Solid Dish Soap Bar Recipe: How to Make a Zero Waste Dishwashing Soap

Learn how to make a zero waste dishwashing soap bar. An eco-friendly solid dish soap bar recipe will not only help to save money, it also reduces waste and your impact on the environment. Like you’d expect from a liquid dish soap, this cold process dish soap recipe gives you plenty of suds, and it cuts through grease to thoroughly clean your dishes. Learn about the different methods for making solid dish soap at home to help you cut costs while also helping the environment. Plus why I prefer to make a cold process dishwashing soap to other soap making methods.

Why Should I Use Solid Dish Soap?

There are two constants in life: dishes and laundry. Okay, so there’s a third one, taxes, but I digress.

Doing the dishes isn’t my favorite task. Sure, I can run the dishwasher for most dishes, but sometimes I don’t have enough dishes or I have dirty dishes that can’t go through the dishwasher.

Since I’m a DIY kind of girl, I’ve made several homemade dish soap recipes. I had just about given up on an effective, sudsing homemade dish soap when I made this solid dish soap bar.

We’ve gotten so used to using liquid dish soap that my mind got stuck on making a liquid dish soap. Since I’m a cold process soap maker, I thought why not make a solid dish soap recipe? Success! I finally found a homemade dish soap that works and gives me the suds that I like. It also does an incredible job at cutting grease.

As a soap maker, I know that we don’t need suds to get clean. Soap suds are more for visual appeal than for actual cleaning. Soap suds are nothing more than soap molecules trapped in round air pockets. That air doesn’t clean, obviously, but it’s a visual cue that the soap is there.

Even though I know that suds do not equal cleaning, I still like seeing the suds when I’m doing dishes. It helps me know that I’m using soap, and that soap is cleaning my dishes. It’s purely psychological, but I’ve found that many people feel the same way that I do about their soap sudsing when they use it. This solid dishwashing soap not only gives me the suds I expect, it really does clean my dishes, regardless of how hard my water is here in Southwestern Virginia. 

But why should I make the switch to a solid dish soap? There are three great reasons for this. Solid dish soap is eco-friendly. It’s also about as close to zero waste as you can get for a dishwashing soap. Which is important considering how much plastic pollutes our environment on a daily basis. It also saves money. So if you’re looking for a frugal way to cut household cleaning costs, this is a great way to get started.

What Makes Solid Dish Soap Eco Friendly?

Solid Dishwashing Soap Reduces Plastic Waste

As a society we create an enormous amount of waste in our day to day lives. Plastic waste is the worst culprit. As it doesn’t biodegrade — it takes over 400 years for plastic to degrade — it ends up not just in our landfills, but it also ends up in our oceans. And it’s a lot more than you might think. In fact, plastic waste currently covers 40% of our oceans, causing both ecological damage and harm to wildlife.

While recycling programs do exist, 91% of plastic is not recycled. If you consider how much plastic we use in our everyday lives, from shampoo bottles to dish soap containers and other cleaners, that’s a LOT of plastic. Even our disposable toothbrush handles and disposable straws are made from plastic.

Here are some of the many reasons why we should work to reduce plastic waste.

• 91% of all plastics are NOT recycled.

• 5.25 trillion pieces of marine trash have ended up in our oceans.

• 90% of all seabirds have eaten plastic. This up from just 5% of seabirds in 1960.

• Between 2000 and 2010 we made more plastic than all the plastic in history up to the year 2000.

• Plastic doesn’t biodegrade. The EPA reports that “every bit of plastic ever made still exists.”

• Marine animals both ingest and get tangled up in plastic. This can lead not just to injuries but also painful deaths.

• By 2050 the ocean will contain more plastic by weight than fish.

• Americans use 500 million plastic straws everyday. That’s enough to circle the Earth twice.

