FAQs: Preservatives

In addition to reading through these FAQs, you can also learn more about preservatives by reviewing the information on this page.


Preservative Calculator

You can use this handy-dandy calculator to figure out how much preservative you need to add to your final project. You can use grams or ounces, but it does need to be a weight measurement.

It is best to include your preservative as part of the original formulation, as a percentage, by weight. This calculator adds the preservative on top of an existing formula, which isn’t ideal, but is a decent place to start. This will result in a slightly lower usage rate, but if you’re using the maximum recommended amount that should still be within the recommended range. For instance, if you calculate a 100g recipe at 0.5% that’ll tell you to add 0.5g preservative, which means your batch size is now 100.5g. The preservative is now technically present at 0.497%, which is pretty darn close to 0.5% and within the recommended usage range.

Remember, there is always more to preservatives than just the usage rate! Be sure to look at effective pH range, solubility, and anything other conflicts. For relatively foolproof preserving I recommend using Liquid Germall Plus as it has a broad pH range, is water soluble, and you won’t easily de-activate it. You should use Liquid Germall Plus at 0.5%; the recommended range is 0.1–0.5%, but since our home laboratories are nowhere near sterile, it’s best to err on the side of more. Don’t use more than 0.5%, though—more preservative is not better!

If you want to use something else, please check out this page/table detailing lots of different preservatives (with references!). That will give you the recommended usage rates for the second field, and details some incompatibilities or conflicts.



How do I know my preservative is working?

The two biggest ways you’ll know if your preservative is working are either the test of time (months and years), or a professional microbial challenge test (these typically run upwards of several hundred dollars per test, and still take some time get results).

For most home crafters who don’t intend to sell their products the cost of a professional test makes that option quite unappealing. So, we are left with time—and we all know that takes, well… time!

Here’s a few ways to increase the chances of our preservative succeeding:

  • Choose a preservative with a good reputation (do some googling and look for experiences with it that aren’t from the manufacturer). This often means sticking to preservatives that have been around for a while. New preservatives come out all the time (especially more natural ones), but if you’re looking to to avoid doing the initial leg work to see if they work well, you’ll have to wait until somebody else does it.
  • Check with your supplier to see what circumstances the preservative needs to succeed. pH, maximum allowable temperature, required usage levels, etc. Make sure you’re working within those parameters.
  • Use the maximum recommended amount, but no more.
  • Follow good manufacturing practice—keep things clean as you work.
  • Be aware of any more difficult to preserve ingredients in a formula; things like milk, clay, fresh fruits, etc. are really difficult to preserve. Keep in mind that more natural preservatives typically aren’t as strong as synthetic preservatives, so if you’re working with lots of harder to preserve ingredients you may want to choose a synthetic preservative instead of a natural one.

You can purchase at-home microbial testing kits as well, like this one from Lotion Crafter.

Found a new preservative that sounds promising, but you can’t find much on it? Try making a simple lotion using your new preservative, making sure you’re following the recommended usage rate, pH range, and any other pertinent requirements. Label it, and make note of your complete formula. Put the completed formula in a wide-mouthed jar and store it somewhere warm and bright (to encourage anything that might grow to grow faster). Wait, and see what happens. If it’s still looking good after three months, try making a more challenging lotion (something with perhaps 2% colloidal oatmeal) and add that to your experiment shelf.

If it’s still looking good after six months, shoot for a year. If it’s still looking good after a year, shoot for two. We can’t always see microbial spoilage, but if something still looks fine after a year, you can probably be reasonably confident it was ok at the six month mark. If you want even more information, get one of those at-home testing kits and test it every three months or so. See where it’s at!

Here’s a neat article on some ways to test stability at home.

I found this experiment from The Nerdy Farm Wife to be quite interesting reading!


Do I need to add a preservative to this recipe? How long will it last?

