January 12, 2016

Baking with Wood Ash? (Part 2)

In Part One I asked the question, "Can I somehow use hardwood ash as a substitute for baking soda?" We looked at the history of baking soda, including it's early precursors made from hardwood ashes. The earliest recipes refer to the somewhat refined products of potash and pearlash. But how would that equate to sifted hardwood ash? Unknown. The chemical composition of hardwood ash is highly variable, depending on tree type and burning temperature. Still, for a little kitchen chemistry experiment, I figured I'd just have a go and see what I got.

To test my ashes, I made ash water by stirring the ashes into one-quarter cup of filtered water and letting it sit overnight.

Making ash water with hardwood ashes collected from the wood stove.

I made three solutions: one with one tablespoon of wood ash, one with two, and the last with three tablespoons. These were stirred into 1/4 cup filtered tap water. The insoluble components sank to the bottom and the next day I poured off the clear water containing the soluble components that I wanted.

My first step was to test each of these with litmus paper.

Left to right: 1 tbsp, 2 tbsp, and 3 tbsp.
I judged the results to be 10, 11, & 12

This kind of pH testing is approximate but still helpful. As you can see in the caption, I found the solutions to be progressively more alkaline.

The next step was to see how each of these would react with an acid - in this case white vinegar. I started with a "control" of 1 tablespoon baking soda in 1/4 cup vinegar.

My control - reaction was immediate.

For my test subjects I used one-quarter cup vinegar and 1 tablespoon of ash water. Here are my results.

Solution #1 (with 1 tbsp wood ash) - no reaction.

Solution #2 (with 2 tbsp wood ash) - no reaction.

Solution #3 (with 3 tbsp wood ash) - no reaction.

Surprised, I dumped the remains of solution #3 into the vinegar and, again, no reaction. I had been expecting at least some reaction so I was puzzled. I did one more vinegar experiment, this time adding 1 tablespoon dry hardwood ash.

Solution #4 - wood ash in white vinegar - reaction. 

The reaction was not as vigorous as the control, but it was a fair one nonetheless. The murky color, however, doesn't seem to recommend straight wood ash for baking, does it? Still, it got me pondering.

Now, I have to mention that chemistry was my worst subject in both high school and university. That being said, my conclusion was that somehow, combining the ash water and vinegar did not produce carbon dioxide gas, which is needed to make baked good rise. My theory was confirmed in a comment in Part 1 by Jake from The Homestead Laboratory (if you haven't visited his blog, by all means do. Lot's of really good stuff there.) He wrote:
"Passing water through wood ashes extracts both potassium carbonate and potassium hydroxide (and other potassium salts, and the sodium salts, too, but there's fewer of those). I don't think most articles consider that there is a significant amount of potassium hydroxide, but that's what reacts with carbon dioxide to make potassium bicarbonate. Potassium carbonate wouldn't react with carbon dioxide; it's already "fully carbonated." :-)"
Potassium carbonate is pearlash, which I mentioned in Part 1. The lack of reaction would explain why the historical recipes I've seen do not call for an accompanying acid. The reaction must therefore be heat activated.

So my preliminary experiments did not turn out as I expected, and left me wondering about those references to ash water I told you about in Part 1. What's next? This post is probably long enough, so I'll answer that in Part 3. Click here to continue.

Now available: How To Bake Without Baking Powder: modern and historical alternatives for light and tasty baked goods. Includes 54 non-baking powder recipes. Click here for more information and where to buy.

37 comments:

kymber said...

and this is why people love reading your blog...you ARE a chemist in the word's literal meaning...and i will keep checking back until you figure this out. thanks for all of your experiments Leigh! we appreciate them!

sending much love! your friend,
kymber

Kris said...

Wowser. Great experiment. So much old knowledge lost, it can't be recovered on re-discovered. You go gal. I'm on the edge of my seat ... can't wait for Part III!

Renee Nefe said...

you should be able to make soap with it. ;)

Penelope White said...

Try a small loaf of bread.....

Leigh said...

I'm already thinking that the "modern" invention of baking soda is as good as it gets. :) Still, understanding this and having options available do much to increase my feeling of preparedness. :)

Leigh said...

I confess that sometimes I have the feeling of "what have I gotten myself into!" LOL

Leigh said...

That's so true. I have directions for making woodash lye. When it floats an egg it's said to be strong enough. :)

Leigh said...

I'm thinking biscuits!

