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A little shampoo bar experiment.

June 13, 2018

There’s been a bit of a buzz on Facebook this week about solid shampoo / shampoo bars this week so I thought I’d delve a little deeper, the net result of which was the production of these rather crude but also quite cute shampoo snow balls – don’t you just love it when a plan (or a shampoo ball) comes together…

Anyway, the appetite for all things packaging free (especially plastic free) is growing and as such, shampoo bars fit right in. They are super concentrated,  super easy to travel with (light and non leaking although they might get crushed I guess) and super efficient offering a more concentrated clean than your average shampoo.

I took a look on the market to see what was already out there and found two distinct types of formulation – the saponified bar and the detergent bar.

Lush dominates the synthetic detergent type of product with their good-old-fashioned Sodium Lauryl Sulfate needle formulation. I have always admired Lush’s ability to get away with selling what the internet deem as ‘nasties’ without it seeming so, maybe the fact that these shampoo bars were ultra-appealing to the ‘green’ market led to people overlooking their google-search chemical faux pas?  It sure looks like it. In any case Lush basically cake together the SLS needles with a few other bits of glitz and glam and voila, a shampoo bar is formed and it soaps up like a trooper.

In the non-synthetic detergent camp are bars of soap.  Now I’ve blogged before about washing your hair with soap and declared myself to not be a fan but I have to say that might have been a bit harsh in terms of an opinion, it’s just that my dad used to wash his hair in Imperial Leather soap and every time I tried it I ended up with a sludgy pile of dry, knotted hair for my efforts (we were a hard water, soap scum area).   Saponification kings and queens seem to have perfected the art of making a soap bar that isn’t all drying and scummy and as such have developed quite a following.  In fact there is a Facebook group devoted to the art of shampoo bar soap making and it has close to 3000 followers to date – impressive!

In terms of the natural-or-not stakes, both types can contain only naturally derived chemistry and can end up with similar environmental profiles on a weight/use basis which means there is no massive difference environmental impact wise on which one you choose but there are differences in terms of residual pH (pH when wetted.  Synthetic detergent bar soaps (which can be naturally derived) tend to have a residual pH of around 5-7 while saponified soap bars have a pH of 9-11 depending their super-fat level.  This may not be an issue but it definitely is a significant difference and could be a factor in the irritation or sting factor of the bar (although we’d also have to take the irritation potential of the surfactants into account too as that can be pH independent.

So if people are flocking to these bars to soothe their eco-soul are they right or are they mis-guided?  A bit of both it appears…

According to quite a few data analysts that I’ve read over the years the biggest environmental impact from your shampoo is the water used while using it – the time spent in the shower.  Apparently the ‘stuff’ that goes into the formula, the packaging and manufacturing only account for between 5-20% of the total impact with the in-shower water accounting for at least 80% of the carbon footprint.  This would be assuming that the water is heated using fossil fuel power and pumped to the shower using electricity which is also fossil fuel.  I expect that if the water was rain water, pumped and heated using solar or other renewable energy the impact would be different.

Out of the formula and the packaging we know we can’t do away with the formula but we absolutely can go packaging free (naked) as long as we can master a solid bar so let’s look at that.

Packaging of regular mass-market shampoos is mainly plastic based and most, though not all are recyclable but not infinitely so.  Also most will struggle to biodegrade at the end of their lifespan so we will still be left with a problem.  The trouble with shampoo formulations is that they typically contain a decent percentage of water – often between 40-80% – an ingredient that then adds to the shipping cost and volume while creating the need for plastic packaging due to the wetness of the formula.   Taking that out solves a couple of issues, if it is possible.

A typical ‘wet’ shampoo formula structure is something like this:

Not all surfactants are usable when 100% active, some are too slow to ‘wet’ or become foamy, others are too stripping -I’d almost say that SLS needles fit into here but clearly some people can tolerate them.  So when going for a solid formula we do restrict our surfactant choice.  Now the one thing that I’m a big advocate of is efficient formulating, there is no point creating a shampoo bar that is rubbish as that is the ultimate waste or time and resources.  So we still need our product to perform well.