Short answers:

  • Does it contain water, OR will it come into contact with water, and do you intend to keep it longer than a day or two? Yes, you need a preservative.
  • If it contains no water, and will not come into contact with water, or if you’ll be using it immediately: No, you don’t need a preservative.

First off, there are two types of spoiling we’re worried about: rancidity and microbial (mould/fungus/yeast—living stuff).

Rancidity is a problem with oils, but it takes a very long time to set in. Oils, when kept somewhere cool and dark, will generally last years (though some are more shelf stable than others). You’ll know oil has gone rancid when it starts to smell off, sort of like very old lipstick or a bag of 10-year-old trail mix you found at the back of your pantry.

So, for things that are just made from different oils (body butters, lip balms, massage oils, etc.), rancidity is what you’re worried about, and you’ll generally have a few years before that sets in. You can delay it by adding an antioxidant like rosemary seed extract, grapefruit seed extract, or Vitamin E MT-50 (USA / Canada). I store yet-to-be-started lip balms and body butters in my fridge.

Mould and other bacterial spoilage become a problem when water (and time) is involved. That includes emulsions (like lotions), mists and sprays, and things that can be contaminated with water (like a scrub that lives in the shower). Ingredients like witch hazel, rose water, floral hydrosols, aloe vera juice, and milk still count as water when we are considering shelf life—in fact, they count as water plus additional bacterial temptation, and concoctions made with lots of these ingredients are harder (or in the case of milk, impossible) to preserve. The shelf life of something with water will depend greatly on how the concoction was prepared, how clean everything was, and how it is used and stored, so it is impossible for me to give you any kind of shelf life estimate. Generally speaking, though, things that contain water are probably only good for a day or two without a broad-spectrum preservative.

You MUST add a broad-spectrum preservative to recipes that include water. Broad-spectrum preservatives are not infallible, though—you can’t just add them to anything and expect it to last forever. Concoctions with lots of delicious bacteria food (herbal infusions, plant extracts, etc.) may eventually spoil regardless of added preservatives, especially because our kitchens are far from sterile. I make things in small batches, avoid as many temptations as possible, add a preservative, and watch for signs of spoilage, as I do with food in my fridge. If you notice changes in colour, scent, or texture, or you see mould or separation, it’s time to chuck it out.

Antioxidants like rosemary seed extract, grapefruit seed extract, and Vitamin E MT-50 (USA / Canada) are not preservatives and will do nothing to extend the shelf life of something that contains water and requires a broad spectrum preservative.

When it comes to selecting a preservative, make sure you read up on it to ensure it’s compatible with your product. Your supplier should list all this information on their website. Points to consider include:

  • Effective pH range: many more natural preservatives have a narrower effective pH range, so if you want to use them you will need to make sure you can accurately test and adjust the pH of everything you make to ensure your preservative is compatible.
  • Ingredient compatibility: some preservatives are inactivated by ingredients like PEGs or even vitamin C, so make sure you check and see what’s what/
  • Solubility: water-soluble is said to be best as anything that goes wrong in your product will go wrong in the water phase—that said, I have read a lot of debate on both sides of this. Whatever you do, make sure your preservative is soluble in your product (don’t put a water-soluble preservative in a 100% anhydrous product with no emulsifier)
  • Maximum temperature: don’t cook your preservative and ruin it. Preservatives typically go into the cool-down phase (below 40°C/104°F), but some products (like solid shampoo bars) are really dang solid at 40°C, so you’ll want to choose a preservative with higher heat tolerance (I like Optiphen Plus for this).

Trying to figure out how much preservative to add to your final product? I made a handy-dandy preservative calculator that you can use here.

Wondering which preservative to use? More on that here!


What preservative should I use? How much of it should I add?

If you are making something that contains water, you need a broad spectrum preservative. Imagine a tub of soup left out on your kitchen counter; how long would it have to sit there before you wouldn’t want to eat it anymore or serve it to company? That’s the kind of timeline we’re looking at for bacteria setting up shop in your watery concoctions.

