Why don’t bath bombs need preservatives?

[Shaylyn Valdez]

I see a lot of people use rubbing alcohol and water as a binder, but I thought if you add water to a product you need a preservative? Is it because it evaporates?

 

[earlene]

The reason that preservatives are needed in cosmetics to which water may be added (either in the formula or in expected use) is because water is a medium for microbial growth.

In making bath bombs, I have not used water, but witch hazel or alcohol. Here is a link about when to use preservatives: Preservatives Quick Guide - Soap Queen

You will notice the following statement: "Bath bombs don’t contain water so they don’t need a preservative. When choosing witch hazel to wet them, make sure it’s alcohol based or already has a preservative." She indicates that making bath bombs with water was or is either not as common as you may think, or that it is not suggested. I have read warnings NOT to use water to make them because it will activate the Citric Acid and start the fizzing process, although I have seen recipes that do suggest the use of water. But IMO using water to make bathbombs, at least in my climate, would be asking for trouble.

I have seen what high humidity does to bath bombs left to dry in high humidity. They don't; what they do is fizz up and grow like a slow-moving volcano.

 

[lsg]

I don't use water in my bath bombs, either. Water creates a friendly environment for bacteria and molds. That is why preservatives are used when water is present in the ingredient list.

 

[AliOop]

I use 91% RA so I believe that the small amount of water in that does evaporate by the time I'm done mixing. I've never used a preservative in mine.

I also add the CA last, after all other dry and liquid ingredients have been mixed, including the fragrance, poly80, etc. That has eliminated all fizzing or activation for me, but then, I live in a pretty dry climate. For those in a more humid location, I highly recommend @lsg 's no-water recipe that she has posted in other bath bomb threads.

 

[Shaylyn Valdez]

The reason that preservatives are needed in cosmetics to which water may be added (either in the formula or in expected use) is because water is a medium for microbial growth.

In making bath bombs, I have not used water, but witch hazel or alcohol. Here is a link about when to use preservatives: Preservatives Quick Guide - Soap Queen

You will notice the following statement: "Bath bombs don’t contain water so they don’t need a preservative. When choosing witch hazel to wet them, make sure it’s alcohol based or already has a preservative." She indicates that making bath bombs with water was or is either not as common as you may think, or that it is not suggested. I have read warnings NOT to use water to make them because it will activate the Citric Acid and start the fizzing process, although I have seen recipes that do suggest the use of water. But IMO using water to make bathbombs, at least in my climate, would be asking for trouble.

I have seen what high humidity does to bath bombs left to dry in high humidity. They don't; what they do is fizz up and grow like a slow-moving volcano.

I don’t believe there is a way to get 100% isopropyl alcohol so that’s false in saying you don’t use water if you use 91% rubbing alcohol like a lot of people use because the other 9% is water.

 

[AliOop]

@Shaylyn Valdez It was I, not Earlene, who uses 91% RA. And I didn't say that it didn't include water - I said that I believe that this small amount of water evaporates.

 

[earlene]

I don’t believe there is a way to get 100% isopropyl alcohol so that’s false in saying you don’t use water if you use 91% rubbing alcohol like a lot of people use because the other 9% is water.

No, I don't think there is a way to get 100% alcohol either, and even witch hazel has some water in it as well, but what I was saying was that I don't use 100% water, as in distilled water as the liquid.

Of course I know the percentage make-up of the different rubbing alcohols, but thank you for pointing that out. I am sure that is not the only thing I left out in my comment.

 

[Shaylyn Valdez]

No, I don't think there is a way to get 100% alcohol either, and even witch hazel has some water in it as well, but what I was saying was that I don't use 100% water, as in distilled water as the liquid.

Of course I know the percentage make-up of the different rubbing alcohols, but thank you for pointing that out. I am sure that is not the only thing I left out in my comment.

I’m sorry if my reply came off rude! I was rereading it now and was like oh my goodness I sound so rude here haha. Don’t reply when you’re tired

 

[Shaylyn Valdez]

@Shaylyn Valdez It was I, not Earlene, who uses 91% RA. And I didn't say that it didn't include water - I said that I believe that this small amount of water evaporates.

My bad! I replied while tired which is what I get! I didn’t mean to come off as rude either so my apologies if it did!! Thank you for all of your helpful inputs!

 

[AliOop]

No worries @Shaylyn Valdez and best of luck for a successful batch.

 

[user 49910]

No, I don't think there is a way to get 100% alcohol either, and even witch hazel has some water in it as well, but what I was saying was that I don't use 100% water, as in distilled water as the liquid.

You can get what is called "Anhydrous Isopropyl Alcohol (Isopropanol)". It's 99% pure, with only 1% water, since alcohols are so hygroscopic in nature.
It's expensive however, around $39 per gallon on Amazon or $17-18 per quart on other websites. That pure type of isopropyl alcohol is normally used for laboratory uses or cleaning purposes such as degreasing electronic items as circuit boards, etc. 91% is quite sufficient and the small amount of water is negligible in that amount.

 

[earlene]

You can get what is called "Anhydrous Isopropyl Alcohol (Isopropanol)". It's 99% pure, with only 1% water, since alcohols are so hygroscopic in nature.
It's expensive however, around $39 per gallon on Amazon or $17-18 per quart on other websites. That pure type of isopropyl alcohol is normally used for laboratory uses or cleaning purposes such as degreasing electronic items as circuit boards, etc. 91% is quite sufficient and the small amount of water is negligible in that amount.

I did look into that some time ago to use when I was replacing a heat-sink in my laptop. At the time, however the alternative 91% was acceptable according to computer repair sources I contacted, so that is what I used since there was no where locally I could find 99% IPA.

However, now if I felt it was a cost benefit, I could purchase it for $24.99 per gallon at a nearby Ace Hardware. And only $17.12 per gallon at Walmart (online order). But I still don't feel it is a cost benefit. I would not buy it for use to make the odd Bath Bomb (I only make them for my granddaughter) and I don't need to do a whole lot of computer repair these days.

 

[Rsapienza]

I would assume the water evaporates out, being that I’ve never heard of anyone using a preservative in bath bombs. I live in FL where it’s pretty humid, and I spray my mix with water to bind. It’s the only way they seem to work for me. They dry rock hard within hours.