I dissolve about 1 gram per ml in 95% ethanol for longer shelf life, then pour a bit more than a tablespoon of that into 500ml of clean water to use as the mouthwash. I've been doing this for five or six years, so I have developed an intuition for the concentration I am looking for based on how the solution looks in the bottle, so I'm doing this dilution by eye and not measuring precisely, since I am not ingesting the dye in this case anyway. The concentration I am looking for is very blue, but its about the minimum concentration that will stain the bacterial films in my mouth. It doesn't leave a strong blue stain on my tongue, but it does really show where I missed a spot brushing. If I spill it on my skin the stain is gone in the morning, and the mouthwash does not stain my porcelain sink.Thank you for that. What is your dilution for mouthwash? Is it clear?
For a sore throat I use a somewhat stronger concentration, gargle, and spend a few minutes with a 660nm flashlight in my mouth.
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