There are a lot of broad spectrum preservatives readily available from DIY suppliers. Here’s a few:

  • Germall® Plus (powder or liquid)
  • Optiphen™
  • Optiphen™ Plus
  • Phenonip®
  • Leucidal® Liquid (not truly broad spectrum, but also not an antioxidant)
  • NeoDefend™
  • NataPres™
  • Gluconolactone & Sodium Benzoate

These things are often sold in the “preservatives” section but are not preservatives—just antioxidants. They are usually far less scary/more natural sounding, but they will not do the job at all.

  • Sodium lactate
  • Grapefruit seed extract
  • Rosemary antioxidant
  • Vitamin E

I encourage you to do your own research and decide for yourself which preservative will work best for you. I also encourage you to read everything about the preservative from the supplier to determine if it will work for you. Effective pH range and solubility are important things to consider. I’ve compiled a table of information about different preservatives here, complete with sources so you can read and learn more.

So, with all that in mind, for relatively foolproof preserving, I usually use Liquid Germall Plus. It is water soluble, effective in small amounts, and has a broad effective pH range (3–8). It’s not easily accidentally deactivated. You are unlikely to need to test the pH or adjust it. It has a usage rate of 0.1–0.5%, though I would recommend erring on the 0.5% of things for home use, since our kitchens are far from sterile.

The two active ingredients (Diazolidinyl Urea [and] Iodopropynyl Butylcarbamate) are a bit scary when you research them, but Liquid Germall Plus is 60% propylene glycol, meaning only 40% of your preservative is the scarier stuff, which means, at a 0.5% usage rate, only 0.2% of your formula will be “scary” ingredients. With the tiny inclusion of those scary ingredients, the rest of your formula will be protected from other scary things, like fungus and mould. In a 100g batch of lotion, that translates to 0.2g, which is barely anything, especially when spaced out over many uses.

Please see my Resources page for a list of links to places to purchase ingredients including preservatives.

How much do I need to use?

Each preservative will have a different recommend usage rate, which you can get from your supplier.

I made a handy-dandy preservative calculator that you can use here. Or, for the math:

Let’s say your preservative should be used at 1%; if your recipe contains 100g of ingredients, that’s approximately 1g of preservative. That’s not 100% accurate as 1% of 101g (original recipe + weight of the preservative) will be just over 1g, but with the small batches we’re working in the the accuracy level of the scales we’ve got at home, I consider it to be close enough.

  1. Figure out how much your recipe weighs. Either add up the weights of all the ingredients or weigh the final product.
  2. Figure out the recommended usage rate of the specific preservative you are using. Your supplier will provide this. Choose the higher end of the range since we’re not manufacturing in sterile labs.
  3. Multiply the weight of your product by the usage rate percentage, and divide that number by 100. So, if your concoction weighs 50g and the usage rate is 2.5%, that would be 50 × 2.5 = 125. 125 ÷ 100 = 1.25. That means you should add 1.25g preservative to your concoction.


Do I need to add a preservative to my soap?

If you are making your soap properly (that is, without a ridiculously high superfat percentage, and ensuring you’re measuring & calculating correctly)—no.

Soap has a high pH because it is made from lye, which has a very high pH. This high pH wards off bacterial growth. The high pH of the soap will not wear off over time.

If you superfat your soap much about 7%, you may encounter rancidity (the excess oils in your soap will oxidize) or DOS (deadly orange spots). The best way to avoid this is by not superfatting your soap above 7%.

Something else that can interfere with the shelf life of your soap is adding acid to lower the pH (I’ve read about people doing this for shampoo). I’ve never tried it myself, but logically speaking, lowering the pH of the soap means its pH may no longer be high enough to ward off bacterial growth.


On “antibacterial” ingredients

There are lots of ingredients out there that are touted to have antibacterial properties. These include things like honey, salt, and lots of essential oils and carrier oils.

