The Power Of Dilution

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Dilution is a quick way to get something quite clean, if you're not worried about absolute cleanliness.

It's easily shown with a little bit of data.

Pitcher and rag, dry

For the example in case, I was using an old washcloth rag as I touched up the outside of my house with caulk. It's a water-based caulk which readily rinses off.

I used an old pitcher with some 5" of water in it, as a wash basin. Whenever the rag got fairly gunky, I'd drop it in the pitcher and knead out the caulk. This also rinsed my hands.

At first I only did one rinse: Fill the pitcher with fresh water, drop the rag in it, knead out the caulk, and dump out the water and do more caulking. But I found that my hands were getting a little sticky after a few hours of work; there was still a bit of caulk left after that rinse.

Then I started rinsing twice and my hands felt much cleaner.

How much difference did that extra rinse make?

A Demonstration of Dilution

Pitcher and rag with about 4" of water

I used an old pitcher and rag. I weighed them when completely dry, then with a typical 5" or so of water (for caulk rinsing), then I dumped the water and wrung out the rag and weighed them again (water residual). This was a quick dump of water (one second fling) and a two-second squeeze of the rag... I'm not trying to test how dry I could get them. Quite the opposite: How much dilution do you get when you are keeping moving fast while doing a job? I'm testing the worst case dilution scenario; in other words, it would only be better if you wrung your stuff better.

Data

Pitcher and rag, completely dry: 195.0 grams
Pitcher and rag with about 4" of water: 891 grams
Pitcher and rag after dumping water and squeezing rag a couple of seconds: 235.2 grams

Calculations

Pitcher and rag, water dumped and rag wrung
Net total of water (full - dry): 696 grams (24.5 ounces)
Net water residual (wrung - dry): 40.2 grams
Percent water left: 5.78%
Inverse (1/.0578): 1 in 17.3

Extrapolation

Let's say 5% of the original water is left, to make calculations easy. This is just a power calculation (0.05n); calc different percents yourself, if you want.

Rinse Percent Left 1 in
1 5.000000% 20
2 0.250000% 400
3 0.012500% 8,000
4 0.000625% 160,000
5 0.000031% 3,200,000
Scales, FWIW

Demonstrated

It's easy to see why the second rinse made a big difference. A third rinse would probably not make an appreciable improvement in my situation if you already only have 1 in 400 parts (a quarter of one percent) of the original liquid left, as of the second rinse. But for your purposes, you may want more.

Dilution is a simple and reliable strategy for removing impurities quickly.