The instructions for the API KH test say to count the drops until the sample turns "bright yellow." Seems a bit vague -- how do they define BRIGHT yellow? There is no color comparison card chart provided.
My test sample is a very pale/light yellow after the 1st drop. I can keep on adding drops to make it more yellow, but then I don't know when I've reached bright yellow -- seems very imprecise.
My test sample is a very pale/light yellow after the 1st drop. I can keep on adding drops to make it more yellow, but then I don't know when I've reached bright yellow -- seems very imprecise.