Now our solid bar formulations don’t have to be water free, they just have to be able to come together as a solid.  I ended up making a bar that contained 28% water which is a lot less than a normal shampoo but it’s definitely some.  Having some water in the formula is often required to help the ‘bar’ form or bind together.  In my formula I’ve used the water to help me form  a gel between the emulsifier (a blend containing Sodium Stearoyl Lactylate, Cetearyl alcohol and glyceryl stearate) and Cetearyl alcohol.  These two ingredients form a non-oily, low-tangle-potential gel network in which the surfactants can nestle and solidify.  An alternative method would be to form a gel using a gum such as hydroxyethyl cellulose or xanthan or equivalent and then using that to house your surfactants. I chose not to do that as I wanted a more conditioning, gentle cleanse rather than the user feeling the full force of the surfactants.

So in my solid bar I’ve used Sodium Cocoyl Isethionate, the emulsifier (which has some anionic surfactancy) plus Sodium Stearate.  Sodium Stearate is a traditional ‘soap’ so I’ve paid homage to my soapy friends there but the other two are ‘synthetic’ naturally derived ingredients.   Sodium Cocoyl ISethionate is the original SYNDET soap bar ingredient and I chose that as it has a low water solubility compared to some surfactants so it won’t disappear immediately on wetting, it has a good foaming ability and a mild skin profile.  The only down side is that this isn’t the best for aquatic toxicity so I wouldn’t recommend using it as the only surfactant in a blend, especially if you wash a lot and your water goes out into a river rather than through a water treatment plant.   That said, this has an excellent biodegradation profile and is a good performer and is perfectly manageable when it goes through a treatment plant.  The Sodium Stearate (normal soap) is also a bit of an issue in aquatic environments although not quite as bad as our other friend.  The biggest issue with this soap is its biodegradation, as it degrades it gets a bit more toxic.  The Lactylate is very clean and other ingredients in the mix aren’t too bad to be honest.  The net result of my investigations here were that I ended up feeling a bit like ‘you solve one problem and create another’ – I was a big bummed that my solid shampoo was still likely to cause some negative impacts on the environment if used in large volumes – but after doing a few more calculations I realised that I was probably being over-utopian in my thinking and that as long as people were sensible the benefits would most likely still out-shine the risks.

So what does the finished formula look like?

This is what I ended up with and you can see how that looks at the start of this article.  It’s just a rough-and-ready formula to be honest, could be better, could be worse but in terms of performance it’s really very marketable.

I tested this out on my hair and found it lathered well and was pretty much bang-on for efficiency.  I had calculated that this shampoo bar contained around 65% surfactant which is around 3 times more than a regular shampoo.  I used 1.42g of product to wash my hair vs around 4.5g of regular shampoo which equates to a 1/3rd dose for the solid shampoo – so a pretty much equal surfactant exposure overall.  Now one wash does not a scientific experiment make but it was a good enough starting point for me to feel that this is something worth pursuing.

Environmentally the savings in terms of freight space and packaging materials are significant I feel.  Sure the product would need to be packed in something but with it only taking up 1/3rd of the space of a regular product there’s more than a little room to be creative without losing the benefits here.   Cost wise the price of my creation vs a regular shampoo seemed reasonable too.  Keeping in mind I’ve used small batch pricing and an expensive essential oil blend I got my in-use dose cost to be around the $0.045 mark vs my normal liquid shampoo which comes in at $0.098 (I buy this usually

Overall I’d have to say that I’m finally tempted to change my whole household over to shampoo bars and this formula looks like a good starting point for me.  I’d probably use some of my cost savings to swap some of the Sodium Cocoyl Isethionate out for something like Sodium Stearoyl Glutamate just to up the environmentally friendly ratings specially as the primary surfactant has to be used at a fairly high dose but other than that I’d not be inclined to change much at all.  I did use a powdered preservative in this but there would be no harm in using a liquid one, after all a wet paste is being formed. I’ve no idea at this stage if that preservative would even be able to preserve a product like this though, the water activity is very low (until the bar is wetted and left with hairs on to try in a soap bowl) so it could be fairly low-risk but I’d have to test it before ruling out the need for a preservative or finding it needs something stronger.

To sum up I’d say that even though your wet shampoo formula/ bottle/ transport/ manufacturing  only makes a relatively low contribution to your carbon footprint if you live in a coal or gas-fired electricity/ water heated home, it still makes some impact and let’s face it, those plastic bottles do soon stack up in the recycling bin if you’ve got a family living with you so why not experiment with something else!

A solid shampoo may not be able to be everything that your wet shampoo can be but it can certainly be innovative, relatively mild, environmentally friendly, ultra-portable and, if you add a bit of colour and a nice smell, a bit of fun to boot! I think I just converted myself.  Off to the lab I go…

Amanda x

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