Did you know that baking soda (sodium bicarbonate) is amphoteric (react with both acid and bases)? I didn't until recently. I know by combining baking soda with some kind of acid will set off fizz, that's how we make bath bomb (or fizzy) to self disperse in bath tub filled with water. A quick kitchen sink drain cleaning is to flush down some baking soda with vinegar. But, I've never tried reacting baking soda with a base. I just learned recently that reacting with a strong base baking soda would turn into washing soda which is a water softener.
Since baking soda reacts with lye which is a strong base, making cold process soap with baking soda is somewhat tricky. I have seen soap makers failed by adding too much baking soda into the soap batter. Too much baking soda added would end up off setting the normal saponification process and resulting in mushy soap, which is not soap at all.
As curious as I am, I just have to try this. I live in a hard water county, majority of our water source is from the underground. We did install a heavy duty water softener tank in our garage where the water enters the house, but it's never as good. In fact I cannot bring myself to drink the tab water, it tastes funny, yucky. I can never have a luxurious bubble bath with 10 inch high foam because my water is hard. If adding baking soda in soap can help combat the hard water and cut down soap scum I think I would feel like I hit the jackpot.
To prevent baking soda off setting normal saponification I decided to use lower lye discount and only add 5% of the oil weight. Since all I heard from other soap makers' horrified story is that baking soda reverses trace, I decide to take a water discount. With 5% lye discount, 5% baking soda, 33% lye concentration, my first baking soda soap didn't go too well. It went way pass plan A, totally skipped plan B straight to plan C which is just trying my best to squish all I can into the mold before it started to harden.
I was not surprised at all when I unfolded this small 5 bar test log, there were potholes EVERYWHERE.
It was very bad. This photo was taken after I tried to patch up some potholes using the scrap soap from the soap pots. There wasn't enough scrap to fill all that holes. I had to sacrifice 1/2 bar of soap to fill the rest of the holes. These are the 4 bars left:
How did I fill those potholes?! Soap is still considered soft and pliable when first unmolded. All I have to do it smash it like clay and push it into the holes with a knife (or scrapper). This only works the first couple hours of the soap out of the mold, else it gets too dry to work for seamless patching.
2 days later I took a sample piece to the sink for lather testing. I can still feel the baking soda, it smells powdery and a little chalky, but not scratchy. So far I'm not seeing a noticeable different in lather, maybe I'll wait a few weeks to wash again.
Interesting! You managed to fill those potholes well, lower photos are great!
ReplyDeleteLovely colours! But what is the advantage of a baking soda soap?
ReplyDeleteAs I wrote in the post it is to form washing soda, a water softener agent, soften your skin and help lather better and cut the soap scum residue.
DeleteI'm a soaper and a massage therapist. I've been trying to make a soap with the addition of baking soda for a very good reason.
DeleteStinky clients. The truth is that about 5% of the people who get worked on, have some kind of oil based odor of which they're unaware. Once in a while, someone is particularly smelly and I have to scrub to my elbows with soap and baking soda in an attempt to get that smell off of me. And that stink sticks, let me tell you. I want a baking soda soap for odor control.
I've mad e a couple of failed attempts (turned out mushy or just...failed) but I'm not giving up. I thought I might coat a course salt in baking soda and try that next.
what about a coffee soap for the odour?
DeleteAdding some salt will do the same thing more easily, with no fear of intercting with lye. Sort of like salt-based water softeners. :)
ReplyDeleteJenny
Baking soda is a fun additive. We like to experiment in our lab too. It provides great exfoliation on the skin when used in rebatch soap.
ReplyDeleteIf I add baking soda to rebatch or M&P soap, will it maintain it's exfoliating properties?
DeleteI'm not sure the best way to get washing soda in your soap is with baking soda. Since it reacts with and consumes lye, it can lead to really screwy saponification in cold process, since you have two competing reactions going at the same time. It's best to just use baking soda in rebatch. If you want washing soda, it might work out better to just add washing soda to your soap. You can find washing soda in places that sell dye for fabric-dying. However, I don't know if it's a good idea to use it on your skin, it's harsh stuff. Usually it's only used for washing things and clothes, not people.
ReplyDeleteAfter testing the soap in my sink I determined baking soda dries out my skin, I don't see the perk of using it at this point. I have the same question you mentioned too about what happens when adding washing soda to lye. I think I'm just going to let this whole idea of baking soda soap go. Thanks for your great info!
DeleteI'm just happy I could offer something that helps you! You always have so much fascinating info on your blog. You make the most amazing soaps. I try, but my stuff never comes out that great. My soap works ok, but the appearence leaves a lot to be desired. I understand chemistry, but I'm not much of an artist. My swirls come out smeary and anything I try with a frosting tip always looks like a giant, shapeless blob. I love looking at all your beautiful photos.
DeleteI'm glad to have someone who's good at chemistry offering her priceless information! Everyone is is good at something and that's why we are unique as an individual. Or should I say grass is always greener on the other side of the fence?! LOL I often envy the ones who got scientific brain!
DeleteBaking soda is a great, gentle and natural exfoliant for me. In the shower i use an old spice contaner filled with baking soda (it has a shaker top that is easy to use and keep the soda dry). Shake a little in your hand and rub on your face with a little water. Another option is to add a few shakes to your daily facial cleanser. My face comes out smooth and squeaky clean! Hope you try, it works great.
ReplyDelete