While that’s all well and good, these things are not preservatives. Not even close. Honey, for instance, will last forever… on its own. If you mix it in some water and leave it out you’ll find it gets quite nasty, quite fast. Its antibacterial strength is in its purity, where its lack of water and high sugar concentration smothers bacteria. Once sufficiently diluted, this is no longer true. (The same is true for other syrups).

The same is true of salt; when used in high concentrations it’s a great preservative (used often to preserve meat), but you wouldn’t expect the teaspoon of salt you added to a batch of stew to preserve it indefinitely.

The gist of this is to say that just because something is antibacterial/has antibacterial preservatives on its own in no way means that it will bring those properties over to a final product in any meaningful shelf-life-extending way. That’s what broad spectrum preservatives are for.


Some common myths & misconceptions about preservatives

Whenever you’ve got water in a product, you need a broad spectrum preservative. Here are some common misconceptions about times when a preservative might not be necessary (spoiler alert… the preservative is still necessary!).

Ingredient X and ingredient Y have indefinite shelf lives, so when I combine them that mixture will also have an indefinite shelf life.
Ingredients like clay, honey, alcohol, and water can sit on shelves for ages and be fine, but this by no means translates to anything being made with them also having an indefinite shelf life! Think about flour, salt, water, and yeast—all will last for ages in their pure state when stored properly. Combine them into bread, and you will have a lovely loaf that will sprout mould in a matter of days.

Ingredient X has antibacterial properties, therefore it will preserve my entire final product.
No, it won’t. Once again, food is a great place to look for parallels. Spices like cinnamon, oregano, and cloves all have antibacterial properties, but you’d never make a curry with a cinnamon stick, store it at room temperature, and eat it a week later (I hope!). Ingredients with antibacterial/antiviral/antifungal properties are not broad spectrum preservatives. Please don’t try to use them as such!

Ingredient X is a store bought product that contains a small amount of preservative and since I am including that in part of a larger formula, I don’t need another preservative.
Proper preservation is not, unfortunately, contagious. The concentration of the preservative is very important, so when you dilute it, you weaken it and/or render it completely ineffective. Preservatives in store bought products are also carefully selected and blended based on the precise composition of that exact product, and that blend might not even work with the ingredients you’re working with. For a food metaphor; beef jerky has been preserved by smoking, but if you add it to a stew that stew can and will spoil!

Broad spectrum preservatives will prevent any and all spoilage for all eternity, regardless of ingredients, storage, and manufacturing methods.
Sadly, broad spectrum preservatives have their limits; especially when we’re working at home in less than sterile making environments. The more delicious bacteria food you add to your products (herbal infusions, food, milks, etc.), the faster they will spoil. Less than sterile making environment? Warm storage? Putting your fingers in things? All of those things will shorten the shelf life of your product, and while a broad spectrum preservative will help, it’s not infallible. Food analogy: consider (hypothetically or otherwise, haha!) putting the recommended amount of your broad spectrum preservative of choice in a pot of chili and leaving that on your counter for a few days. There is far too much bacterial temptation in that chili for the broad spectrum preservative to defend it, however valiantly it may want to. Erk!

I’ve also made a video on this topic, with even more myths! Watch it here.


How long will ______ last? What is its shelf life?

Long story short, it’s pretty impossible to give you an accurate answer to this, but I’ll try to help you determine a ballpark. Probably at least a year or two, but also “it depends, x1000”.

For 100% oil-based concoctions (lip balms, body butters, massage oils, etc.)

