6

At https://www.catsfork.com/CatsKitchen/lime-water I see a technique from a cookbook called Nourishing Traditions for soaking cornmeal in 'lime water', created from pickling lime (calcium hydroxide, aka "cal"). The technique starts by preparing a quart of lime water by adding a quart of filtered water to something like a half a cup of pickling lime powder, sharing, letting the powder settle out, and then using the water obtained by pouring the liquid portion off of the settled solids.

I am confused because according to the solubility table at https://en.m.wikipedia.org/wiki/Solubility_table, something like 2 grams of calcium hydroxide would be expected to dissolve in a quart of water. That's basically one mL of calcium hydroxide that is expected to dissolve; why would you use a half cup (which is approximately a hundred times that amount)?

Am I missing something about the technique? Is there a reason why using a dramatic surplus might be anything other than wasteful?

1 Answer 1

5

The supersaturation of cal seems to be the common instruction in most online sources, but no reason is given. The best reason seems to come from chemistry texts, which note:

Ca(OH)2 is only slightly soluble in water (0.16g Ca(OH)2/100g water at 20°C) forming a basic solution called lime water. The solubility decreases with increasing temperature. The suspension of calcium hydroxide particles in water is called milk of lime.

According to Cook's Illustrated, you are trying to get as much lime into the water as you can, since your target is an extremely alkaline (pH 12.4) solution. So .. if it's hard to dissolve Ca(OH)2, and you're going for maximum saturation, dump a whole bunch in and pour off the solution.

2
  • This is great -- thank you so much for the references! I guess starting with very cold water would also help.
    – Bosh
    Aug 27, 2020 at 19:29
  • 3
    Some of your Ca(OH)2 is going to react with carbonates already in your water and form Calcium Carbonate - CaCO3. It's not very soluble stuff: en.wikipedia.org/wiki/Calcium_carbonate so at least a slight excess of Ca(OH)2 is needed to maximize soluble calcium. Aug 27, 2020 at 22:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.