Preservative in aloe vera juice and converting % to drops

Oct 22, 2023 | The basics


Some time ago I’ve got a question from a reader asking about preservatives in water based products. And the main question was: how much of the preservative is needed for 8 oz bottles of aloe vera juice and how much that would be in drops?

Let’s dive into this question.


Firstly, I am happy that you know how important is a preservative, however the answer would not be very simple and depends on a lot of factors. That would be the initial product (here it would be aloe vera juice), the preservative itself and measuring your preservative.

As the goal is to preserve aloe vera juice, things are getting tricky here. One thing to know, is that aloe vera is hard to preserve and even though you can buy preserved aloe vera juice (hard to find though), you can get aloe vera in powder. Usually, aloe vera powder is used in cosmetics which is a lot easier to dose and contains a lot of nutrients. It is a concentrated powder that you can buy in 100x or 200x concentration.



When I got this question, I have started to think how where the aloe juice came from. Did it come straight from the leaves or had someone made it? Or are there plans to make juice from the aloe vera powder?

If you have aloe vera leaves, then I would advise you to sterilize your equipment first and make the juice (I am not familiar with the procedure). And use it directly on the skin. Keep the juice in refrigerator and use it within 3-4 days or freeze it (but some of the actives will probably be lost this way).

Making the juice from the leaves by yourself is a challenge and I am afraid that the microbial contamination cannot be avoided even when you are trying your best. This is why I would only use it directly on the skin and not make products with it. And use it quickly.

If you got already made aloe vera juice I would still use it in several days and keep it in the fridge.


However, if you are making aloe vera juice from the concentrated powder, make sure that the powder comes with minimal (within the appropriate range) or no bacteria in the first place. You should see this information in the Certificate of Analysis which should show that it has less than 100 cfu/gram or ml and no staphylococcus aureus, candida albicans or gram negative bacteria. This is very important for making other cosmetics with your made aloe vera juice.

In this case you would need a broad spectrum preservative that will protect the juice from bacteria and fungi. Still, even with the preservative, I highly suggest using this aloe juice quickly (3-4 months) and keep it in the fridge.



There are a lot of preservatives right now, but some are not the best ones even if the supplier or manufacturer says it is broad spectrum. Please do not use Naticide (INCI parfum), Leucidal Liquid SF, Leucidal Liquid, Leucidal Complete, Phytocide elderberry extract powder, Amticide Coconut, Phytocide elderberry OS. These are very poor preservatives and will not preserve your aloe vera juice.

Depending on what kind of preservative you want (natural, synthetic, nature identical) there are a lot of options. My go to preservative at the moment is Geogard 221 (which is not the best actually and I should change it to better preservative). But you can use any of these or your preffered preservative:

Sodium benzoate, potassium sorbate – soluble in water. Th pH should be below 5.5. This is actually the most widely used preservative for aloe vera juice.

Benzostat – INCI Caprylhydroxamic Acid (and) Benzyl Alcohol (and) Glycerin) – oil soluble. You will need a solubilizer.

Euxyl K940 – INCI Phenoxyethanol, Benzyl Alcohol, Ethylhexylglycerin, Tocopherol – has limited solubility in water. Solubilizer may be needed.

Liquid germall plus – INCI Propylene Glycol (and) Diazolidinyl Urea (and) Iodopropynyl Butylcarbamate – soluble in water.

Preservative 12, Euxyl® PE 9010, Ethox, GFpreserve POG – INCI Phenoxyethanol (and) ethylhexylglycerin – has limited solubility in water. Solubilizer may be needed. 

Each of these preservatives have a different usage rate, different pH that it is active and this should be taken to consideration. But they should work well to preserve aloe vera juice.



This is a checklist with essential equipment for making DIY cosmetics to help you get everything you really need.


I am against making a conversion from % to drops, though I can think of some reasons why. However, it is much easier and more accurate to use the scales and put the exact amount that you need as drops are not a good measurement. The drops differ in their weight and one time you may need more, other time you would need less.

One other thing, different preservatives have different density and you cannot use the same drop count for all preservatives. Also, different preservatives have different usage rate and knowing this, I cannot write the definite drop number for a preservative. The only answer how to make this conversion is to actually measure it.


The reasons why one would need to make this conversion is that the used scales are not that accurate, the scales are broken down or the scales sometimes freeze and don’t show the exact amount that you put. For all of these reasons I would suggest getting jewelry scales that can weigh up to 500 g or even a 1000 g (depending on your used equipment and batch sizes. If you have heavy beakers/bowls then get a 1000g scale) with 0.01 g increments.

Jewelry scales are usually quite cheap and they weigh quite precisely with very little issues. If you can, get the better scales with a plug (not with batteries). The best scenario is to get good scales from Kern, Ohaus or Sartorius, but these scales are on the higher end.


4.1. Calculations and conversion

If there is no possibility to get better scales and using drops is the only answer, I would suggest using the scales you have or borrow better scales from someone and do some tests.

But first, we need to do some calculations.

What we know is:

  • we are making 8 oz bottles of aloe vera juice from aloe vera concentrated powder
  • we need a preservative. Let’s say we are making two bottles of aloe vera juice with a different preservative. The first preservative would be Liquid germall plus and the second would be Euxyl K940. Liquid Germall plus has a usage rate of 0.5% and Euxyl K940 has a usage rate of 1%.
  • pH adjuster

Now we need to have the same measurements – we need to convert oz to grams and then to % in order to include the good amount of preservative.

8 oz is 226.796 grams. And now this our 100% that would also include a preservative. For the calculations I have made an excel file which helped me to convert it to the percentages, but the converted formula now looks like this:

99.5 % Water with aloe vera powder

0.5 % Liquid germall plus

q.s. Citric acid

And for the 226.796 g batch (8 oz batch): 

225.666 g | 7.9601 oz water with aloe vera powder

1.13 g | 0.0399 oz Liquid germall plus

q.s. Citric acid

With the Euxyl K940 preservative the formulation would look like this:

224.536 g | 7.9203 oz | 99 % water with aloe vera powder

2.26 g | 0.0797 oz | 1 % Euxyl K940

q.s. Citric acid

So now, when you have the calculations, you should make the product and measure the ingredients. When you are measuring the preservative, count the drops needed and write them down. For the best results you can make several batches and count the drops each time for every different preservative and write them down. And see if the drop count will differ.

For example if you made 3 batches with the same preservative and got the count: 34, 33, 34 (the drop count here is made up, please don’t use it), then just use 34 drops for that batch size.

If the drop count is more varied, such as: 30, 34, 29, then add all of those numbers and divide them by the batch numbers you made. Here it would be: (30+34+29)/3= 31 drops. And use this number for reference.

However, I strongly advise to get good scales and just use them, as using the scales will be more accurate and reliable. Please don’t use the drops as the main measurement.



Submit a Comment

Your email address will not be published. Required fields are marked *