How to Handle Potassium Hydroxide

When making soap from scratch, there’s one thing you just can’t avoid: lye. Without lye, your soap just isn’t soap! Working with lye may seem daunting at first, but if you learn proper handling techniques, take precautions and follow basic safety guidelines, there is no reason to fear it. You may be familiar with Sodium Hydroxide, which is used to make solid cold process soap, but today we’ll cover Potassium Hydroxide, which is used exclusively in liquid soap.  Although the rules for working with Potassium Hydroxide are similar to working with Sodium Hydroxide, it is important to understand and recognize the differences. Plus, it’s always nice to have a general lye safety refresher! To learn more on general lye safety, check out this blog post.

Potassium Hydroxide is a type of lye specifically used to make liquid soap. It is also known as potash, lye or even KOH. This is the chemical that induces saponification of the fats and oils to create liquid soap. Even though making liquid soap is different than making bar soap, it’s still vitally important that you use the correct amount of lye in your recipe. Our lye calculator makes this easy and allows you to select liquid soap as an option.

Potassium Hydroxide is hygroscopic (meaning it attracts moisture), so be sure to keep it in a sealed container in a cool dry place. If you leave it in an open container for even a day, it can attract enough moisture to throw off its weight enough to ruin a recipe.  If you leave it out for an extended period of time, it can attract enough moisture from the air in the room to turn completely liquid. When handling Potassium Hydroxide, give it the same safety considerations as you would with Sodium Hydroxide. It is a hazardous material, and being educated about safe handling practices is key when handling Potassium Hydroxide. As with any other type of lye, Potassium Hydroxide will emit some fumes, so be sure to soap in a well-ventilated area.

Always add your lye to your water, and never the other way around. Adding water to lye can cause a volcano-like reaction. Unlike Sodium Hydroxide, Potassium Hydroxide reacting with water makes a faint crackling or groaning sound — a somewhat subtle version of adding milk to Rice Krispies cereal.

When working with lye water, wear goggles that protect your eyes from all sides because alkali burns can cause blindness. If you wear glasses, check your local hardware store for goggles that are big enough to fit over them. Always wear an apron and gloves. Rubber dish gloves are great, but if they’re too bulky you can use thinner latex gloves.  Pair your gloves with long sleeves because the less exposed skin you have, the better. Finally, use a heat safe container to hold your lye water, and use silicone or stainless steel tools to stir (no wood). Never use any tools or bowls containing aluminum as that will create highly flammable hydrogen gases. Remember that when Potassium Hydroxide is mixed with water, it produces a reaction that heats the water up substantially, making it all the more important to mix lye in a heat safe container.

Never leave your lye water (or lye) unattended or in an place where children or pets may come in contact with it. It only takes a few seconds for an accident to happen! If you do need to leave the lye unattended for whatever reason, cover the container with a piece of plastic wrap and use a sticky note to clearly label it as a hazard.

If there is an accident:

If swallowed: Rinse mouth with water and drink one or two class of water. Do not induce vomiting! Immediately get medical attention or call your poison control center at 1-800-222-1222.

If in eyes: Immediately flush eyes with water. Remove any contact lenses and continue to flush eyes with water for at least 20 minutes. Immediately get medical attention or call your poison control center at 1-800-222-1222.

Lye water on skin: Wipe solution from skin and remove any contaminated clothing. Flush skin with plenty of water for at least 15 minutes and then wash thoroughly with soap and water. Contact a physician or call your poison control center at 1-800-222-1222.

Raw soap on skin: Even after it has been mixed with oils, lye can still be dangerous. If exposed skin comes in contact with raw soap batter, flush with water for 5 minutes and then wash thoroughly with soap and water.

Just like any tool, Potassium Hydroxide can be used safely and carefully to create wonderful liquid soaps for personal or business use. Use it responsibly.

What are you experiences working with Potassium Hydroxide? Let us know your best tips and tricks to work with it in the comments below!


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  1. Michelle says

    I cannot find information anywhere on Brambleberry concerning the purity of your KOH that you sell. I am assuming it is 100% because the most common other purity value is 90% — and in the latter instance it usually says so on the container.

