Laundry soap mix
There are many recipes for dry laundry soap mixes on the internet. The recipes typically call for grating a single bar of Fels Naptha or Kirks Castile soap and mixing it with large amounts of washing soda and/or borax and/or baking soda. Often only 1 or 2 tablespoons (TBL) of this dry mix are supposed to be used per load, sometimes even less. Liquid laundry soap mixes and laundry soap "butters" can be more extreme -- sometimes a single bar of soap is used to make gallons of the mix.
A laundry mix with a lot of fillers and very little soap might be fine for lightly soiled clothes, but it will not efficiently remove accumulated body oil, food and other stains, or greasy soil. I want more from my laundry soap, so here are my conclusions after doing some research and practical experiments --
Borax and washing soda function in similar ways. Each of these ingredients helps soap clean better by maintaining an alkaline pH in the wash water and softening the water by chemically reacting with "hard water" minerals. Only one or the other is needed in a laundry soap mix, but which one you use depends on the type of laundry mix you are making.
Washing soda is best in a DRY laundry mix. It is more efficient than borax for maintaining alkaline pH and softening water as long as the washing soda stays DRY until the point of use. Washing soda degrades over time in a water-based product when also exposed to carbon dioxide in air.
Borax is best in a LIQUID laundry mix. It is not as powerful as fresh washing soda, but borax will remain stable and useful over time when dissolved in a water-based product. If you want to use washing soda with a liquid laundry mix, add dry washing soda separately to each wash load.
Baking soda is much weaker than washing soda or borax. It is not as effective at creating an alkaline pH or softening the water. Stick with washing soda or borax in a laundry soap mix and ditch the baking soda entirely.
Use plenty of soap in proportion to the other ingredients in a laundry mix. A laundry soap mix is supposed to clean, and soap is the ingredient that is doing the cleaning, so be sure there's enough soap in the mix to do the job.
Use enough laundry soap mix and the best water temperature to get the most effective cleaning. If you need to routinely pretreat even minor greasy spots and other stains or your dirty chore jeans are staying dirty despite a good wash, you may need to use more mix per load and/or use warmer water when washing these clothes.
Consider the hardness of your water. If you are washing in especially hard water, the washing soda or borax in your laundry mix may not remove enough of the hard-water minerals. The soap will react with these hard water minerals to create a gray soap scum that can make your whites turn dingy and make line-dried clothes stiff and scratchy.
The ideal solution for hard water is to install a whole house water softener. If that is not an option, try using more laundry soap mix per load and/or adding a separate water softener product. If these tactics do not work, you may have to go back to commercial synthetic detergents, because syndets do not form soap scum in hard water like a lye-based soap does.
Equipment needed to make laundry soap mix
A food processor is the best way to shred the soap and break it down into a fine powder. Shredded soap is too coarse to dissolve quickly in the washing machine. Some people get around this by soaking grated soap in water right before use and adding this liquid mixture to the washing machine. That's too much messing around for me! I use the food processor to turn the shredded soap into a fine powder that dissolves fast in the washing machine tub.
If I could not powder my dry soap finely enough to use directly in my washing machine, I would make a true liquid soap from coconut oil and potassium hydroxide (KOH) and add this soap along with dry washing soda to each load of laundry. But liquid laundry soap is not the focus of this article.
Safety equipment is also important. The soap and other ingredients in a laundry mix are irritating to the skin, so wear gloves. Washing soda and other powdered materials are also dusty and irritating to the lungs, nose, and eyes. If you have a stove hood that vents outdoors, work under the running hood if you can. Another alternative is to work outdoors in a protected location.
Making the soap
My last batch of soap for the laundry was made with 70% coconut oil and 30% lard, but a soap with 100% coconut oil is an even better choice. Coconut oil soap is a strong cleanser, which is not so good for our skin but is great for clothes. It also dissolves easily, even in cold water.
I use zero superfat and a 30% to 33% lye concentration. At trace, I pour the soap batter into a simple loaf or slab mold and set it in a safe place to finish saponifying. Coconut oil soap saponifies quickly, and it will probably get hot enough to gel (and even crack) without insulation.
If you have hard water, you may want to consider adding a chelator such as tetrasodium EDTA or sodium citrate to your soap recipe. This will help reduce soap scum. Less soap scum means your soap will clean better, whites will stay whiter, and clothes dried outdoors on a laundry line will feel softer.
Shredding the soap
A soap high in coconut oil should be firm enough to unmold 12-18 hours after it was poured into the mold. That is usually the best time to shred the soap. The soap may still be warm to the touch and perhaps a bit zappy (slightly lye heavy) at that point, but I wear gloves and work with it anyway.
Do NOT let the soap fully cure before processing it into a powder! My goal is to shred and powder my soap when it is firm but still has a pliable and waxy texture, like cheddar cheese. In my experience, that happens anywhere from 12 to 24 hours after pouring the soap into the mold. Experience is your best guide.
