Tuesday, October 20, 2009

Citric acid

Citric acid (or 2-hydroxy-1, 2, 3-propanetricarboxylic acid) is a chelating, anti-oxidizing, and pH altering ingredient that can bind metal ions, help prevent rancidity, and alter the pH of our lotions and surfactant mixtures. It's also a key ingredient in bath bombs.

There are two types of citric acid we can buy - anhydrous (water free) and monohydrate (contains water). I have found the anhydrous citric acid I've bought tends to be a powder and, for me, makes bath bomb creation a far easier process than using the monohydrate, which I've noticed tends to be more like a grain. The anhydrous is much less likely to fizz in high humidity, which means you can use it in bath bombs even when its damp outside! (I used to get mine at Voyageur, but they've stopped carrying the powder form, so I get it at Aquarius. Ask your supplier which one you have!) For other applications, it's irrelevant which one you choose.

It is a chelator like EDTA, which we can use to bind metal ions like calcium, magnesium, copper, zinc, nickel, and cobalt to keep our products from experiencing auto-oxidation. By binding these metals, it also keeps surfactant mixes nice and clear! It also helps to boost the efficacy of your preservative.

The difference in using citric acid as your chelating or sequestering agent is the pH changes you might find with it. Citric acid is a weak organic acid, which means it has a pH less than 7 (it ranges between 3.13 to 6.4 depending upon the concentration). When we add it to a lotion or surfactant mix, it can change the pH of our product. For something like a hair care product, we want a pH around the pH of our hair, which is 5.6 to 6.2. For a lotion, we want a pH around 5 to 6 - our skin is about 5.5.

Including too much citric acid in something like a shampoo can change your hair colour! Remember "Sun In"? (It was all the rage when I was a teenager - eek, I'm dating myself here!) It can lighten your hair if you're using too much of it! (You do have to use a decent amount - say 1% or more, so the 0.1% suggested below should be fine!)

Citric acid can be used as an AHA type acid in facial products, but as I've not used it in that context before, I'm not comfortable making any suggestions for use. It can also be used as a buffer (something that maintains the pH of a product) with sodium citrate if you're using things like AHA or Multifruit or Phytofruit or another acidic ingredient.

How much to add? You only want a titch when you're using it as a chelator and anti-oxidant - 0.1% or so - and this shouldn't be enough to change the pH dramatically. If you're using citric acid at higher levels, I'd suggest getting a pH meter (it's on my Christmas list) or using those pH strips.

If you are interested in learning more about acid-base reactions and pH, you can start here with the Wikipedia entry. If you're interested in learning more about buffers, again I offer you a Wikipedia entry!

Join me tomorrow for a discussion on how to determine the shelf life of your lotion, then a closer look at linoleic acid!


Anonymous said...

Can citric acid be used to neutralize Hydrovance?

Susan Barclay-Nichols said...

Do you mean directly into the bottle of Hydrovance or into products in which you've used Hydrovance?

Anonymous said...

In a recipe I guess I have not used hydrovance yet and am wondering about the ph. Does hydrovance make a cream go more acid or more alcaline overtime?

Thanks Susan!

Susan Barclay-Nichols said...

I've written a post about Hydrovance here. It will make the product go more alkaline (increase in pH), and a lot of our preservatives are ideally used at neutral or slightly acidic pH levels (6 or lower), which means our preservatives may be de-activated!

Yes, you can use citric acid to bring the pH down in a product with Hydrovance, but Hydrovance likes to be at a neutral pH, so there's a dilemma there. If you bring the pH down originally, it will increase the pH drift. If you leave it at a neutral pH, the pH drift will slow. You're better off using a buffer of some sort. Here's a great PDF on this topic from National Starch!

Anonymous said...

Hi again Susan!

Thank you so much for clarifying the Hydrovance's process of drifting, couldn't be clearer. The reason why I was asking about using citric acid to change the ph, was cause I had read the pdf on it but cannot find a place to purshase those buffers.. would you have a suggestion please?

Thank you Sue!

Anonymous said...

PS Would you know approximately how long it takes for Hydrovance to have a significant change in Ph?
I could also make smaller recipes that could fit that time period...


Blogger Here said...

