggests 10oz of salt to 1 gallon/3.78 ltrs of water, and you're to brine for an hour per pound/450g, so I'm not going to need that much, so I reckon about a litre of water to 70g of salt, and brine the thighs for about 4 hours, maybe less depending on the weight, going to be using common table salt, more of it, and it's cheaper...
found an article after I asked for help, which suggests 10oz of salt to 1 gallon/3.78 ltrs of water, and you're to brine for an hour per pound/450g, so I'm not going to need that much, so I reckon about a litre of water to 70g of salt, and brine the thighs for about 4 hours, maybe less depending on the weight, going to be using common table salt, more of it, and it's cheaper...