Shampoo Residual Losses

When a consumer is finished with a product, it’s rare that the product is truly empty. The product remaining in the container at the end of life is called ‘residual product’ and essentially amounts to a waste for both the consumer, and the environment. A 5% residual loss represents 5% more product you will need to buy and manufacturers will need to create. Aggregated across a whole market segment, this loss is enormous. Failing to find adequate public research on the subject of residual loss rates, we conducted a micro-study to answer the question:

How much shampoo is left in a bottle when a consumer considers it empty?

Methodology

To get the 6 bottles (5 shampoo and 1 facial cleanser) my cofounder and I waited until the bottles in our homes were ‘finished’. We left this element intentionally vague, although we said no rinsing or cleaning the bottles out was allowed. We wanted to use shampoo bottles that were perceived to be empty.

We then weighed the bottles we had to get the total weight at the moment of potential disposal or recycling.

We then gave the bottles a thorough rinse to clean out any left over product and dried the bottles.

Finally we weighed the bottles and the closure systems, and subtracted our initial weight from the final weight to arrive at the Loss Mass and Loss %.

Loss Mass is measured in grams, while the loss rate % is equal to the loss mass divided by the total ingredient mass.

Total ingredient mass (of a new, unopened product) was estimated by multiplying the volume by a density factor of 1.04, which is recommended in the European Commission's PEFCR guide for shampoos.

Results

This view shows the volume and container type.

This view shows the materials in the containers.

Discussion

Losses range from a low of 1.9% ingredient mass loss to a high of 8.4%.

Potential factors involved in the loss rate:

Viscosity of Product

The more viscous the product is, the harder it is to flow from the packaging container. The product with the lowest loss rate was a Facial Cleanser, which typically has a lower viscosity than shampoos.

Container & Closure Shape/Design

The highest loss rate was for the Laboratories Klorane bottle, which deviated from the normal rounded edge design of the other bottles. It had sharp corners, and the closure system sat atop the straight edge of the bottle. Contrast to the Garnier shampoo bottle, where the edges are rounded and feed into the closure system at a less sharp angle.

Container Material

Polyethylene Terephthalate (PET) bottles may present a tougher ‘squeeze’ than High Density Polyethylene (HDPE) bottles. Loss rates may be linked to the 'squeezability' of the bottle, which is likely linked to the material.

The highest loss rate came from this bottle and closure configuration.

The second lowest loss rate came from this bottle.

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Just a man and his bottles…

Future analysis will focus on primarily having a larger sample size, and taking into account the above factors more stringently in data collection; such as viscosity of product and some metric of 'squeezability'.

Eager to get started collecting some more bottles and learning more about this particular issue!