Sunnybrook Farm said...

They used to use salt to make salt risin bread, basically it is fermenting a potato or something and using the bacteria like yeast. Probably nicer than wood ash.

Farmer Barb said...

Wow. You know when you put soil in vinegar to see if it fizzes, must be the same...

Chris said...

Interesting hypothesis all round. Heat would be the next logical conclusion. Though I can't help wonder if its something in a recipes ingredients which makes it react more.

Given that baking soda is dry, it's more condensed. Adding it to vinegar therefore, creates an immediate reaction. Yet you were adding liquid ash water to liquid vinegar. Perhaps it needs density to create lift, like the baking soda - only the density is the dry ingredients?

I'm only forming my own hypothesis mind you. ;)

deborah harvey said...

leigh,
here's something i read long years ago.
split orncobs in half and dry in oven. scrape out the dried cores and use for baking powder.
cannot remember if anything was to be added to the ash. it isn't burned, just dried, if memory serves.

PioneerPreppy said...

Did you think about using the wood ash as a soak rather than mixing it in with the water? Putting in a tea holder or cheese cloth bag and letting it soak in? With the right micron size filter you could maybe just let the elements in that you are wanting.

Then again I took Astronomy in college. I can tell ya all about a Parallax flux measurement or the relative heat of a star from it's color and that's about it.

Farmer Liz said...

Oh I love seeing chemistry applied in practice! As a chemical engineer I feel I should step in here and make sure we have the basics right. Although maybe I should wait for part 3 to see what happens next, this is a nail-biter!

Baking soda, sodium bicarbonate reacts with acid to produce salt + water + CO2. A base (such as potassium hydroxide) with acid will produce a salt + water. No heat activation required to produce CO2. I not sure about that paragraph you quoted, as the reaction is not "with" CO2, but it PRODUCES CO2, if that makes sense.

I am wondering if you only see the bubbles when the carbonate is in solid form, as you had bubbles with baking soda and with the ash, but not the liquid. You definitely extracted something from the ash, as you had a high pH, but do you need to soak more ash to get enough carbonate?

My other interest in wood ash is using the liquid to make lye for soap. I found an old book that described dripping rainwater through wood ash. That is a project for winter when I have some ash to play with.

I am really looking forward to part 3 and having a play around with this myself some time soon :)

Farmer Liz said...

Oh one more suggestion, you can try mixing the acid and ash water in a small jar (ideally a test tube!) and quickly put a small balloon over, it inflates you have produced a gas, hopefully CO2!

Michelle said...

I enjoy seeing that you are trying to use what you have and test it out in the kitchen. I would like to use the wood ash in soap making.

Leigh said...

I had forgotten all about salt risin bread. Thanks for mentioning that! It will be something else to experiment with and include in my "Baking Without Baking Soda" eBook.

Leigh said...

Yes, if the soil is alkaline it will fizz. It's all a pH reaction, although I don't completely understand it all. The real test will be in the baking.

Leigh said...

I love hypothesizing and love to hear others' ideas too. :)

I know that baking soda reacts to heat, but it works better with thin things like cookies and crackers. For cakes and muffins an acid is needed as well.

I know that in double-acting baking powder, the sodium aluminum sulfate reacts with heat, and is why double acting powder allows for a little leeway as to when it goes into the oven.

So far tidbits like that are just scattered bits of information in my brain. Haven't got it all figured out yet. I'm hoping the baking experiments will help!

Leigh said...

You mean soaking it in the water? Anything goes! Experimenting is half the fun.

Of astronomy, I'm only good for finding Orion, the Big Dipper, and the North Star. :)

CMRS said...

I first read about hartshorn from King Arthur Flour https://www.kingarthurflour.com/tips/quick-bread-primer.html. Also, here is a cool link about salt risin bread.
http://www.popsci.com/article/science/clostridium-it-can-kill-you-or-it-can-make-you-bread

Leigh said...

Thanks for that Liz. I have a few more puzzle pieces for part 3, even though I still can't put the puzzle together. :) I would think that any base should react with the vinegar to get at least some CO2. (But again, I'm no chemistry whiz).

Homemade lye for soap is also on my list of to-learns. I'll look forward to your experiments too!

Leigh said...

Good idea. I wonder that if the carbonate can react with water, that I may have lost the CO2 early on.

Leigh said...

That's another excellent use of wood ash. And also on my list!

Leigh said...