Luckily there are a number of ways to reduce plastic use. Making and using a solid dishwashing soap is one of those ways. Solid dish soap bars don’t require any packaging. So there about as close as you can get to being a zero waste product. While nothing is truly zero waste — we rely on packaged materials to make most products — it does significantly reduce the amount of waste we create. It’s also more economic to use solid dish soap bars in the long run. Thereby we not only help the environment, we can also save money.

Solid Dish Soap Can Reduce Palm Oil Use

Palm oil is in so many products we use everyday. It can be found in Crisco and peanut butter, bread, chips, soy milk and even soaps. In fact, it’s sometimes hard to located products that don’t contain palm oil, which is often coined as vegetable oil. Manufacturer’s love palm oil because it’s cheap. Unfortunately, its use harms the environment in a number of ways.

While there are numerous articles on the devastation the use of palm oil causes, these are the basics.

• It’s destroyed 3.5 million hectares of rainforest throughout Indonesia, Malaysia, and Papua New Guinea.
• The slash and burn agricultural process used to clear the land continues to burn the peat and other organic materials on Rainforest floors — even after the fires have been put out.
• The burning of Rainforests results in air pollution, which is sometimes toxic, and effects and affects health of those living in the area and contributes to global warming.
• Deforestation to grow and harvest palm oil threatens the habitats of endangered animals like orangutans and Sumatran tigers.

Therefore, by formulating and creating a solid dish soap bar without the use of palm oil, you can further reduce your impact on the environment, and create a more eco-friendly cleaning product. (Learn more about using palm oil in soap making.)

How Do I Make a Solid Dish Soap Bar?

What’s the Best Method for Making Dish Soap?

There are a number of ways to make a solid dish soap. This methods include various soap making methods such as hand-milled soap, melt and pour soap and cold process soap. There are also a number of formulations you can try that call for using surfactants instead, such as this solid dish washing brick.

While using a pre-existing soap base to make a solid dish soap bar is an easy way to get started, this method does have limitations. When you start with a pre-existing base, such a melt and pour soap base, you are hindered in fully customizing your final product. For starters, you can only add a certain number of ingredients to a melt and pour soap base before it starts to inhibit the lather.  Likewise, while coconut oil is often added to cold process soap to increase the lather, as melt and pour soap does not go through the saponification process, it is unable to increase lather with its addition. It may make the soap more hydrating, however, hydrating is not want we want for sparkly clean dishes. It’s also often hard to avoid the use of palm oil, which is commonly found in most melt and pour soap bases.

Using surfactants is another option for making solid dishwashing soap. There are a number of gentle surfactants on the market today that can be combined with other ingredients such as washing soda to help it cut grease. However, not all surfactants are created equal. Not only is it possible they may irritate skin, they can also be more costly to procure. In addition, there is some concern that they may harm marine life depending on the product and amount used. Further, when making a surfactant based dish soap bar, a preservative is also required, thus adding to the cost of the final product. Not to mention, surfactants aren’t really an eco-friendly ingredient. They are typically made using fossil fuels, and even surfactants claiming to be eco-friendly are often created using palm oil, or derived from some form of palm oil.

A more economical, and eco-friendly, way to make solid dishwashing soap is to create a dish soap bar recipe from scratch using the cold process soap making method. While making cold process soap may seem scary at first, it’s actually easier than you might think. (I personally freaked myself out about using lye for years before I finally took a plunge.) This way of making homemade dish soap bars allows you to customize a solid dishwashing soap from the very beginning. So you not only save money, but you get a product that has all of the properties you want in a dish soap, and none of the ones you don’t.

If you still aren’t comfortable making cold process soap from scratch, not to worry. Another alternative for making homemade dish soap is use an existing cold process soap bar or a rebatch soap base. These types of soap tend to retain their ability to lather better than most melt and pour soap bases, which are formulated for use on skin and aren’t equipped to handle a lot of additives. By hand milling or rebatching an existing soap, such as a 100% coconut oil soap, and adding similar ingredients to my cold process dishwashing soap bar recipe, you can still create a dishwashing product that yields similar results. (I’ll be covering this process in another post.) Alternately, Life-n-Reflection has a super easy recipe for making a melt and pour solid dish soap.