I weigh the soap log and record that weight for later use. It is easier and tidier to weigh the soap log than to weigh the shreds afterwards.
I roughly cut the soap log into large chunks that will fit into my food processor chute and grate the soap with the shredding blade in my food processor. You can also use a hand grater or salad shooter.
Sometimes when I start grating, the soap will smear around rather than form clean shreds. If this happens, the soap is still too damp to work with. I let the chunks dry for a few hours to a day and try again.
I spread the batches of shredded soap into large flat pans to cool and continue to dry while I work on the rest of the soap. If the shreds are piled high in a bowl, the shreds in the middle will stay warm and damp enough to stick together. The shreds need to be loose and fluffy.
My original recipe for a dry mixture is about equal parts by weight of soap and washing soda. Shredded soap varies too much for a volume measurement to be accurate, so measure by weight for best results.
I have been experimenting with including an oxygen-bleach powder in the laundry soap mix, rather than adding it separately to each load of wash. My latest recipe uses equal weights of oxy bleach, soap, and washing soda. If I'm adding oxy bleach to the mix, I would also weight it out at this point.
Oxygen-bleach powder reacts with water, so oxygen bleach may become less potent if blended into a dry laundry soap mix. That might seem odd at first glance -- after all isn't a dry soap mix, well, dry? Yes, but the soap itself still contains a small amount of water even though the overall mix is dry to the touch. For this reason, the oxygen bleach may be more potent if added separately to each wash load.
Making the mix
Now it's time to make the powdered mix. I change to the blade in the food processor and fill the bowl about half full. Do not over-fill the bowl for most efficient processing. Use about 1/2 soap shreds and 1/2 washing soda and/or oxy bleach. I process the soap mix until the shreds break down into a fine powder. It takes about 30 seconds per batch.
If the soap starts to form larger particles or even ball up in the processor bowl, that means the soap is getting too hot and soft so it is smearing together. The solution is to stop, add a big handful of washing soda or oxy bleach, and try again. If the soap still balls up even after adding more powder, spread it out in a pan to cool and dry some more and try again a few hours to a day later. The powdered soap should be about the size of kosher salt or coarsely ground pepper, so it dissolves fast.
I put the finished powdered mix back into the flat pans to cool and dry. If the soap is not quite fine enough, I may put the mixture back through the food processor to see if it will break down a bit more.
If there is any washing soda or oxy bleach left over when the soap is all processed, I blend the leftovers into the cooled soap powder and then package the finished mix in a large tub for storage.
Using the mix
I use 2 to 4 TBL of the basic soap and washing soda mix per load. I have an HE (high efficiency) washer, my water is soft, and this works pretty well.
If I have included the oxygen bleach powder into the mix, I increase the amount of powder used per load to account for the added oxy bleach.
A lot of people want their soap mix to have enough fragrance to scent their clothes after they are dry. I think a whiff of fragrance makes doing the wash a wee bit more pleasant, but I do not expect nor want much scent to linger in my clothing. Just my preference.
I have added an FO (fragrance oil) or EOs (essential oils) when making the base soap -- exactly like I would scent a regular bath soap. The resulting laundry mix has a nice fragrance, but the scent dissipates and does not scent the clothes.
I have tried adding scent to the food processor while powdering the soap, but the smell around the food processor was overwhelmingly strong, so this is not a particularly good nor safe method. The scent does not linger in the clothes.
Another person shared that he puts 10-15 drops of fragrance directly in the soap dispenser of his washing machine. He says that does leave a scent in the clothes, so this tip might be worth trying if you prefer scented clothing.
I figured the cost to make a batch of my laundry soap mix. My cost included the cost of ingredients plus paying myself the same hourly wage I pay to the ladies who help me in my business. I prefer Tide when I use commercial laundry detergent, so I compared the cost of my mix to Tide products.
Bear in mind that scent is expensive, and this extra cost can really drive up the per-load cost of your laundry soap mix. I did not include the cost of fragrance in my calculations.
My first comparison was my laundry mix with oxy bleach versus Tide with Bleach Alternative. The Tide product costs $18 and will do 72 loads, as stated on the label. Cost per load comes to $0.20 for my mix and $0.25 for Tide. Modest savings.
I then omitted the oxy bleach and compared my basic soap mix to plain Tide which costs $18 and will do 96 loads. The cost for the mix drops to $0.10 per load vs $0.19 for Tide. Definitely cost effective.
There are a couple of issues that make my laundry mix even more cost effective. It is very easy to over measure the amount of Tide per load if I use the cup that comes with this product. I doubt I ever got the full number of loads claimed on the label. I also did not like how my washing machine (top loader HE model) got stinky when I was using Tide regularly. When you factor in the cost of overuse and the cost of that pricey washing machine cleaner stuff, the per load price of Tide goes up.