Hartshorn, yes! That's another one. From what I've read, it reacts to heat and so doesn't need an acid added to the recipe. (Now I'm wondering if goats horn would work too.)

Thanks for the link about the salt risin bread, too. I'm going to have to dig out my recipes for it and add it to "How To Bake Without Baking Powder."

Lady Locust said...

Part 3? You're killin' me here, Leigh:) I agree with Renee's comment~ that's the good ol' way of making lye soap. Lye in water raises the temp. and essentially 'cooks' it as it reacts. Heat might be a fun thing to try. Do you have a fire extinguisher - just in case? I love chem.

Jake said...

I should clarify...what I was saying in the paragraph above was in reference to the part in the first post that said CO2 reacts with the pearl ash to make potassium bicarbonate.

The ash water likely contains mainly potassium hydroxide (KOH) and potassium carbonate (K2CO3). In making the pearl ash, the potassium hydroxide reacts with CO2 to make potassium bicarbonate:

KOH + CO2 = KHCO3

The actual reaction sequence is probably more complicated, but that's the overall result. During baking, the KHCO3 reacts with an acid to make CO2, as Farmer Liz says, but can also give off CO2 by heating.

I'd wager that what you extracted was a lot of KOH and not a lot of K2CO3, although I like Farmer Liz's idea of trying to capture any gas produced in a balloon. But if my guess is correct, you could try to convert the KOH into KHCO3. In the olden days, they did that by drying down the ash water to give a solid, then passing CO2-containing combustion gases over the solid. You could maybe get a similar effect by blowing bubbles through your ash water with a straw for a couple hours. :-) (respiration produces CO2)

On the other hand, there must be some of the carbonate in the ashes because it bubbled when you added vinegar. You might be able to get more of it out by making your ash water with hot water.

I'm on the edge of my seat to see what happens in part 3; this series has really got the ol' gears turning! Thanks for doing these posts!

And also, thanks for the blog shout-out! :-)

Leigh said...

Deborah, thank you for that! I've been trying to think how to do this - how to burn a corn cob and collect the pure ash.

I haven't shelled this year's corn harvest yet, but I usually get a few red cobs every year. Once that happens, I plan to experiment.

Leigh said...

Sorry! LOL. I planned to go right on to the baking experiments, but these non-reaction results surprised me and triggered more research.

Yes, that you're right about the thermal reaction of lye in soap making. Of course, modern soap makers usually use sodium hydroxide (caustic soda) to make hard soaps, and potassium hydroxide (caustic potash or potash lye) is used for soft soaps. It's the potassium hydroxide that comes into play with hardwood ash. (Sounds like another chemistry lesson in the making!)

Leigh said...

Jake, you're very welcome for the shout out. There's a lot of good stuff on your blog. :)

Thank you for the more detailed explanation. It definitely helps and I'm getting a better idea of why potash rather than wood ash was used (more than just aesthetics) and later pearlash. Liz emailed and gave me the same suggestion about the hot water, so I'll try that next.

It was all so innocent in the beginning and I'm amazed at how complicated it really is. I think I need to get on to the baking experiments, because that was the point in the first place, although I'm learning a lot of valuable stuff in the process!

Leigh said...

I should mention that there is a soap-like reaction that occurs in baking with these old alkalis, and accounts for a bitter or soapy taste that occurs sometimes. That's apparently why folks preferred the improvement of saleratus and baking soda!

charlotte said...

Very exciting! I am looking forward to the sequel!

Leigh said...

Coming soon...

The Stay @ Home-Gardener said...

YAY! SCIENCE! I find it far more interesting now than back in Chem class. :)

Shane said...

If your simply looking for an alternative to baking soda ( calcium bicarbonate) you could try finely ground up egg shells (calcium carbonate). might have to bake the egg shells first to kill bacteria and remove moisture. just a thought

Leigh said...

Cloud! Good to hear from you. I have to agree how much more interesting things are not that they aren't required courses (or even electives, for that matter). I have to say the same about math and history. And not only are they more interesting, but I seem to be able to grasp the subject matter now that I'm older and not under pressure for a grade. :)

Leigh said...

Shane, that's an interesting idea. In exploring food grade alkalis, egg shells is not one I thought of. That is probably because I did some experimenting years ago, with egg shell as a calcium source. I dried and ground them, but could never get them fine enough to not have an unpleasant grittiness to whatever I put them in. Perhaps with a fine enough grind ....