What Are the Best Ingredients for Dishwashing Soap?

All soap making oils have different properties when used to make cold process soap from scratch. Once saponified, these properties become evident. Some soap making oils help create a hard bar while others are extra cleansing, give soap a fluffy lather, a stable lather, or add skin conditioning properties. Therefore, choosing which oils to create a solid dish soap bar does matter. You want your solid dishwashing soap to clean your dishes but not totally destroy your hands in the process. This can be a delicate balance.

Coconut Oil

Most soap making oils help to produce a stable lather and offer some level of conditioning. There are a few oils that don’t add any skin conditioning properties to soap when making cold process soap. Those oils include babassu oil, coconut oil, cottonseed oil, palm oil and palm kernel oil. As I wanted my solid dish soap bars to be palm free, I opted for using coconut oil as the main ingredient in my dishwashing soap recipe.

The properties of coconut oil in soap making are as follows:

• Produces a hard soap bar.
• Creates a cleansing soap.
• Gives soap a fluffy lather.
• Results in a quick trace.

As coconut oil is highly cleansing, it is often used for natural cleaning recipes, including homemade laundry stain removers.

If you are allergic to coconut oil, you can use babassu oil in its place. It has the same soap making properties as coconut oil, and therefore makes a suitable swap. However, you will need to run my solid dish soap bar recipe through a lye calculator if you need to make substitutions or resize the recipe. (Learn how to use a lye calculator to make cold process soap or change a recipe.)

Castor Oil

Where coconut oil produces a highly cleansing soap bar with a fluffy lather, it does not yield a stable lather. Coconut oil soap also offers no skin conditioning properties unless you use an incredibly high superfat. (The standard superfat for most homemade soaps is considered to be 5%, whereas for a 100% coconut oil soap you’d want to increase the amount to 20% to avoid stripping skin of its natural oils. You can learn more about how to make cold process soap and understanding superfatting in soap making here.)

In order to add some stability to the lather of my solid dish soap bar, I therefore add castor oil to my solid dishwashing soap recipe. Most soap makers add castor oil to soap to create more bubbles. Castor oil also offers some level of skin conditioning, though not so much your dishes don’t get clean.

The soap making properties of castor oil are:

• Produces a stable lather.
• It has skin conditioning properties.
• Results in a quick trace.

Lime Juice

Like all cold process soap, you need both fats and an alkali to make soap. The fats in my solid dish soap bar recipe are the coconut and castor oils. The alkali, is the lye or sodium hydroxide. A liquid, however, is required to dissolve the lye before you mix it with the fats, or soap making oils or butters you’ve chosen for your recipe. This is commonly water, however, you can also use cow or goat milk, coconut milk or another liquid of your choice. 

As I wanted to develop a solid dishwashing soap bar that not only got dishes clean, but also helped to cut grease, I substituted part of the water in my solid dish soap recipe with lime juice. Limes are naturally acidic, so they work they work to naturally kill germs. Lime juice is also a great grease fighter, so it can remove grease on your dishes.

(Based on feedback from several readers, you cannot substitute lemon juice for the lime juice in my solid dish soap recipe. I also recommend using fresh squeeze lime juice unless you can source lime juice that has nothing added to preserve the freshness of the product.)

Citric Acid

I also added citric acid to my solid dish soap recipe for its natural cleansing benefits. Citric acid naturally kills bacteria, mildew, and mold. This makes it a wonderful, all natural disinfectant to use when washing dishes. Additionally, citric acid also removes hard water spots, lime, rust, and soap scum. Therefore, if you have hard water, you’ll definitely appreciate the citric acid in my solid dishwashing soap recipe.

Citrus Essential Oils

For a natural scent, I used lime essential oil and mandarin essential oil. Not only does it smell great, but both scents are uplifting and refreshing. Lime is a natural degreaser, so it also helps remove stubborn grease from dishes. Mandarin essential oil not only smells great, but it’s also a natural antiseptic.

