Preserving our Plastic Shoes

When we think about modern footwear we may picture a pair of trainers, chunky boots or those Balenciagas: the ones that look like socks. Whatever your preference, it’s likely that your shoes contain some plastics. Here the term ‘modern’ is used liberally to mean the 20th century onwards, but our journey really begins with the invention of vulcanised rubber in 1839. Charles Goodyear, the accidental father of vulcanisation, is still most associated with car tires – and funnily enough, most rubber shoes were produced by tire companies into the 1900s. New technologies were paired with a growing sports and leisure culture among working classes. As factory labourers flocked to the seaside during the summer, they exchanged their work boots for plimsolls, which were more resilient to sea and sand. These early rubber soles were made of natural latex but as demand increased and prices soared, many industries explored methods of synthesising rubber from oil. Inevitably, synthetic materials entered the clothing industry.

Plastic is durable, light, elastic and cheaply mass produced, meaning that it became very popular in decades to come. This also means more plastic in museum collections, transforming not only what is being collected but how these collections are being preserved.

In our ongoing project, ‘Lesser Known Voices: Curating Shoes in the Store’, we aim to improve the accessibility of shoes at Leeds Discovery Centre. Display trays will be based around select themes, ranging from 18th century slippers to 21st century sportswear and beyond. With over 600 shoes in boxes, we hope to showcase our collections and unbox some hidden histories in the process.

When we started this project, one thing we didn’t anticipate being an immediate concern was plastic. Working with textiles has its own conservation concerns of course – moths, light exposure and the inevitable weathers of time and wear being just a few. While we might think of centuries-old silks as our most vulnerable textiles, it was shoes from the 1970s that appeared to be in the worst condition. Think more Boogie Nights than Amadeus.

A pair of ladies slingback shoes from 1960-1979, ‘made in Italy expressly for Debenhams’. At the time the photo was taken the shoes appear in excellent condition.

20th century platforms was the theme, but upon opening the first box – a brightly coloured pair of slingbacks – there were noticeable cracks on the heel and mould along the platform sole. By the second box we had higher expectations, which opened to reveal well-preserved green leather shining back.

In the summer of ’74 these platform sandals were bought in a sale for £3 (approximately £29 in today’s money) on Leeds Briggate. Based on the price, they can be considered accessible high-street fashion, with soles made from imitation bamboo and uppers made of leather. Since they were donated in 1993, the leather has not discoloured, and the beige embossed pattern is still easily visible.

Green platform sole sandal with slingback from 1974. At the time of this photo, there was already some cracking through the sole.

However, as one shoe was lifted, what remained at the bottom of the box was a sad reminder of the importance of preventative conservation. What likely started as some cracking, had clearly got worse over time as the sole completely detached from the leather and eventually crumbled into pieces.

Photographed in November 2021, the sole of the shoe is now completely detached from the upper part. However, the leather shows no evidence of deterioration.

The big question for us was: why are two pairs of shoes from the 70s in such poor condition in comparison to those from hundreds of years ago?

The answer is that plastic has a short lifespan compared to traditional materials found in museums. The sheer amount of plastic in a platform sole makes them especially vulnerable to degradation, creating some issues for curators centring a display around them 50 years later. Condition reports written in 2008 and 2009 show some deterioration to the shoe but it appears no action was taken to slow this degradation down.

This raises another important question: What courses of action could have been taken to preserve the shoes?

Unfortunately, we can’t know for certain why conservation measures weren’t taken back in 2008. A clue might be found in the first pair of mouldy shoes which are still reported to be in good condition, suggesting that they had not been seen since noticeable deterioration began. From a scientific perspective, plastics have a long induction period followed by accelerating degradation. Basically, what looks in good shape one day may be a pile of dust six months later. By the time we can see (or smell) anything is wrong, an irreversible chemical reaction has already started, a process that can be slowed down by conservation but cannot be stopped.

In terms of mould however, things look a bit more optimistic. Freezing or air drying an object should kill the mould spores followed by storage in a dry, temperature-controlled environment.

Photographed in November 2021, the shoe now appears to be mouldy, both on the sole and the upper. There is also some cracking in the heel.

In cases where nothing can be done, the second option is disposal.

Disposal generally means that an object is transferred from a museum’s collection, often freely to another public institution that can provide suitable care and access. This is a core part of responsible and sustainable collections management. It is about weighing up our ability to protect these shoes for future generations against the potential loss of an historically important object from our collection. One justifiable reason for disposal is that an item is damaged or deteriorated beyond the museum’s ability to repair. If the sandals are determined to be beyond repair, this limits the possibility of transferring to another institution. In which case, the item may be returned to their donor or recycled.

A piece of the platform sole, made from plastic to replicate bamboo sticks. The plastic is crumbly and sticky.

Ultimately, we will not be able to display our two most visually striking ‘70s platforms in the trays, forcing us to rethink the theme entirely. In this way, condition issues have already impacted the direction of the project, issues which may reoccur as we focus more on 20th century shoes.

On the upside, the project has proven to be a great way to check the condition of the collections, some of which have remained untouched in their boxes for years. What this setback did stress was the importance of regular condition checks for preventative conservation purposes. Discovering the first pair of platforms early potentially extended their lifespan significantly. Raising awareness of conservation issues through our shoes is a crucial step in tackling the deterioration of plastics of any type within museums.

By Bethany Lunn, ‘Lesser Known Voices: Curating Shoes in the Store’ Project Placement