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class="masthead-home-link" href="/global"> <img alt="The Conversation" src="https://cdn.theconversation.com/static/tc/@theconversation/ui/dist/esm/logos/logo-en-b159aca2598f351db37072c75294e4c8.svg" /> </a> <form class="masthead-search" action="/global/search" accept-charset="UTF-8" method="get"> <fieldset> <legend>Search</legend> <div class="row"> <div class="input-wrapper"> <label for="q"><i class="icon-search"></i></label> <input type="text" name="q" id="q" value="" placeholder="Search analysis, research, academics…" /> </div> <button type="submit" class="button" value="Search"></button> </div> </fieldset> </form> <div class="masthead-tagline"> Academic rigour, journalistic flair </div> </header> <nav id="primary-navigation" class=" nocontent"> <ol> </ol> </nav> </div> </section> <div id="outer"> <article id="article" class="clearfix has-desktop-magazine has-mobile-magazine" data-id="131712" itemscope itemtype="http://schema.org/Article"> <figure class="magazine"> <div class="image" style="background-image: url(https://images.theconversation.com/files/335985/original/file-20200519-152320-1azjfio.jpg?ixlib=rb-4.1.0&rect=0%2C0%2C3097%2C1546&q=45&auto=format&w=1356&h=668&fit=crop);"> <div class="placeholder-container" style="--aspect-ratio-percent:85.625%;--background-color:#48433a"><img class="lazyloaded" src="https://images.theconversation.com/files/335985/original/file-20200519-152320-1azjfio.jpg?ixlib=rb-4.1.0&q=20&auto=format&w=320&fit=clip&dpr=2&usm=12&cs=strip" data-id="335985" itemprop="image"></div> </div> <div class="wrapper"> <figcaption> Cellulose triacetate 16 mm film with severe vinegar syndrome, dated 1968. <span class="attribution"><span class="source">Ida Ahmad</span>, <span class="license">Author provided</span></span> </figcaption> </div> <div class="magazine-title"> <div class="wrapper"> <header class="content-header-container grid-twelve large-grid-eleven"> <div> <div class="content-header-block"> <h1 class="legacy entry-title instapaper_title" itemprop="headline"> <strong> Historical films may be decaying much faster than we thought thanks to ‘vinegar syndrome’ </strong> </h1> </div> </div> <div class="timestamps"> <time datetime="2020-05-19T07:30:24Z" itemprop="datePublished" content="2020-05-19T07:30:24Z">Published: May 19, 2020 8.30am BST</time> </div> </header> </div> </div> </figure> <div class="wrapper"> <div class="content-sidebar grid-four large-grid-four grid-last"> <section class="content-authors"> <div class="content-authors-synopsis"> <a href="#" class="content-authors-toggle"> <i class="icon-caret-down"></i> <i class="icon-caret-up"></i> <span class="nobr">Ida R. Ahmad</span>, <em class="institution_name">UCL</em> </a> </div> <div class="content-authors-group"> <h3 class="border">Author</h3> <ol> <li class="vcard" id="author-309842" itemprop="author" itemscope="" itemtype="http://schema.org/Person"> <a rel="author" itemprop="url" href="/profiles/ida-r-ahmad-943864"> <img alt="" class="lazyload" data-src="https://cdn.theconversation.com/avatars/943864/width170/image-20200518-83367-yx8ia.jpg" src="https://cdn.theconversation.com/static/tc/author/width170_default-bea415b3a0223821a698f6e3f6d5ab99.jpg" itemprop="image"> <span class="fn author-name" itemprop="name"> Ida R. Ahmad </span> </a> <p class="role"> PhD Candidate, Institute of Sustainable Heritage, UCL </p> </li> </ol> </div> </section> <section class="content-disclosure-statement"> <h3 class="border">Disclosure statement</h3> <p><span>Ida Rebecca Ahmad receives funding from the European Research Council under the European Union's Horizon 2020 research and innovation programme (grant agreement No 716390); and the Engineering and Physical Sciences Research Council (grant number EP/L016036/1). </span></p> </section> <section class="content-partners"> <h3 class="border">Partners</h3> <p class="disclosure-logo clearfix"><a class="logo" href="/institutions/ucl-1885"><picture><source srcset="https://images.theconversation.com/institutions/1885/logos/logo-1423469087.png?ixlib=rb-4.1.0&q=45&auto=format&w=170&h=170" media="(min-width:600px)"></source><img alt="University College London" src="data:image/gif;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs%3D" /></picture></a></p> <p class="funding-statement"><a 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data-href="https://theconversation.com/historical-films-may-be-decaying-much-faster-than-we-thought-thanks-to-vinegar-syndrome-131712" data-action="share/whatsapp/share" data-id="131712" target="_blank" rel="noopener" href="whatsapp://send?text=Historical+films+may+be+decaying+much+faster+than+we+thought+thanks+to+%E2%80%98vinegar+syndrome%E2%80%99+https%3A%2F%2Ftheconversation.com%2Fhistorical-films-may-be-decaying-much-faster-than-we-thought-thanks-to-vinegar-syndrome-131712%3Futm_source%3Dwhatsapp%26utm_medium%3Dbylinewhatsappbutton"><i class="icon-whatsapp"></i> <span>WhatsApp</span></a> </div> <div class="fb-messenger"> <a