There’a a lot to learn about essential oils in soap making as different essential oil have different usage rates. These usage rates also vary based on the application. Lime essential oil can be use at a maximum of 25% of the oil weight in soap. While mandarin essential oil has a max usage rate of 5%. I chose to used these essential oils at a 2.5% usage rate (or .4 oz. per pound) for the two combined. Therefore, if desired, you can increase the amount of essential oils used to 5% for this dishwashing soap recipe by doubling the amount called for in the recipe.

It is important to keep in mind, however, that some essential oils do have lower usage rates than the ones I chose for my cold process soap recipe. Therefore, if you decide to swap out the essential oils I used for my solid dish soap bars, then be sure to refer to your supplier on safe usage rates in soap. It’s also important to note that not all essential oils are considered skin safe, even when diluted. You can learn more about how to safely and confidently use essential oils via Simply Earth’s Essential Oil Hero Course here.

Now that you understand about why I chose the ingredients I used to create my dishwashing soap, here’s my solid dish soap bar recipe so you can make your own! (This recipe does contain 1% superfat which equates to about 10% superfat in the final bar to negate some of the harsh cleansing properties of coconut oil on skin. For reduced superfat levels in the final bar after the acids, see the tips for hard water section below.)

Solid Dish Soap Bar Recipe

Yield: Around 3.06 lb. before the cure (plus the weight of citric acid & zest)

Ingredients:

3.2 oz. castor oil (10%)
28.8 oz. refined 76° melt point coconut oil (90%)

8.5 oz. distilled or filtered water (33% of oil weight when combined with lime juice)
5.6 oz. sodium hydroxide/lye (1% superfat)

2 Tablespoons citric acid
2 oz. lime juice, from 2 limes
2 teaspoons lime zest, optional
.6 oz. lime essential oil
.2 oz. mandarin essential oil

Tools & Materials:

Digital scale
Non-aluminum heat safe containers
Immersion blender
Silicone soap molds
Glass measuring cup
Measuring spoons
Thermometer
Spatula

Soap Making Notes:

Soap Making Molds for This Project

I recommend using  silicone soap molds with individual cavities for my dish soap bar recipe rather than a loaf soap mold. This will help prevent your soap from overheating. It will also give you bars that fit inside a kitchen soap dish. I used two separate molds when making my solid dishwashing soap to illustrate options for use. This recipe yielded a combination six flower shaped soap bars using the larger of these silicone molds and seven round dish soap bars from this round silicone soap mold. You can, of course, use any soap making molds you like. But you will need molds that can hold just over 3 lbs. of soap.

Cautions on Not Using Pyrex Glass Measuring Cups for Mixing & Heating

In addition, I do not recommend using any Pyrex for this project as it has been known to explode. (Apparently this is only an issue with newly produced Pyrex and not the vintage Pyrex which was made differently.) This typically happens when it is being heated.

Unfortunately, I recently had this experience and I wasn’t even making soap. In fact, I had just placed nested Pyrex measuring cups (2 quart, 1 quart and 1 cup) in the floorboard of my car for transport as I have many times before. My car was not at all hot. As I was driving down the road, the bowls rattled a bit. No more than they usually do when I take them down from a shelf or out of the cabinet. The second time they rattled, the largest of the Pyrex exploded. It didn’t break, it literally exploded. (Ignore the wine bottle. I bought it to make infused vinegar. Isn’t it pretty?)