Because these things contain no water, we’re only concerned about rancidity—that is, the oils that make up the product oxidizing. You’ll usually get at least a year out of a 100% oil-based product, but that can be impacted by a few factors:

  • Storage. Cool & dark = longer shelf life. Warm & bright = shorter shelf life. (Store un-started projects, like extra lip balms, in the fridge before use for the longest shelf life.)
  • Ingredient freshness. Fresher ingredients = longer shelf life.
  • Ingredient shelf life. Some oils have longer shelf lives than others and will shorten the shelf life of your entire product. Check with your supplier to determine the shelf lives of your carrier oils (good suppliers should include a “best before” date on the carrier oils they sell). Examples of carrier oils with short shelf lives (generally less than a year) include flaxseed oil, borage oil, and evening primrose oil.
  • Added antioxidants. Adding an antioxidant like Vitamin E MT-50 (USA / Canada) or rosemary seed extract will help extend the shelf life of 100% oil-based products. Antioxidants are not preservatives!
  • Contamination. If you get water in a supposed-to-be-anhydrous concoction, it joins the second category in this list and the shelf life will shorten drastically.

For concoctions that contain water (lotions, body mists, creams, etc.)

Because of the presence of water, these projects can and will quickly sprout mould, fungus, and other gross things quite promptly without the inclusion of a broad spectrum preservative. Even with a broad spectrum preservative, these things can eventually spoil.

As with food, I would recommend that you are as clean as possible when making, avoid making more than you can use in a couple of months, and watch for spoilage (changes in colour, texture, scent, or mould population).

Here are some factors that will impact shelf life:

  • Inclusion of a preservative. If the formulation includes water (and the water will stay in the recipe and not be dried out of it) and is more than a single-use project (like a face mask), you need to include a preservative. Read this for more info.
  • The formulation itself. Some formulations are harder to preserve than others. The more bug food you include (aloe vera, botanicals, clay, honey, etc.), the faster the product can spoil. Preservatives will help extend that shelf life, but that shelf life is unlikely to be indefinite.
  • Freshness of ingredients. As with all things, fresher ingredients last longer. If you make a stew with nearly rotten meat, that stew will spoil faster than stew made with fresh meat. It is completely possible for an oil in your lotion to oxidize (go rancid) before bacterial spoilage sets in; short-lived oils like hemp seed and flax seed are definite candidates!
  • Storage. Cool & dark = longer shelf life. Warm & bright = shorter shelf life.
  • Cleanliness. Keep your kitchen and utensils as clean as possible while you’re making the project, and avoid contaminating it while using it (consider choosing pump-top bottles instead of open jars for lotions so you aren’t dipping dirty fingers into your final product).

So… how long will your product last? Sorry, but there are way too many variables to answer that question accurately. When I create and share a formulation I test it, and am reasonably confident my lotions and other water-containing formulations will be shelf-stable for at least 12–24 months. That said, that is for how I made (and stored) the formulation. Did you make a substitution or four? Did you package your product in a jar, while I used a pump-top bottle? Are you dipping your hands into your product directly after playing with your dog, contaminating it? Do you live somewhere drastically warmer than I do? Did you use mineral-rich well water instead of distilled water? All of these factors (and many more) can impact the shelf life of your product. With all these variables, it is flat-out impossible for me to give you an exact shelf life. Probably at least a year (but also please don’t spit in your formulations). Please read this for more information.

Trying to figure out how much preservative to add to your final product? I made a handy-dandy preservative calculator that you can use here.

For concoctions that contain water, but are dried out (bath bombs, clay bars, etc.)

If you’re making something that has water in it, but the water will be evaporated off promptly, you often don’t need a preservative. For something like bath bombs, they are dry for the vast majority of their life and are then used up all at once, so no preservative is needed and the shelf life should be more or less indefinite, assuming you keep it dry (if you live somewhere humid consider sealing the bath bombs in an air-tight bag).

For projects that will be continually wetted and allowed to re-dry, like a clay bar… this one is a bit tricky and depends on where you live. There are clay bars for sale which contain no preservatives, and while that’s not always a flawless indicator of best practices, one can assume that the company selling the bar does not want to sell a product that will sprout mould immediately. I live in a very dry climate, and have clay bars that I’ve used for years that have never shown any signs of spoilage as long as they’ve been left to dry between uses—but given the environment I live in, they always dry quite quickly. If you live somewhere humid, this may not be the case, and a broad-spectrum preservative may be advisable.

