Spar-Klean Science: Home-Made Washing Up Liquid


I’ve tried lots of recipes over the past few months and none have worked from an aesthetic point of view.  Sure they all cleaned, they all smelt gorgeous and very lacking in chemicals and they were all kind to sensitive hands.  Thing was, they were scummy.  Or at least they left a nasty scummy water behind, which made wonder what exactly would be left on my dishes.

It was only when I looked into the chemistry of the substances I was using that I understood what was going on and why I had this nasty scum all the time.

The Chemistry of Washing Up Liquid

Pull up any recipe and you are likely to find grated soap, possibly liquid soap (sometimes both), washing soda, vinegar, glycerine and essential oils.

Here’s a run down of what they do:

Grated soap/castile soap

Used for cleaning.  They work because they have both hydrophobic (non polar and therefore water repelling) and hydrophilic (polar and therefore water-soluble) properties.  This means they act as emulsifiers, allowing the water and oil (for example) on the dishes to mix and therefore be removed into the water.

Washing soda

Washing soda (Na2CO3 ) is a carbonate which is traditionally used in detergent to treat hard water by binding to the minerals that make the water hard and preventing scum, allowing good lathering of soap to occur.  Washing soda also has a thickening effect on the washing up liquid.


A humectant, it increases moisturizing properties of any soap based product


An acid, it is traditionally used to soften water and is an excellent rinse aid.  It is also antimicrobial

These were all the ingredients I had tried, bar the castile soap (it is hard to get and fairly expensive in the uk) and the results were a little revolting to be honest, in terms of scum.  I knew we were in an area of extremely hard water, to which my kettle regularly testifies.  I thought that would have been sorted by the vinegar.  Of course when you look at each individual chemical used you realise fairly quickly that using a strong alkaline (washing soda) and mixing it with a strong acid (vinegar) would immediately negate the effect of both by causing a neutral solution to be formed.  This meant the water hardness remained much the same, hence the scum.  So I got rid of the vinegar as I felt the properties of the washing soda were more important than the vinegar (the washing soda would act as a water softener and if I chose my essential oils well I knew I could replicate the antimicrobial properties of the vinegar, therefore deeming it superfluous to my recipe).  So back I went and tried again.  But alas had the same problem.

The recipes all call for grated soap to be dissolved in hot water and I surmised that it was at this stage that the soap was reacting with the hard water and causing scum, which transferred itself to the dishwater when I was washing up.  To be honest, I’m not sure if I’m right in that assumption, but the resulting changes I made based on this thought worked.  I had seen some pure liquid soap in the laundry aisle at Waitrose, which was literally just soap and water beautifully mixed together without any sign of scum.  At £3 it was a bit steep, but my plan was to mix it with other ingredients including water to bulk it out a little.  Anyway, I couldn’t help but try, just to satisfy my own curiosity if it would work or not:

Dri Pac brand of Liquid soap flakes and soda crystals, with Tea Tree oil
Dri Pac brand of Liquid soap flakes and soda crystals, with Tea Tree oil

And it worked a dream.  Really.  It was pretty much exactly like using Ecover, the brand I would usually use.  And it worked out slightly less expensive, took seconds to make and T12 was so impressed that he chose it over our normal brand.  C11, though, had to wash up some very greasy dishes which had had lamb mince in, and she did not find it as good.  So I think probably it is perfectly adequate unless the dishes are very, very greasy and then maybe a shop bought brand is better (we eat lamb so infrequently that the home-made brand is just fine for us)

Here’s the basic recipe below.  Can I offer a word of advice?  Not all water is the same (hard or soft) and not all washing soda is the same (home-made tends to be weaker than bought; super is stronger than basic).  If you try this recipe and find it isn’t quite right, play about a bit.  I did, and it really is perfect now.

Claire's home made washing up liquid!
Claire’s home-made washing up liquid!

Angelicscalliwags Washing Up Liquid

  • 1 cup pure liquid soap flakes (I use Dri Pac)
  • 2 cups boiling water
  • Heaped tablespoon washing soda
  • Approx. 10 drops essential oil (I used tea tree oil)
  • If it dries out your hands feel free to add some glycerine (or wear gloves)

Dissolve washing soda in boiling water, add to liquid soap, cool and add essential oils.  If once it is cooled completely it seems a little runny, next time try slightly more washing soda.  Mine is the consistency of normal shop bought Ecover.

Easy peasy, just how I like it:

I'm not sure if this shows you what it looks like or not.  It is fairly thick, translucent liquid, which smells however you want it to and suds up really well.
I’m not sure if this shows you what it looks like or not. It is fairly thick, translucent liquid, which smells however you want it to and suds up well.

It makes just under 750ml for about £1 excluding the essential oils.  Without the essential oils this would come in 13p per ml, whereas Ecover sells for 30p per ml and Waitrose essential washing up liquid costs 17p per ml.  Without scent or antimicrobial benefits it is definitely cheaper homemade.  Obviously, depending on the oil(s) you use, it may well be less expensive to buy it in the shops.  I use Tea Tree oil because of its strong antimicrobial properties  and because I love the clean smell of it.  Also it is one of the least expensive oils to buy in the UK, keeping the cost of washing the dishes as low as possible!

I’m working on a general kitchen spray at the moment, one which would be safe for my littlest to use but also one powerful enough to keep our permanently in use kitchen clean.


  1. I love this post, Claire, the way you’ve explained what each ingredient does and why you’ve made your choices! I’m going to have to try your formula out! Thanks so much for sharing. I have very hard water here too so your formula is going to work out great for us.

    BTW, I used to use Ecover too. 🙂 All those chemicals in normal cleaning products are so harmful in the long run.

  2. I may have to try this. We make our own laundry soap, but have not yet tried to make dish or other soaps. Thanks for sharing!

    1. I’ve not found a laundry soap that works well for us yet. I gave up trying and thought I would concentrate on the kitchen chemicals rather than laundry. Our hard water gets in the way of many of the recipes I’ve seen online.

  3. For long periods of time we used vinegar for our general kitchen spray, until I figured out it was reacting negatively to our counters. Now, I’m back to the generic store bought one, but I’m still toying with making my own.

    I’m super impressed at your perseverance with this. I don’t think we have the same brands here in the US though.

    1. What kitchen tops do you have. We have oak (real not laminate) and I was going to start with a vinegar based spray. I absolutely don’t want to ruin my lovely oak so I think I’ll maybe stay clear. Mmm. I’ll have to do a bit of research here!

  4. I’ve never experimented with home made cleaning products but I read every line of this with fascination. I remember at school being really interested in the chemistry of soap. Definitely bookmarking to do with the kids at some point. Thank you!

    1. I enjoyed it much more once I understood the chemistry, because it wasn’t guessing anymore or so hit and miss. Instead I understood, vaguely, the whys of it all which definitely resulted in a better product!

  5. Good for you for working so hard to make this work for you. I use a product called Ecos which is coconut based with a lavender oil. We love it and it is friendly on the pocket book. When I get the urge, I make my own laundry detergent, but usually get tired of doing it and end up buying it.
    You have a greater understanding of the chemistry behind the products than me.

    Thanks for sharing.

  6. I never thought of adding washing soda – I’ve tried a few versions but they never came out quite right. Thanks for the recipe – I’ll be whipping some up today!
    Thank you also for sharing at the Natural Living Link-Up – Pinned and shared. Hope to see you there again next week!

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