Could it be that similarly a few very large international companies are controlling the world's soap supply? For the sake of this Instructable the presupposition is that indeed it is needed to reduce dependency on Big Soap, thus using less natural resources and reducing expenses (and Big Soap's profit) in the process.
In everyday use it is quite common to use the amount of liquid handwash supplied by a full single stroke of the dispenser's handle. And who determines the amount supplied? Yes indeed, the designers of Big Soap!
This Instructable presents four approaches for reducing the use of liquid handwash. These approaches are all improvements with regard to the liquid soap dispenser using a hand-powered pump and can be considered as Green Design because they advocate concepts for a more sustainable use of resources:
1. Engineer's Approach: reduce the stroke of a soap pump piston (Step 2)
2. Salesman's Approach: dilute the dispenser's soap with water (Step 3)
3. Approach of Self-Control: don't push it too far (Step 4)
4. Environmentalist's Approach: use tablets of soap instead of liquid handwash (Step 5)
In order to give some background to handwashing Step 1 recaps some theory. Additionally, the amount of soap that is being dispensed in a full stroke of an average soap dispenser is being estimated and consequently the price of a single handwash is being determined.
Step 1: Liquid Handwash: Theory and Statistics
Let's now try to quantify the amount of soap that is being supplied at a single stroke of the handle from a small sample (n=4) of soap dispensers.
The soap dispensers were purchased in a regular shop, ranging in price from EUR 1.82 to EUR 2.56 (US$ 1.40 to US$ 1.97). In terms of specific costs, the four samples range from EUR 6.07 to 10.24 per liter (US$ 0.08 to 0.13 per cu in).
The amount of soap being dispensed at a single stroke of the hand-pump has been determined by counting the number of cycles required for pumping a total volume of 50 ml (3.05 cu in). This resulted in a range of 25 to 50 cycles.
The resulting soap volume dispensed in a single stroke can thus be determined at 1 to 2 ml (0.06 to 0.12 cu in per stroke).
Consequently, the price of a single handwash is 0.7 to 1.9 eurocent (US$ 0.006 to 0.015). This calculation does not take into account the costs for the water that is needed in the process and assumes that the quality of the soap is not a factor influencing the required quantity.
The chart's trendline does not really provide any particular insight to the correlation between 'supply volume per stroke' and 'specific costs' (R-square is very small). Readers of this Instructable are invited to populate the database with own observations. To do so, the Opendocument Spreadsheet (.ods) is available on request. Data communicated through a PM might be integrated and released in an update for this instructable.
The latter derived parameter, the specific costs, is most relevant but cannot be influenced by the user after having purchasing the dispenser. The first parameter however, the supply volume per stroke, can be influenced by the user.
The next steps document approaches for reducing the amount of soap being dispensed and thus lowering the expenses of a single handwash (assuming that the quality of the washing process remains unchanged).
Step 2: Engineer's Approach: Reduce the Stroke of a Soap Pump Piston
Whether or not this mod can be successfully applied highly depends on the design of the dispenser's handle. In case there is a ring that sinks into a cylindrical cavity this hole can be stuffed with a solid material. The pictures show how flexible tubing (blue) can be used as a bumper, thus reducing the stroke of the piston and consequently reducing the soap supply per touch. The height of the bumper is a measure for the supply reduction. Note that this modification is completely reversible.
First measure the depth of the cavity and then determine the supply reduction you'd like to achieve. In this Instructable the depth is 10 mm (0.4 in) and the bumper was cut at approximately 5 mm (0.2 in) to achieve a 50% reduction. This worked out fine. Note that users might notice that the stroke is less than it has been before. Therefore, do not cut down the dispenser's stroke too much in order not to annoy the other users.
Flexible tubing as such comes in handy for lots of products and modifications. Among others it was a nice basic material for designing the openproducts' earlier released 'Easy Cable Clip'.
If your soap dispenser is not suitable for the Engineering Approach then you could try to purchase a better suited soap dispenser at your next visit to the shops. Else, there are three different approaches left to be discovered in this Instructable. The next step documents the Salesman's approach.
Step 3: Salesman's Approach: Dilute the Dispenser's Soap With Water
In this Instructable a dilution of 50% was carried out. Users will most probably recognize the change in viscosity, as the result is a very watery liquid soap. In the experiment for this Instructable it was first tried to mix the water and the liquid soap very gently. The result however was quite some lather, which disappeared after some hours. After 48 hours however the soap seemed to precipitate on the bottom of the dispenser. Apparently adding water to liquid soap ruins its properties. The challenge here is to modify the diluted liquid handwash in such a way that its original viscosity is not affected too much (I have no suggestions to realize this, feel free to comment). Until then, key to the Salesman Approach might be to use a dispenser that is opaque instead of transparent (which has been chosen for being able to follow the experiment closely).
* If you're interested in energy saving by reducing the stand-by energy use of a combi boiler you might find relevant information in this openproducts' Instructable. If you're using a single-handle mixer tap be aware about its functioning, and the possibility of unintentional use of hot water, resulting in an increased energy bill. See the One-Armed Bandit - Mixer Tap Redesign.
If you don't feel comfortable about diluting your liquid handwash (me neither) then the next Step, which is actually the most easy and most flexible of the four approaches, you might like better: simply don't push the handle of your handwash dispenser too far.
Step 4: Approach of Self-Control: Don't Push It Too Far
The next step documents the most sustainable approach in this Instructable, namely to refrain from the plastic bottle and the water.
Step 5: Environmentalist's Approach: Use Tablets of Soap
There is another reason why not to use liquid handwash, or at least to pay attention to its ingredients: in the recent past Big Soap (during the last 10 to 15 years, I've read) has been adding microplastics to products for personal care (shampoo, toothpaste, creams, etc.), which after usage travel via the sewer system (I read that not all microplastics are being removed in sewage water treatment) and rivers to the oceans, to possibly end up in the food chain.
If you'd like to have clean hands then a safe choice is to opt for natural products, which refrain from chemical additives. Products with an Ecocert label for example guarantee the absence of GMO, parabens, phenoxyethanol, nanoparticles, silicon, PEG, synthetic perfumes and dyes and animal-derived ingredients.
The next Step discusses the design features of the Engineering Approach and the last step highlights the CC BY License under which this Instructable has been released.
Step 6: Design Features
The next step elaborates on the license type chosen for this Instructable.
Step 7: License
Republishing this Instructable is allowed, provided it is being attributed properly (cite the name openproducts, link to www.openproducts.org, www.instructables.com/member/openproducts, or the original Instructable. For other arrangements send a Private Message through the instructables member page (www.instructables.com/member/openproducts).
If this design infringes any rights then refer to Article 28 in the Terms of Service (www.instructables.com/tos.html).