For Soap

Thanks to its high pH and low water content, bar soap should last for years. Using a higher superfat can lead to spoilage (look for orange splotches, also known as “dreaded orange spots”) or rancidity (too much unsaponified fat can go rancid in the bar).

Liquid soap paste will have a similarly long shelf life. Once diluted with additional water the pH should still be high enough to keep it from spoiling, but the final pH obviously depends on how diluted it is (more water = lower pH). You can also impact shelf life by adding lots of delicious bacteria goodies to your liquid soap (botanicals, clay, unsaponified oils, honey, aloe vera, etc.)—too much will impact the shelf life of your liquid soap. You can try adding a preservative if you are finding your liquid soap is spoiling quickly, but few are effective in high pH—from my reading, Liquid Germall™ Plus (INCI: Propylene Glycol, Diazolidinyl Urea, Iodopropynyl Butylcarbamate) would be your best bet.


How will adding ___________ ingredient impact the shelf life of my product?

To start with, there’s two main categories of product when we’re talking shelf life: things that are 100% oil based (lip balms, body butters, salves), and things that contain water (lotions, sprays) or might come into contact with water (body scrubs designed to be used in the bath).

For things that are 100% oil based

The kind of spoilage we’re concerned about here is rancidity, which is oils oxidizing and starting to smell funky (like old crayons). Some oils oxidize faster than others, so if you add an oil with a short shelf life (check with your suppliers, but anything less than one year is considered short), that will shorten the shelf life of your product. You can extend the life of 100% oil based products by adding an antioxidant, like vitamin E, during the cool down phase.

Adding anything that contains water (not just water, but hydrosols, teas, extracts, etc.) will bump your concoction to the other category and will drastically shorten the shelf life.

For things that contain water

Anything that contains water needs a broad spectrum preservative, but those are not infallible. The more delicious bug food we add to our potions, the faster we’ll override that preservative and the faster our products will spoil. Here’s a list of things that will speed spoilage (it is by no means exhaustive):

  • Any kind of food (milks, flours, starches, honey, syrup, sugar, nuts, etc.)
  • Any kind of plant matter (aloe juice, hydrosols, etc.)
  • All herbs and herbal infusions
  • Clays

Some of these things will spoil faster than others. Dairy milk is notoriously difficult to preserve and I would not recommend including it in anything that you don’t intend to use up that day. Clay masks are also very hard to preserve, so I would recommend only mixing the dry parts up in advance.

The amount of bug food you use is important, too. 1% honey is very different from 10% honey. If you want to include some oat milk or hydrosol in a lotion recipe, try replacing only half or a quarter of the water with it instead of all of the water.

You should also take a look at commercially produced herbal infusions and extracts rather than homemade to extend shelf life.

For things that could become contaminated with water

Honestly, the easiest thing to do here is to not allow the concoction to get wet. Scoop out however much scrub you need for a single use and take that to the tub in a small plastic dish. Put bath oils in pump top bottles. Use a dry finger or popsicle stick to remove cleansing balms from their containers.


If I don’t have a broad-spectrum preservative, what can I use instead?

Nothing. Seriously. There is nothing that will replace a true broad-spectrum preservative. If you do not have one, you should buy one, or you should only be making products that contain no water, otherwise you are risking infection from fungus and bacterial growth.

Remember, vitamin E and rosemary seed extract are in no way broad spectrum preservatives. They are simply antioxidants. A broad spectrum is something like Liquid Germall Plus or Phenonip. You can learn a lot about different preservatives here.


If I add one water containing ingredient to an otherwise water-free formula, do I need a preservative?

Yes. The inclusion of water always means you need a preservative unless the product is intended for immediate use. You will also need to incorporate an emulsifier in order to properly incorporate that ingredient into the rest of the product.

