Horse Chestnut and Buckeye Laundry Soap

With social distancing rules keeping us at home we’ve had the opportunity to thoroughly explore our place and boy, have we been discovering interesting things. One day my kids came back from a walk and said they’d found a chestnut tree by our landlord’s shed. I thought “wonderful, another source of food to forage!” and went to collect some. I noticed they were a bit different to my mother in law’s chestnuts and I vaguely knew of poisonous horse chestnuts so I did some research which confirmed the kids had found horse chestnuts, Aesculus hippocastanum, also known as conkers.

Distinguishing Horse Chestnuts and Buckeye from Edible Chestnuts

The clearest differences are that edible chestnuts have a little tail on the nut that horse chestnuts don’t, and the seed casing of a horse chestnut is less spiky. See my photos below.

Now to make matters more interesting, just prior to my kids’ discovery I noticed another chestnut look-a-like in our yard and with some help from plant lovers on Facebook I was able to identify it as Buckeye, another Aesculum species. It looks like this:

Even though horse chestnuts and buckeyes look similar to edible chestnuts, they’re not related. Edible chestnuts are from the genus Castanea, not Aesculum. In fact, they are not even in the same plant family, with Castanea belonging to the Fagaceae family and Aesculum belonging to the Sapindaceae family. Sapindaceae is the same family that soap nuts, a natural laundry agent, come from. Horse chestnuts and buckeye also contain saponins, a soap-like chemical compound which is a surfactant (sapo is Latin for soap), but edible chestnuts do not. Saponins are mildly toxic and that is the reason horse chestnuts and buckeye are not edible in their raw state.

Making Laundry Soap from Horse Chestnuts and Buckeye nuts

All this plant identification work led me to find heaps of articles about making laundry soap from horse chestnuts, but actually none involving buckeye. Maybe that is because many people apparently mistakenly interchange the names buckeye and horse chestnut. Anyway, I decided to try using both to make my own laundry wash, because how awesome would it be to be self sufficient in soap! What a reduction in my family’s ecological footprint; not only is it homemade soap, it’s homemade soap without any travel miles attached to any ingredients.

You don’t have to be too precise about this, so begin with a handful of nuts, I think I had about 7 or 8. Chop them up with a knife or use a hammer to break them open.

I shelled mine because it wasn’t too hard to do and I couldn’t see the benefit of keeping them, but maybe I’m wrong and the cases also contain saponins. I couldn’t find an answer to that. I read that some people on the web don’t include the cases because of concerns about staining light coloured clothing, however others who keep them say they haven’t noticed any staining.

I continued chopping the nuts into small pieces but some people use a blender to make it very fine. The smaller the pieces, the quicker the nuts release the saponins.

Next poor boiling water over the nut pieces and stir. Leave to steep for anywhere between 30mins and overnight.

Finally strain the liquid and use that as your washing soap. I don’t know how much water I added to begin with but I had almost 300ml of liquid soap once strained.

I used all of this for an 8kg load of washing that included soiled garden and work clothing. I only do cold water washes.

The clothing came out completely unscented (you could add some essential oil to the liquid if you like) and most things were clean. As I expected it didn’t remove stains and there was a couple of items like the jumper in the photo that still had some stuff on it. Overall though it wasn’t a bad result for the horse chestnut laundry liquid or the buckeye laundry liquid. I’m encouraged to keep trialling their uses.

Storage

The liquid laundry wash can only be kept for up to a week in the fridge, after that it will spoil. However, you could preserve the nuts by drying them after you have chopped them into small pieces; just add boiling water to a cup full when you are ready to use. This would allow you to prepare a large supply while the nuts are in season. I’ve done this but the nuts do need more time to steep after they’ve been dried to release the saponins.

Other Thoughts and Further Investigation

Given this is a mild natural surfactant, I thought it would make a great wool wash. I tried it out with a couple of drops of eucalyptus oil to hand wash my large cardigan. There were no problems and my hands felt super clean when I finished.

I’m wondering why no one is using this liquid ‘soap’ as a hand wash or dish wash? From what I can establish the liquid soap is just like other soaps. It’s fine to wash your body and dishes with but you wouldn’t eat it. I’d love to know if anyone can shed more light on the toxicity of horse chestnuts and buckeyes.

I’m thinking this might be an excellent biodegradable washing soap for camping situations but my reading revealed that the saponins are toxic to fish and in fact were used by Native Americans to stun or kill fish, so the rule of not emptying your washing water into or near streams while camping still applies. Just because it is natural and biodegradable doesn’t mean it is harmless.

I’m aware that a Choice review found that soap nuts were only as good as using ‘just water’, so time and experimentation will tell how well these continue to wash for me.

I wonder if the toxicity level would have any long term impact on my septic tank system or compost? I think it is unlikely but worth considering given there is some hype on the internet about the toxicity of horse chestnuts and buckeyes.

Please feel free to share your thoughts, experiences and knowledge. I’d love to hear from you.