Why Distilled Water for Lotion?

[MellonFriend]

I'm a bit confused as to why it is that you are supposed to only use distilled water for lotion making. Recipes claim it is because distilled water is free of microbes, couldn't I just boil some water instead to kill any little guys living in the water before I use it? Essentially pasteurize the water? Another reason is metals in the water. What's the big deal about metals being in water? Does it contribute to rancidity?

 

[DeeAnna]

Yes, metals can contribute to rancidity in lotion as well as in soap.

 

[MellonFriend]

Yes, metals can contribute to rancidity in lotion as well as in soap.

Do you happen to know the science behind this?

 

[TheGecko]

Simple science...you will need 6 plastic water bottles. Fill two bottles straight out of your sink, two with filtered water and two with distilled water; put a tea bag in each bottle. Stick all six bottles on your window sill; open one of each of the bottles and then leave them for a good month***. Look at what is the inside of your bottles after water evaporation. Look at what is in the closed bottles, pour some over your hands and feel the liquid, smell the liquid and though I don't recommend it...take a small sip. Repeat the experiment with boiled water, but the results will be similar.

I'm not a science person, but I know the practical effect of air, heat and light on water. If I make a pitcher of tea from the tap and put it on the counter...it's good for about two days before it starts to 'turn'; three days with filtered, four days with distilled. Even pre-bottled tea from the store that is manufactured under strict guidelines and can sit in my garage for a month or more unopened and be perfectly good...will go bad once the seal has been broken.

**** - This test would actually be better in the Spring or Summer

 

[MellonFriend]

Simple science...you will need 6 plastic water bottles. Fill two bottles straight out of your sink, two with filtered water and two with distilled water; put a tea bag in each bottle. Stick all six bottles on your window sill; open one of each of the bottles and then leave them for a good month***. Look at what is the inside of your bottles after water evaporation. Look at what is in the closed bottles, pour some over your hands and feel the liquid, smell the liquid and though I don't recommend it...take a small sip. Repeat the experiment with boiled water, but the results will be similar.

I'm not a science person, but I know the practical effect of air, heat and light on water. If I make a pitcher of tea from the tap and put it on the counter...it's good for about two days before it starts to 'turn'; three days with filtered, four days with distilled. Even pre-bottled tea from the store that is manufactured under strict guidelines and can sit in my garage for a month or more unopened and be perfectly good...will go bad once the seal has been broken.

**** - This test would actually be better in the Spring or Summer

I don't doubt that it's the case, that there are impurities in the water, I want to know why it is that metals in the water contribute to spoilage. What exactly molecularly is happening?

Edit: I think I misunderstood you. You were trying to exhibit the effects of boiling/not boiling water plus distilled/not distilled on microbe content?

 

[cmzaha]

My opinion of using distilled is to possibly ease some of the load for my preservative system. Not being a chemist with a full-blown test lab I am going to take every precaution I can when making lotions. I simply cannot be sure metals and whatever else is left in the water might have an effect on my preservative so I would rather use distilled water and do for lotions. I just want to cut off all the avenues I can for problems, such as using aloe juice and hydrosols, which I use in very low percentages in a couple of lotions.

 

[MellonFriend]

I set my science-oriented sister on a mission to help me explain to me the effect of metal on rancidity, and I think I understand it now. Basically, it's as simple as the metals acting as a catalyst to speed up the rancidification process. I agree with you, cmzaha after hearing from her a rundown of all the things that contribute to spoilage in oils. Water, microbes, and metals. Sure would be nice to eliminate as much of the problem as possible by using distilled instead.

Thanks for helping me work this out, all of you!

 

[justjacqui]

There are large variations in the quality of drinking water with some areas having very hard tap water (high levels of calcium and magnesium).

Apart from putting additional strain on your preservative system the salts (metal ions) in drinking water can also interfere with other ingredients in your product. Many ingredients are sensitive to salt (e.g. some polymeric thickeners) and will not work properly in the presence of tap water. Iron can also cause color changes with some ingredients.

Using distilled water also ensures that if you move to a different location you shouldn't have problems because of water quality.

 

[DeeAnna]

I don't doubt that it's the case, that there are impurities in the water, I want to know why it is that metals in the water contribute to spoilage....

It's well known chemistry that some metals accelerate the rate at which fats oxidize and become rancid. This information is readily available in the fields of food chemistry field as well as cosmetic chemistry.

If you want the longest life from your fats, you want to reduce the level of trace metals that your fats are exposed to. This means using water that has been treated to reduce metals to a minimum -- distillation, demineralization, and reverse osmosis are all treatments that reduce metal contamination in water.