So, to recap, if you want to add something that contains water to an anhydrous preservative, you need to add:

  • The new ingredient
  • A suitable emulsifier
  • A suitable preservative

This is often more trouble than it is worth, so I’d recommend seeing if there is a water-free way to incorporate the ingredient you’re trying to add to the formula. If it’s a tincture, consider an oil infusion instead—that sort of thing.


What preservative can I add to lip products?

Both Geogard 221 and Geogard ECT are recommended for use in lip products by the manufacturer.

Anhydrous lip products (ones that don’t contain any water) shouldn’t need a broad spectrum preservative if kept dry.


Do I need to add a preservative to this if I plan on keeping it in the fridge?

Think of unpreserved DIYs that contain water like leftover food. How long would you leave a chili or a soup in your fridge before deeming it inedible? That’s roughly as long as you’ll be able to store an unpreserved DIY in your fridge—three to five days.

That kind of time span is generally not well suited to the sorts of products we make as even 50g (1.76oz) of lotion will usually take a couple weeks to use up.


Can I use a different preservative than the one you’ve used?


Different preservatives have different strengths and weaknesses, and different requirements for success that may or may not be compatible with the formulation. If you want to use a different preservative you’ll need to know what the new preservative needs, and if it is compatible with the formulation, or if the formulation can be made to be compatible.

You can learn more about the requirements of different preservatives here. If you don’t see the preservative you want to use listed, please refer to these blog posts (part 1, part 2) to learn how to research your ingredients and find that information.

Part of my development and testing process includes ensuring the preservative I include in the formulation is compatible with the formulation and works. If you’re changing up the preservative you’re using, you’ll need to do that testing work yourself. If you’re very familiar with your alternative preservative you’ll likely have a good feel for how it works; if it’s a brand-new-to-you preservative you’ll need to do more experimenting to get to know the preservative.

I also recommend giving this FAQ a read.

I’d also like to gently suggest that if an answer of “maybe” and “it depends” is not a sufficient answer for you, that you may not yet be at a level where switching around preservatives is in your wheelhouse. That’s ok, especially if you’ve been making for less than three years without any formal training. In that case, I recommend sticking with the recommend preservatives in formulations until you’ve learned more.


Why did my formulation spoil?

In the broadest sense, your formulation spoiled because some sort of microbes overcame your preservation system and are now having a party in your project, devouring all the delicious ingredients and making themselves a lovely little homestead. Ick!

There are quite a few reasons this could happen, but here are some of the more common ones.

You don’t include a preservative.

If your product contains water and isn’t designed to be used immediately, it needs a broad spectrum preservative. It’s also recommended to include one in anhydrous products that could or will come into contact with water, like a shampoo bar that lives in the shower.

The preservative you used was not well-suited to the formulation.

Different preservatives have different strengths and weaknesses that need to be considered when formulating, and not all preservatives work well in all formulations. Research your preservative and make sure it is suitable.

The preservative you used wasn’t actually a preservative.

Vitamin E, sodium lactate, and rosemary seed extract are three examples of ingredients that are sometimes sold as preservatives but aren’t. If you used one of these ingredients instead of a preservative, that’s likely the problem.

Something happened to de-activate the preservative.

Different preservatives have different requirements for maximum temperatures, pH, and more. Make sure you have not over-heated your preservative (leaving something like Liquid Germall™ Plus, with its maximum temperature of 50°C, in a hot car in the summer could be problematic), and make sure the pH of your formulation is appropriate.

There was so much contamination in the product that your preservative was overwhelmed.

There are many potential sources of contamination, including poor manufacturing process, ingredients, and the end user. Try reducing these sources by ensuring you are following good manufacturing standards, your ingredients are sourced from reliable suppliers, and packaging your products in a way that reduces potential contamination by the user.

As always—know your ingredients. Preservatives and preservation are massive, complex topics, and it’s important that you understand how your preservative works and what it needs to succeed. Different preservatives have different strengths and weaknesses that need to be considered when formulating. Here are some helpful resources to get you started on your research:


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