class="fb-messenger-button" data-href="https://theconversation.com/historical-films-may-be-decaying-much-faster-than-we-thought-thanks-to-vinegar-syndrome-131712" data-action="share/fb-messenger/share" data-id="131712" target="_blank" rel="noopener" href="fb-messenger://share?link=https%3A%2F%2Ftheconversation.com%2Fhistorical-films-may-be-decaying-much-faster-than-we-thought-thanks-to-vinegar-syndrome-131712%3Futm_source%3Dfb_messenger%26utm_medium%3Dbylinefb_messenger_button"><i class="icon-fb-messenger"></i> <span>Messenger</span></a> </div> </aside> </div> <div class="grid-ten large-grid-nine grid-last content-body content entry-content instapaper_body inline-promos" itemprop="articleBody"> <p>A significant chunk of the world’s history is facing an existential threat. <a href="https://www.wbez.org/shows/wbez-news/vinegar-syndrome-is-eating-away-cook-county-history/b7cb51f3-faee-4532-b710-3f9d5597fd90">US government deeds</a>, <a href="https://theconversation.com/cash-strapped-archive-struggles-to-preserve-indigenous-history-5015">recordings of Indigenous Australians</a> and <a href="https://www.bbc.co.uk/news/uk-england-dorset-41914141">photographs of English seaside life spanning three decades</a> are just some of the historical documents recorded on acetate film that are suffering irreversible damage due to what’s known as vinegar syndrome.</p> <p>Vinegar syndrome happens when acetate film is stored in a warm, humid room. These conditions cause the film to decompose. As the film starts to rot, it gives off acetic acid, the same ingredient in household vinegar that gives its distinctive smell and taste. The acid speeds up degradation in the affected film, and can even damage metal storage containers and other films stored nearby.</p> <p>Vinegar syndrome cannot be prevented forever, nor can it be reversed. It can only be delayed. This is why archives store their film collections in a cold and dry environment. Film stored in these conditions was expected to last for hundreds of years before vinegar syndrome started to set in. But my colleagues and I have <a href="https://www.sciencedirect.com/science/article/pii/S0141391019303787?via%253Dihub">recently shown</a> that these forecasts are overconfident, and that countless acetate films are facing imminent destruction.</p> <p>Current guidelines suggest that film stored in the same conditions could last about 450 years. For films made in 1950, when acetate films were becoming popular, this implies that vinegar syndrome won’t develop until about the year 2400.</p><div class="slot clear" data-id="17"> <div class="inline-promos-skeleton"> <h5></h5> <button></button> </div> </div> <p>But our research predicts that films stored in recommended conditions may last as little as 70 years before developing vinegar syndrome. According to our model, a film produced in 1950 and stored in the recommended conditions since then could develop vinegar syndrome this year.</p> <h2>Modelling film degradation</h2> <p>To understand how film might degrade over long periods of time, scientists perform experiments on film at high temperatures and relative humidity. These are called accelerated or artificial ageing experiments. The scientists take measurements of a feature that is considered a relevant indicator of degradation in the film.</p> <p>A common measurement is <a href="https://ieeexplore.ieee.org/document/7240670">free acidity</a>, which is different from pH. This gives a more sensitive measure of the amount of acetic acid that has built up in the film. Vinegar syndrome is considered to start when the free acidity reaches a level of 0.5.</p> <p>Measuring the free acidity over time, the artificial ageing experiments build a picture of how long it takes for film to develop vinegar syndrome in hot, humid conditions. Scientists can use the results of these experiments to estimate how milder conditions that are more similar to the environment found in archives will affect the film.</p> <p>As noted, the acid speeds up degradation in the film, including the chemical reaction that produces the acid in the first place. If film is stored in a closed container that prevents acid from escaping (often the case with film frequently stored in metal or plastic cans), this can result in an <a href="https://theconversation.com/coronavirus-is-growing-exponentially-heres-what-that-really-means-134591">exponential rise</a> in acid levels over time.</p> <p>In the early stages of degradation, acid levels are low and this trend is not apparent. This has meant that, in <a href="https://ieeexplore.ieee.org/abstract/document/7240670">previous studies</a>, researchers assumed that during the early stages of a film’s lifetime, acidity levels were too low to affect film degradation. Earlier models therefore did not account for the effect of acid on the degradation rate from the beginning.</p> <figure class="align-center "> <div class="placeholder-container" style="--aspect-ratio-percent:74.93368700265252%;--background-color:#232c43"><img alt="" class="lazyload" data-src="https://images.theconversation.com/files/335987/original/file-20200519-152344-sfzi6e.jpg?ixlib=rb-4.1.0&q=45&auto=format&w=754&fit=clip" data-srcset="https://images.theconversation.com/files/335987/original/file-20200519-152344-sfzi6e.jpg?ixlib=rb-4.