The best lye for soap making is 99 percent pure, food-grade sodium hydroxide in pellet or bead form. Purity and food-grade ratings ensure the lye contains fewer impurities. Beads and pellets make it easier to measure. However, potassium hydroxide (not technically lye) is best for making liquid soap.
For most projects, this type of lye, found on Amazon, will work very well. It is food-grade and made in the USA.
This article delves into the differences between sodium hydroxide and potassium hydroxide and lists the five best lyes for soap making. Toward the end, I’ll discuss where to purchase lye (aside from online retailers) and what safety precautions you should follow when working with the caustic substance.
Sodium Hydroxide vs. Potassium Hydroxide for Soap Making
Soap making initially involved wood ashes and animal fats, resulting in a mushy, dark-colored substance. Today, manufacturers use a similar process for liquid soaps, using potassium hydroxide and fats such as shea butter, coconut oil, and palm oil. For bar soap, however, companies utilize sodium hydroxide — also known as lye — as the primary ingredient.
Before jumping into the best types of lye for soap making, you must understand the difference between these two commonly used ingredients. No matter which chemical you choose, you’ll end up with a soap that lathers and cleans. However, each substance creates a different type of soap (solid bar soap and liquid soap) with its own look and feel.
Because of this, you must know which ingredient to use depending on the type of soap you intend to make.
Sodium Hydroxide
Sodium hydroxide is true lye, also referred to as caustic soda. Its chemical name is NaOH. It’s the most common saponification ingredient used in soap making and results in a solid block of soap. Hardening happens due to the saponification process (when mixing lye with fat) because the substance crystallizes. Soap made using lye may be formed using molds or cut into bars or other shapes.
Most pure lye is white, allowing for the addition of dyes without diluting the hue. However, some lye may be off-white, yellow, or gray.
When purchasing sodium hydroxide, ensure that the product is 99 percent pure and in the form of pellets or beads. Purity ratings of 99 percent are essential because they ensure there are no unwanted additives.
Most soap makers prefer pellets or beads, as they’re easier to measure and produce far less dust. Static electricity often causes coarse powders or flakes to get everywhere, leading to a potentially dangerous situation, especially in homes with children or pets.
As an added note, food-grade lye is traditionally preferred for bar soap making. It undergoes an additional purification process, removing more impurities than technical-grade lye. With that said, technical-grade lye still works in soap making — it’s truly a matter of preference. Keep in mind that food-grade sodium hydroxide tends to be more expensive than the technical-grade version.
Potassium Hydroxide
From a technical standpoint, potassium hydroxide (KOH) is not truly lye at all, nor do soap makers use it in the production of solid bar soap. If you attempt to use potassium hydroxide to make bar soap, you’ll end up with a gooey, sticky mess that doesn’t harden. Potassium hydroxide simply cannot create a solid product. Therefore, it’s only used in the production of liquid soaps and body washes.
As mentioned previously, early soap makers used ashes and animal fats. Interestingly, wood ashes produce potassium hydroxide, which is why potash creates more “authentic” soaps — meaning they’re closer to the original soaps made long ago.
Back then, soap makers often used salt to firm up the liquid, but it never formed the hardened blocks of soap you buy in stores. Today, some soap makers use hard fats to make bar soap with potassium hydroxide, but the curing time is significantly longer than with sodium hydroxide and the bars turn out softer. This is because potassium hydroxide does not crystallize.
When purchasing potassium hydroxide, look for products that mention food-grade to ensure you’re receiving a product with fewer impurities.
Best Lye Products for Soap Making
| Product | Pros | Cons |
|---|---|---|
| 1. Essential Depot Sodium Hydroxide | *Available in bulk *Micro-pellets *White *Food-grade *99 percent pure | *Bottles aren’t vacuum sealed |
| 2. ComStar Pure Lye | *Bead formula *99 percent pure *Non-clumping *Pure white | *Not available in bulk *High price point for the amount |
| 3. Maxtite Sodium Hydroxide | *Available in bulk *Bead formula *Made in the US *99 percent pure | *High price point |
| 4. Quality Chemical Sodium Hydroxide | *Available in bulk *Bead formula *99 percent pure | *Off-white color *Technical-grade |
| 5. Belle Chemical Potassium Hydroxide | *Available in bulk *Made in the US *Food-grade *Child-safe jar | *90 percent pure |
1. Essential Depot Sodium Hydroxide
Due to the build-up of static electricity, sodium hydroxide flakes and powders tend to stick to their surroundings. Fortunately, the Essential Depot Sodium Hydroxide, available on Amazon, comes in evenly-sized pellets. As such, the product is less likely to cling to your surroundings and spread everywhere (thus, reducing the likelihood of dangerous situations).