Now you may be thinking what I’d first considered. That the Pyrex simply broke into pieces. Upon close inspection, however, it was clear this was more than a glass bumping into something and breaking. The damage was such that it appeared someone had stood in a chair and slammed the container onto concrete. The handle, which is super thick, looked like it had been cracked apart and glued back together. So yes, most assuredly, my Pyrex exploded. I’m just thankful it didn’t happen as I was taking them down from a shelf…

Information on How to Safely Make Cold Process Soap

My solid dish soap is made using the cold process soap making method. If you’ve never made soap using this method, you can learn how to make cold process soap here, as well as find advice and important safety tips. As lye, or sodium hydroxide, is caustic, you do need to take care when making soap. This includes wearing eye protection, gloves and avoiding use of any and all aluminium containers, molds and utensils. (When you combine aluminium and sodium hydroxide they react to form salt and hydrogen gas. Hydrogen gas is extremely dangerous and can eat through metal. So please check all your containers carefully.)

Directions on How to Make Solid Dishwashing Soap Bars Using the Cold Process Soap Making Method:

Using a digital scale, start by weighing out the coconut oil for the solid dish soap recipe. Place into a heat safe container, such as a non-aluminum stock pot. 

Then weigh out the castor oil and add to the container of coconut oil.

Heat the coconut and castor oils over medium-low to medium heat until melted on the stovetop in a stainless steel pot. Once melted, remove the oils from the heat and set aside to cool.

In the meantime, measure out the water into a separate heat safe container. (You don’t want to use Pyrex to mix the lye, therefore a stainless steel pitcher or heat safe plastic container is recommended for mixing.) Then, using a third container, weigh out the lye.

Slowly pour the lye into the water in a well ventilated area. Mix well to combine, until all of the lye has dissolved. Set the lye-water aside to cool.

Now, measure out the lime juice into a glass measuring cup. Measure out the citric acid using a measuring spoon and mix into the lime juice into it dissolves.

Weigh out the essential oils next. Then stir them into the lime juice and citric acid mixture. Set aside.

Once the lye-water and the melted oils both reach a temperature of around 100°F to 110°F, you’re ready to make your solid dish soap. (Ideally you want both the lye-water and soap making oils to be within 10°F of one another.)

Remix the lime juice, essential oil and citric acid mixture with a utensil. Then pour it into the soap making oils. Add the lime zest.

Now mix them all together using an immersion or stick blender until fully incorporated.

Carefully pour the lye-water into the soap making oils. Then mix with the immersion blender until you reach a light to medium trace. (You’ll know you’ve reached trace when you drag your blender across the top of the soap and it leaves a trail behind it. It will be similar to the consistency of pudding.)

Working quickly, pour the soap into the molds of your choice. Use a spatula to smooth out the tops. (This soap will trace and set up fast. So have those molds ready to go!)

Allow the solid dish soap bars to set up in the molds overnight. You can then unmold your solid dishwashing soap bars the next day.

Once you unmold the solid dish soap, allow your soaps to cure in a cool, dry location over a period of four weeks prior to use.

Once your solid dishwashing soaps have cured, they are ready to be used!

Tips for Hard Water: If you have hard water and need extra bubbles, you can safely increase the amount of lye to 5.85 oz. This reduces the final superfat to 5% when taking the acids in the recipe into account. While the final bar will not be lye heavy, it will have additional cleansing power that may be overly harsh on skin as it will strip skin of its natural oils, especially when you consider coconut oil’s extremely high cleansing properties.

Alternately, you may also use 6.1 oz. of lye for an end superfat of about 1% after the acids. (Please run the recipe through a lye calculator that includes acids to double check these numbers if you have access to one when reducing the superfat to this percentage to avoid a lye heavy bar.)

How to Use Zero Waste Solid Dish Soap Bars

I grew up watching my mom fill the sink with hot water and squirting in dish soap to create a mound of bubbles. With each dish that she added, washed, and rinsed, the water got cooler and the suds got fewer. Eventually, she was left with cold water with barely any soap left.

You’ll use this solid dish soap bar a little differently. Instead of filling the sink with hot, soapy water, simply soak an eco-friendly sponge with hot water. Then rub it over the solid soap, and wash your dishes. When the sponge runs out of soap, rub it over the soap and keep cleaning. This solid dishwashing soap works wonderfully with these eco-friendly walnut scrubber sponges. (Learn how you can get these sponges, and an eco-friendly cleaning set, free here.)

