Ink Making Experiment – Boiling Water

Well, that was informative.

The experiment below was not done with chemistry labratory scientific rigor. Not what I do. And it was a first time exploratory experiment to gather observations so that more specific and perhaps precise experiments in the future. In other words, this is, “I wonder what happens when” kind of experiment.

Many recipes for making european iron gall ink tell the reader to use “an earthen vessel” of some kind or another. Or to use “an unglazed pot” of some kind or another.

Today in the USA that isn’t so easy to do. Basically think bisqueware. Dried, maybe fired but not glazed clay pots and/or containers. First of all they aren’t easy to find. And when you do find them or find someone willing to make one, the price is not inexpensive. And rightly so I’m sure.

So how about those fired unglazed pots for holding flowers and herbs and the like? Yeah, they tend to come with a hold in the bottom for drainage. However, I was finally able to locate some that didn’t have the hole in the bottom. And today I experimented with one.

Experimental Question: How does boiling in this thing work?

Hypothesis 1: The earthen vessel will break due to heat extremes.

Hypothesis 2: The earthen vessel will seep water due to being porous.

Methods/Procedure used:

Grab the earthen vessel fill it with water about 2/3 of the way up. Turn on the electric stove. Dump water out into a measuring cup to find out how much water I am starting with. 250 ml. I couldn’t do that again if I had to. But I did it this morning. Pour the water back into the earthen vessel. Put it on the heating element that has been turned on.

I did not actually time how long it took to boil becuase right now, proof of concept and wanting to watch the thing carefully.


Yes, seepage occured. Areas at the water level and below changed color to a wet color and touch confirmed that in fact the earthen vessel was wet on the outside due to known seepage through the porous clay material. And slightly above it as the porous material whicked water up some as well.

By general observation it seemed take much longer to boil than the same amount of water would have taken in a modern metal pot.

Steam. Lots of steam. Interestingly the pool of water in the pot steamed not very much. The steam eminated from the water that had whicked up the earthen vessel.

Later the outside of the earthen vessels started steaming. Yes, it steamed in rings around the earthen vessel on the outside.

Eventually the water in the earthen vessel began to boil. It quickly went from small bubbles forming on the bottom the earthen vessel to full boil.

After one minute of a full boil I took it off the heating element using regular kitchen tongs. Poured the water back into the same measuring cup. Volume of water? 150 ml. That is a significant loss of water. Much more than typically lost in a metal pot.

The earthen vessel did not initially seem to have broken. However, now that the earthen vessel had dried and it is more than 8 hours later, three cracks were observed that previously hasn’t been there.


Hypothesis 1: Proven.

Hypothesis 2: Proven.

Such a first experiment creates many observations and allows new questions to be asked while answering very few.

What happens if I add vinegar, wine or beer to boil?

What happens if I put something in the water? Like Oak galls for extracting gallo-tannic acid?

Is this why recipes say, “After it comes to a boil, when it reduces by a couple of fingers…” Because if you said that before it boiled, you’d never get to a boil?

Anyway, that’s the ink experiment for the day. So far, the difference between boiling in a modern pot and a earthen one are not small. And I wonder how making ink in a earthen vessel will change things.

4 responses to “Ink Making Experiment – Boiling Water

  1. Nice article. I use donaubies [mis-spelled] which are Japanese cooking pots. I’ve used them on my gas stove burners & my propane camp stoves, too. I’m wondering if these would work w/out getting liquid/water into the ink. Next time I’m in Little Tokyo, I’ll find a small, inexpensive one, give it a go & let you know what happened. Cheers/Thankx

    • Please do. I have period recipe resources for Iron Gall Ink making here on my blog. After this experiment I wonder if the reaso the period recipes use large quantities of copperas and galls and gum arabic is that the unglazed earthen vessel absorbs so much of it leaving behind far less than what was put into it. This would also explain why the recipes want you to use a new earthen vessel each time. A used earthen vessel will put some stuff back into the new batch and that can make things different. So kind of a quality control method.

  2. Surely it wouldn’t be difficult to find a potter to make an earthenware vessel to your specifications. We are legion.
    Nonetheless, well done experiment, thanks for sharing. Wish I could see it in person.

    • Indeed you are legion. đŸ™‚

      The problem is affording your good work and any shipping needed. The recipes call for “a new” earthen vessel so essentially it is a one use item. So paying what it is worth tends to not be affordable to me. But the work involved to make it is certainly worth the price being charged. As an artist I’m not going to ask another artists to lower their reasonable prices.

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