  2. Kaitlyn says

    The protocol for first aid is wrong. Acid into water, never the reverse-this is as important for first aid as the soap! Using distilled white vinegar is a far more effective neutralizer than water. As always, do your own research before using any chemical. Consulting your local Poison Control as well as requesting the MSDS from the manufacturer for your chemicals is the safest bet. Happy (and safe!) soap making!

    • Kelsey says

      Hi Kaitlyn!

      According to our MSDS from the manufacturer, if the lye comes in contact with your skin, remove the affected area of clothing. Then, flush the skin with plenty of water for at least 15 minutes. Next, cover the irritated skin with an emollient. I’d be more than happy to send you a copy of the MSDS if you like. :)

      -Kelsey with Bramble Berry

  3. Christina says

    Like a commenter above, I’m wondering how you go about using both types of lye in a single recipe. I’m going to try a shaving soap in the next few weeks using both but not sure what the deal is. Would I just add both types of lye to the liquid and use the same process from there?

  4. Luzvi says

    I don’t have Potasium hydroxide in hand but I want A liquid hand soap, luckily I have soap batch that I don’t like. I grated them and melt like rebatching then when it turn paste I add boiling water with citric acid the I melt them for 6 hours in double boiler in just hot water below. It turn liquid soap. It’s a bit cloudy not like the normal liqiud soap but I like it, it’s gel well like normal liquid soap too.

  5. says

    Thanks for all the helpful info on your site, it is such a great resource! I am in the process of making shaving soap and was wondering what the method is for using KOH and NAOH in one recipe? I read somewhere that I need to use a 60/40 % ratio of the two, any suggestions/tips would be greatly appreciated. Greetings from Sunny South Africa…

  6. kaye kelvey says

    Made castile cold process soap using potassium hydroxide instead of sodium hydroxide by mistake. It finally traced poured in mold and after long time did get it cut with fishing wire, but mushy bars. Hasn’t hardened much. Should I throw them out or is there a way to salvage this soap? Been about 8 weeks since I made them.

  7. Sly says

    Thank you so much for this great information. I got some soap on my temple & cheek in the area not covered by my goggles & mask. I caught the one on my temple right away and immediately wiped it off & sprayed on vinegar, which really stinged & burned – and spread it around too (I should have washed it off more thoroughly).
    I didn’t notice or feel the soap on my cheek until 45 min later, after I finished soaping and cleaning up. I washed it off, but didn’t know that I should continue to wash for 15 minutes. My whole cheek – under where the bit of soap was – burned and puffed up for a week.
    What I could not find on the internet or from friends (non-Soapers) is what to apply to the burned area to help it heal (didn’t see that info here either). I tried Vit E – which burned, Aloe gel – which worked for a few hours before stinging, and I settled on Calendula Gel, which usually does a great job of helping to fast. However, I still ended up with a scar on my face.
    I agree with the first comment about how disrespectful so many Soapers are with using lye – they made me believe that lye burns were no big deal – but they really are!! Lye is dangerous! (On the other side, I am saddened when I read blogs from MP Soapers that are terrified of using lye. They are missing so much fun! I want to say to them to just respect the lye and it will be OK!)
    Thank you again for the great info!!

  8. says

    Whenever making liquid or bar soap we always keep a fine mist spray bottle filled with vinegar nearby as it helps neutralize lye. We spray all containers and tools that come in contact with the lye water solution after use and before washing and it saved me when a jar cracked one time after I added the lye to the water too quickly.

    Thanks for the tips! I too must buy my Potassium Hydroxide in bulk where I live but the humid climate it starting to affect its weight and throw off my recipe such that not all of the oils are saponifying. I now use only 1-3% superfatting rather than my standard 7%. The soap calculator makes this adjustment super easy to do!

    Great post!

  9. says

    Hi, I’m Chilean, excuse me I used the translator. I have had very good experiences using potash. The best results I get glycerin adding lye water to accelerate saponification. My last was potash soap shaving soap soda and potash mixture. I share and thank you very much for the post. Marcela

  10. Barbara D. says

    Thankyou for this! I have been soaping for over a decade now and it makes me cringe when I watch “instructional” videos on youtube from seasoned crafters and they are bare handed or even have toddlers and pets wandering around. Most accidents happen when you get sloppy or over confident.

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