Most soap makers also prefer pellets because they produce less dust and make measuring the product much easier with a food scale.
When purchasing Essential Depot Sodium Hydroxide, you’ll receive a bulk quantity of lye at a reasonable price point. Each order provides 32 pounds (14.51 kg) of sodium hydroxide. It arrives in 16 separate containers, each filled with two pounds (907 g) of the chemical. Some people find the multiple bottles inconvenient, whereas others prefer it for ease of use.
The plastic bottles come with child-resistant caps to prevent unwanted access. They’re resealable and BPA-free.
Essential Depot Sodium Hydroxide is food-grade, containing fewer impurities than other brands on the market. The color is pure white, making this an excellent choice for colored cold-process soaps, as it will not dilute or muddy your dyes.
2. ComStar Pure Lye
One of the best-selling soap-making products on the market, ComStar Pure Lye, offers industrial-strength sodium hydroxide with 99 percent purity. CornStar Pure Lye is pure white and therefore doesn’t dilute or mute colored soaps, allowing for more vibrant hues in the end product.
The solid lye comes in a spherical beaded formula, which most soap makers prefer over flakes or coarse powder. Beads, like pellets, make the sodium hydroxide much easier to measure out and work with. The beads rarely clump together the way that finer granules do.
This product is ideal for those who create soap in smaller batches. It comes in one-pound (454 g) containers. Because it’s not available in large quantities, purchasing a bulk amount of the ComStar Pure Lye tends to be a bit pricey.
3. Maxtite Sodium Hydroxide
The Maxtite Sodium Hydroxide, also available on Amazon, is 99 percent pure lye. As with all of the lye products included in this list, the Maxtite Sodium Hydroxide comes in beads, not flakes, powder, or granules. It’s pure white, making it ideal for dyed bars of soap.
It comes in a 40-pound (18 kg) tub. The sodium hydroxide arrives double-sealed, once in a plastic bag and again in the sealed plastic pail, to protect it from moisture. The product is manufactured in the United States.
4. Quality Chemical Sodium Hydroxide
The Quality Chemical Sodium Hydroxide (Available on Amazon) is the only technical-grade sodium hydroxide included on this list. Most soap makers prefer food-grade lye (due to the additional purification steps), and most manufacturers consider technical-grade sodium hydroxide perfectly suitable for soap making. It may not create a product as pure as food-grade lye, but it won’t affect the overall quality of the soap.
You’ll receive 40 pounds (18 kg) of caustic soda beads in a plastic pail for a reasonable price. It comes with a plastic bucket lid opener to make the container easier to open.
The one drawback to Quality Chemical Sodium Hydroxide is that it comes in an off-white color. It may not produce as vibrantly hued soaps as the pure white forms of lye.
5. Belle Chemical Potassium Hydroxide
Belle Chemical Potassium Hydroxide is the only potassium hydroxide formula on this list, particularly for liquid soap makers. It’s food-grade potash made in the United States, and it arrives in a durable, child-safe container.
It’s available in several package sizes, including:
- 1-pound (454 g)
- 2-pound (907 g)
- 5-pound (2 kg)
- 10-pound (4.5 kg)
- 20-pound (9 kg)
Unlike sodium hydroxide, the Belle Chemical Potassium Hydroxide does not harden, so it’s unsuitable for bar soap.
Where To Buy Lye for Soap Making
I’ve already listed four different types of lye and one type of potassium hydroxide for soap making, all of which are available on Amazon. In addition to online retailers, you can purchase lye in brick-and-mortar stores.
Below, I’ll provide other places where you can buy sodium hydroxide or potassium hydroxide for your soap-making needs.
Chemical Supply Companies
Most chemical supply companies carry sod