by Catherine Haug
At our September Gathering on Natural Dyes, these common household substances were discussed. As an adjunct to that discussion, I’d like to expand a bit on each.
Baking Soda
Also known as sodium bicarbonate, baking soda is one of two salts of carbonic acid (dissolved CO2). It’s chemical formula is NaHCO3 and dissolves into water in its ionic form: Na+ and HCO3-. It is considered a buffer, meaning that it can bring the pH of an acidic or an alkaline solution toward neutral.
[pH is a measure of the acidity/alkalinity of a solution, in a range of 1 – 14. pH 7 is considered neutral; below 7 is acidic, and above 7 is alkaline]. The pH of baking soda is 8.1, slightly alkaline.
It is the HCO3- part of baking soda that does all the work by picking up another H+ ion (from an acid) to produce CO2 gas and H2O (water).
Uses for baking soda
Soda’s ability to convert to CO2 when in the presence of an acid is how it works as a leavening (rise agent) in baking. On its own, it won’t cause a rise, but in the presence of an acid such as vinegar, lemon juice, yogurt, it reacts to release CO2 gas. This gas creates bubbles in the mixture, effectively causing it to rise. (Other batter acids include buttermilk, sour cream, chocolate, cocoa, honey, molasses, brown sugar, fruits and maple syrup). (4)
And it can be used to reduce the acidity (increase the pH) of a dye solution, as demonstrated by Joan G. at our September gathering.
Other uses: removing certain stains (see Baking soda and stain removal (1)), for absorbing odors, and for brushing teeth.
Baking Powder
Some enterprising baker figured out that you could combine baking soda with a salt of tartaric acid (cream of tarter) that would remain an inert powder until added to a batter. Upon contact with the liquids in the batter, the cream of tartar forms tartaric acid, which in turn reacts with the baking soda to release CO2 gas.
Thus your batter doesn’t need to contain an acid (buttermilk, yogurt, lemon juice, etc) in order to rise, because the leavening agent (baking powder) contains the acid.
However, I must point out that most commercial baking powders contain aluminum salts to absorb moisture that would otherwise destroy the leavening power of the mix, and aluminum can be toxic. So it’s best to buy aluminum-free baking powder, or make your own, using arrowroot or cornstarch to absorb moisture. I prefer to use arrowroot because commercial cornstarch is made from GMO corn.
Sift together the following, and store in an airtight glass jar:
- 2 parts cream of tartar
- 1 part baking soda
- 2 parts arrowroot powder (or 1 part cornstarch)
Or to make it up as needed (3):
For each teaspoon baking powder called for in the recipe, use 1/4 tsp baking soda and 1/2 tsp cream tartar.
Recipes with both baking soda and baking powder
One might ask, why do some recipes call for both baking soda and baking powder? This is common when a recipe contains a little bit of acid, but not enough to activate the baking soda on its own. For example, bananas in banana bread. In this case, the baking powder does most of the leavening, and the soda neutralizes the acids that would give a sour taste, and to increase the tenderness (crumb) of the final product.
Similarly, when yeast is used as the main leavening agent, baking soda can be added to neutralize acids in the dough. For example, buttermilk dinner rolls; baking soda neutralizes the sourness (acidity) of the buttermilk.
The trick is coming up with the right proportion of baking soda and baking powder, when developing your own recipes. I presoak my flour in a yogurt-water solution overnight, before mixing up the batter. This is to make the minerals in the flour more absorbable, and to partially break down the gluten and other proteins for easier digestion. But because yogurt is sour, I then add a bit of baking soda to the batter after the presoak, to neutralize that sourness.
Note that baking soda is about 4-times as strong as baking powder, but once you have allowed the baking soda and acidic batter to mix, you can not delay putting the batter in the oven, or it will fall. On the other hand, baking powder is double-acting, meaning that the first action producing gas bubbles happens when the batter is mixed, and the second action happens when it is heated. Thus you can have a short 15 – 20 minute delay after mixing the batter before you put it in the oven. (4).
Washing Soda
Washing soda (also known as sodium carbonate, sal soda, or soda ash) is another salt of carbonic acid (from CO2); its molecular formula is Na2CO3. It is more alkaline than baking soda, but not as alkaline as lye. It is formed when an alkali (such as lye) is added to a bicarbonate solution (baking soda). The OH- of the alkali reacts with the NaHCO3 to form H2O and Na2CO3.
Washing soda should not be used as a substitute for baking soda in recipes, as it is highly reactive.
While baking soda is almost neutral (pH 8.1), washing soda is quite alkaline (pH 11); remember that pH 7 is neutral. And it is this alkalinity that makes it very useful in the laundry for removing tough grease stains from tough fabrics; however, it should not be used with soft fabrics as its caustic nature may harm them. Washing soda is also useful for removing petrol from garage floors, or grease buildup in your oven. (5)
Cream of Tartar
Also known as sodium bitartrate, cream of tartar is one of the salts of tartaric acid. Grapes are the only significant food-source of tartaric acid; commercial sources of tartaric acid are from the waste products of wine-making.
Its molecular formula is (COOH)CH(OH)CH(OH)(COOH); it is the COOH that is the acidic part, by releasing the H+.
Uses for cream of tartar
It is used in combination with baking soda to make baking powder, a leavening agent for non-acidic batters (see above).
It can also be added to the water in a canning bath or pressure canner, to prevent mineral stains on your jars.
When mordanting fibers with alum before dying, it acts to increase the acidity of the solution. (See Gathering Summary: Using Natural Dyes for Fibers (7)).
See eHow for more uses (6).
Sources:
- housekeeping.about.com/od/stainremoval/qt/bksd_staintreat.htm
- www.armhammer.com/basics/magic/
- www.dianaskitchen.com/page/recipes03/0905_bakingpowder.htm
- www.joyofbaking.com/bakingsoda.html
- www.buzzle.com/articles/washing-soda-vs-baking-soda.html
- www.ehow.com/how_2081866_find-more-uses-cream-tartar.html
- Gathering Summary: Using Natural Dyes for Fibers, essentialstuff.org/?p=4117