Alternately, you can also use a palm scrub brush or wet cleaning scrubber as you ordinarily would. However, instead of the filling the soap dispenser with liquid soap, you’d simply drop in your solid dish soap bar. This bubble up dish soap dispenser and brush set pairs perfectly with solid dish soap bars.

There’s also a third way to use this homemade dish soap bar: as a powder. If you prefer to fill up a sink with hot water so you can let dishes soak for a while, or just like doing dishes that way, you can turn this solid dishwashing soap into a powder. Since it’s a low moisture soap, it will grate well. Just grate a bar into a fine powder and add a tablespoon under the hot water as you’re filling the sink. It will create a sink full of suds and works well to get your dishes clean.

Yield: About 3 lbs.

Solid Dish Soap Bar Recipe

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Learn how to make an eco-friendly, zero waste solid dish soap bar recipe to naturally clean your dishes. This cold process dishwashing won't harm the environment and also reduces plastic waste in your daily cleaning routine.

Prep Time 10 minutes

Active Time 15 minutes

Additional Time 1 hour

Total Time 1 hour 25 minutes

Materials

• 3.2 oz. castor oil (10%)
• 28.8 oz. refined 76° melt point coconut oil (90%)
• 8.5 oz. distilled or filtered water (33% of oil weight when combined with lime juice)
• 5.6 oz. sodium hydroxide/lye (1% superfat)
• 2 Tablespoons citric acid
• 2 oz. lime juice, from 2 limes
• 2 teaspoons lime zest, optional
• .6 oz. lime essential oil
• .2 oz. mandarin essential oil

Tools

• Digital scale
• Non-aluminum heat safe containers
• Immersion blender
• Silicone soap molds
• Measuring spoons
• Glass measuring cup
• Thermometer
• Spatula

Instructions

1. Weigh out the coconut oil and castor oil. Place into a non-aluminum stock pot. 
2. Heat the soap making oils over medium-low to medium heat. Once melted, remove from heat and set aside.
3. Measure out the water into a separate heat safe container. Then, weigh out the lye and add to a third container.
4. Pour the lye into the water. Mix until all of the lye has dissolved. Set aside to cool.
5. Measure out the lime juice into a measuring cup. Measure out the citric acid using measuring spoons and mix into the lime juice into it dissolves.
6. Weigh out the essential oils, then stir them into the lime juice and citric acid mixture. Set aside.
7. Once the lye-water and the melted oils have cooled to around 100°F to 110°F, you’re for the next step.
8. Remix the lime juice, essential oil and citric acid mixture with a utensil. Add the lime zest. Then pour it into the soap making oils.
9. Mix them together using an immersion blender until fully incorporated.
10. Pour the lye-water into the soap making oils. Mix with the immersion blender until you reach a light to medium trace.
11. Pour the soap into the molds of your choice. Use a spatula to smooth out the tops.
12. Allow the solid dish soap bars to set up in the molds overnight. Then unmold the next day.
13. Allow your soaps to cure in a cool, dry location over a period of four weeks prior to use.

Natural Cleaning Products You Can Make At Home

If you like my zero waste recipe for making solid dish soap bars, then you may also enjoy these eco-friendly cleaning tips using natural, non-toxic cleaners. Or try one of my other homemade cleaner recipes for natural cleaning products.

• Vinegar Free All Purpose Cleaner Recipe
• Deodorizing Room Spray Recipe with Essential Oils
• Stain Remover Recipe for Laundry Stains
• Natural Soft Scrub Cleaning Clay Recipe
• Homemade Laundry Detergent Recipe
• DIY All Purpose Cleaner with Essential Oils
• Homemade Floor Cleaners for Mopping

For more natural ways to clean your home and other homemaking tips and tricks, be sure to follow me on your favorite social media platforms. You can find me on facebook, twitter and instagram, as well as on Pinterest and Blog Lovin‘.