My recipe doesn't make exactly 4 oz -
I have a scale that weighs to .1 gram.
I put a glass cooking pot on the scale and tare it to 0
I put in the distilled water. I note the weight of the distilled water.
I multiply that by 28% == this tells me how much water I have to remove from the pot. I subtract that amount from the weight of the water. (conversely, you can multiply it by 72% and it will give you the same figure as when you have subtracted the 28% from the original amount)
I carefully remove water until the water left in the pan is the original weight LESS the 28%.
I then add the SC until I get back to the original weight. (add the last little bit very carefully - sometimes the weight jumps if the flake is of any size)
This is the way I was trained in the MOH training - and it will work for any amount - big or small - the disadvantage is that you can't get an exact amount.
Steve has a chart on his website at Keavy's corner for how to do it to get specific amounts.
keavyscorner.com/index.php?main_page=page&id=8&chapter=10