Is Citric acid required when making shampoos, conditioners and intense deep conditioners?

Susan Barclay-Nichols said...

Do you mean to alter pH? It depends upon the recipe. None of my recipes need to be altered.

Anonymous said...

What concentration of citric acid should be used to change the pH of formulation?

Anonymous said...

Hi Susan, I've made quite a few body and face products from your site. Thank you so much for the effort you do here. We now have a favorite family body salve each with our own version of scent. {smile} Anyway, I'm commenting on the Citric Acid {I have some}because I'm venturing into homemade cleaning products. The recipes usually contain liquid Castile soap, essential oils, washing soda, baking soda, tap water {I'd only use distilled} and vinegar. I want to subsitute citric acid for the vinegar and wonder on the rate of substitution. I think people just think the citric acid is hard to find... Seems like a way better choice to avoid the stink of white vinegar. Anyway, here's a sample of the average recipe. I was also going to add some liquid germal. Do I even need a preservative with the citric acid? This is to clean the floors and counters. I'd love to see you do a series on some homemade cleaners for around the house. If you've done some posts for that, please point me to them, I'd love to read them. {I'll check back here} Thank you ahead, Dawn

Anonymous said...

Sorry, it'd help if I attached the sample I mentioned. {smile}

1 tsp Borax
2 Tbsp Vinegar
1/2 tsp Washing Soda
1/2 tsp Castile Soap
20 drops Tea Tree Oil
2 Cups Hot Water

They're all along these lines.

Thanks Again, Dawn

Anonymous said...

I know too... this recipe is all in tablespoons and such. I wish it were percentages. It's all I could find. I'm trying to replicate Sol U Mel from Meleluca actually. They use Tincture of Green Soap, SD Alcohol 40 and Tea Tree Oil. Was going to order the Green Soap online and skip the alcohol. Anyway it led me to finding all the other recipes like the sample I gave you. I've blabbed enough. Thanks Again, Dawn

Anonymous said...

Here's another version... You can see why I wonder about the rate to substitute the vinegar.

3 Cups Water

¼ Cup Isopropyl Alcohol

¼ Cup Dishwashing Liquid (like Dawn, Joy, Method, etc.)

2 Tbsp. Citric Acid

Essential Oils (optional)

Last comment, I promise. Dawn

Susan Barclay-Nichols said...

Sorry, Dawn, I really can't make any suggestions as I use vinegar for my products and I haven't experimented with citric acid. The question becomes - why are we including vinegar at all? I think the answer is that we like the cleaning power of it for our products. How does it clean?

You know, I think this would make a good post...Look for that shortly!

Tonje Richards said...

I bought some hyaluronic acid powder and made a gel of 100ml. How much citric acid would i need to use to preserve it?

Susan Barclay-Nichols said...

Hi Tonje! Citric acid isn't a preservative. As I mention in the post, it's a chelatinh agent and pH adjuster. Use this in a gel, and it'll destroy the viscosity.

Anonymous said...

Thanks for the reply, Susan. I did end up tinkering with the cleaners. I had a residue left behind though and researched some more. I learned Castile Soap is not to be mixed with anything acidic, that they neutralize each other and do not clean as well together. So, I adjusted the recipes and used either vinigar or Washing Soda... or Castile Soap with the other ingredients. Things were cleaner afterwards with no streaking or residue left behind. Which I found out... the residue was actually 'soap scum' that formed in the streaks! I'll keep an eye out for that post. Thank you so much. Dawn

fajri66 said...

0,24% Citric acid has pH around 2,60 - 2,70..U can add 0,9% Trisodium Citrate to make it buffer pH around 3,44..mostly those combination use in the ready to drink beverage which pH around 3,2-3,5..Citric acid can provide sourness and trisodium citrate can adjust pH u are required..it won't be a dillema..

Susan Barclay-Nichols said...

Sorry, what? This doesn't make any sense to me, and I'm not sure what it all means. Can you please be more clear?

T Nemwan said...

Hi If I'm using Neodefend as a preservative in a lotion and I also adjusted the PH with citric acid, will the Neodefend have the same issues (creating benzene) as it has it vitamin C? Thanks so much for your help! Tiffany