In addition to minimizing metals in your raw ingredients, it's also smart to use a chelator in your soap, lotion, etc. A chelator is a chemical that is able to bind with and immobilize trace metals.

 

[MellonFriend]

It's well known chemistry that some metals accelerate the rate at which fats oxidize and become rancid. This information is readily available in the fields of food chemistry field as well as cosmetic chemistry.

If you want the longest life from your fats, you want to reduce the level of trace metals that your fats are exposed to. This means using water that has been treated to reduce metals to a minimum -- distillation, demineralization, and reverse osmosis are all treatments that reduce metal contamination in water.

In addition to minimizing metals in your raw ingredients, it's also smart to use a chelator in your soap, lotion, etc. A chelator is a chemical that is able to bind with and immobilize trace metals.

Okay cool. I did not know that that's what a chelator is. Everything makes so much more sense now.

 

[MellonFriend]

Would it then be a good idea to add citric acid to my lotion recipe for chelating powers like I do in my soap? I'm seeing online that it can be done. Is there a usage rate anyone can recommend and when to add it to the recipe?

 

[AliOop]

I've only seen it used as a pH adjuster in lotions. I don't think you'd want to add it without being sure that it won't take your pH too low, or mess with your emulsifier or your preservative.

Since pH and preservatives are so important in lotions, they are definitely trickier and more "science-y" than soaps. Also, there is such a variety of ingredients, some of which don't play well together at all.

 

[DeeAnna]

No, citric acid doesn't chelate. Sodium citrate is a chelator, which is the salt formed when sodium hydroxide and citric acid neutralize each other.

Soap makers may add citric acid to their batches, but their soap has sodium citrate in it, not citric acid. Unfortunately the common belief that's arisen from this practice is the citric acid is a chelator in soap, when it's technically not.

The problem with adding a salt like sodium citrate to an emulsified lotion is that salts can affect the emulsion. Not to say you can't add salts to lotion, but if you do add a salt without understanding all of the effects the salt can create, you might get unexpected results. I think using chelators such as disodium EDTA or sodium gluconate is a better idea -- they're widely used in products like lotions.

Adding several salts (or too much of any one salt) to soap also create problems. One example I can think of was when someone was adding citric acid and table salt to their soap, and reported their soap was rubbery and soft.

 

[MellonFriend]

Well I'm sure glad I asked you guys, before giving it a try! Sounds like this is just a potentially unnecessary complication at this stage of my lotion making process. I'll just stick to the recipe I have and not try and tweak it until I see it's necessary.

 

[AliOop]

Thank you @DeeAnna for the science behind the concerns about using CA in lotions. That makes it so much more understandable than just saying “don’t” or “be careful.”

I do like making lotions, but they definitely have so much less margin for error than soap or even anhydrous body care products. It was daunting for me at first, so I really appreciated the knowledge on this forum to help me feel confident to start, but not overconfident to throw in the kitchen sink.

 

[TheGecko]

All this is why I don't make certain stuff from scratch.

 

[MellonFriend]

Thank you @DeeAnna for the science behind the concerns about using CA in lotions. That makes it so much more understandable than just saying “don’t” or “be careful.”

I do like making lotions, but they definitely have so much less margin for error than soap or even anhydrous body care products. It was daunting for me at first, so I really appreciated the knowledge on this forum to help me feel confident to start, but not overconfident to throw in the kitchen sink.

I totally agree. I love knowing why something is the case and not just that it is. I'm so glad to have this kind of community to turn to!

 

[cmzaha]

I use disodium EDTA in my lotions.

 

[Misschief]

I use disodium EDTA in my lotions.

At what percentage, Carolyn?

 

[DeeAnna]

At what percentage, Carolyn?

Not Carolyn, but I want to contribute anyway. My notes suggest about 0.02% by weight EDTA powder based on the total batch weight of lotion. Yes, that's a teeny tiny amount.

Disclaimer: I have just recently started to include a chelator in my lotions, so my real-world experience is limited. Hopefully Carolyn will share what she recommends -- she has a lot more experience to back up her recommendations. @IrishLass is another person who uses a chelator in lotion -- perhaps IL will also share what works for her.

You will want to use DIsodium EDTA for products like lotions that have a neutral to acidic pH (pH at or below 7). TETRAsodium EDTA should be used in soap, because soap is alkaline (pH above 7).

In addition to extending the shelf life of fats in a lotion, the use of a chelator also boots the effectiveness of the preservatives added to lotion to inhibit microbial growth. Certain trace metals are required to support living organisms. If the chelator immobilizes those metals, then microorganisms in the lotion will find it harder to reproduce and thrive.

Just to be clear -- A chelator is NOT a preservative. Use it IN ADDITION TO a broad spectrum preservative, not in place of a preservative.