Since Soemarko's LC-1 is out, I would suggest starting with a bottle of HC-110. A 1:99 dilution of the syrup is a good starting point. For easy measurement, I suggest making a 1:4 stock solution that is 400 mL water and 100 mL syrup. To make a liter of 1:99 working solution, pour 50 mL of the stock solution in to a one liter graduate. Then fill the graduate to the one liter mark and mix. I'd try dilutions from 1:49 to 1:199 to alter conrast. The lower the amount of syrup, the lower the contrast. To make 1:49 working solution, use 100 mL of stock, then fill to the one liter mark. To make 1:199 working solution, use 25 mL of stock, then fill to the mark.