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335987/original/file-20200519-152344-sfzi6e.jpg?ixlib=rb-4.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335987/original/file-20200519-152344-sfzi6e.jpg?ixlib=rb-4.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335987/original/file-20200519-152344-sfzi6e.jpg?ixlib=rb-4.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335987/original/file-20200519-152344-sfzi6e.jpg?ixlib=rb-4.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335987/original/file-20200519-152344-sfzi6e.jpg?ixlib=rb-4.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></div> <figcaption> <span class="caption">Chemical additives from the film can start to form microscopic crystals on the surface when decay sets in.</span> <span class="attribution"><span class="source">Ida Ahmad</span>, <span class="license">Author provided</span></span> </figcaption> </figure> <p>A <a href="https://www.sciencedirect.com/science/article/pii/S0141391013004060">more recent study</a> from the British Library challenged the assumption that acid does not influence film degradation from the beginning. It found no evidence to support that the chemical mechanism changes when the acidity reaches a level of 0.5.</p> <p><a href="https://www.sciencedirect.com/science/article/pii/S0141391019303787?via%253Dihub">Our study</a> proposed a model to account for the effect of acid during the whole of the degradation process, including the early stages. We used <a href="https://ieeexplore.ieee.org/abstract/document/7236149">data from</a> <a href="https://scholar.google.com/scholar?cluster=14999661807443839975&hl=en&as_sdt=2005&sciodt=0,5">two studies</a> from the Image Permanence Institute in the US to develop and validate the model. We then used the model to make forecasts about film stability under typical archive conditions. These forecasts were compared with commonly used <a href="https://filmcare.org/pdf/acetate_guide.pdf">guidelines</a> in film preservation.</p> <p>Acetate films were widely adopted from the 1950s to 1980s, so it is likely that a large proportion of photographic records from this period are at risk. For example, the <a href="http://cullinanstudio.com/project/bfi-master-film-store">BFI Master Collection</a> consists of over 450,000 cans of film, of which 59% are acetate films. One of the biggest dangers of film exhibiting vinegar syndrome is that if not properly stored, the acid fumes may spread to other films. Just one reel of severely degrading acetate film could cause serious damage to the rest of the collection if the vinegar syndrome is not contained. </p> <p>There are three basic <a href="https://www.ironmountain.com/resources/general-articles/v/vinegar-syndrome-when-bad-things-happen-to-good-documents">strategies</a> for dealing with vinegar syndrome:</p> <ol> <li><p>Improve storage conditions by reducing moisture and lowering the temperature.</p></li> <li><p>Quarantine any films identified as having vinegar syndrome to prevent the spread.</p></li> <li><p>Duplicate the film or convert it to a digital medium.</p></li> </ol> <p>The damage done by vinegar syndrome is irreversible, and will eventually make the film unsalvageable, so it is best to follow the above tips. Researchers at Queen Mary University of London were recently able to recover images from an afflicted film reel, which was too brittle and fused together to be unwound, using an X-ray <a href="https://www.bbc.co.uk/rd/blog/2017-12-morecambe-wise-video-film-archive-restoration">scanning technique</a>. However, this method would not be possible at scale. </p> <p>Archives use guidelines to plan their film preservation strategy. For large collections, storing film in cold vaults is much cheaper than copying. If cold storage really could delay vinegar syndrome until 2400, then copying is not urgent. However, the new model predicts that vinegar syndrome will happen much sooner. We may only have a few more years, not a few centuries, to act before these films are lost forever.</p> </div> <div class="grid-ten grid-prepend-two large-grid-nine grid-last content-topics topic-list"> <i class="icon-tag"></i> <ul> <li class="topic-list-item"> <a href="/topics/chemistry-730">Chemistry</a> </li> <li class="topic-list-item"> <a href="/topics/film-1175">Film</a> </li> <li class="topic-list-item"> <a href="/topics/film-archives-84023">Film archives</a> </li> </ul> </div> </div> <div class="slot grid-ten grid-prepend-two large-grid-nine grid-last mb5" data-id="15"></div> </div> <div class="wrapper"> <div class="react-content-related-container" data-article-id="131712"></div> </div> </article> <div id="comments-container"></div> <div class="page-addendum"> <div class="wrapper"> <div class="grid-eight"> <div id="addendum-events-list" class="addendum-block jobs-events-list events"> <h3 class="border slammed">Events</h3> <ul> </ul> <a class="view-more" href="/global/events"> 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s=this.observers[e].get(t)||0;this.observers[e].set(t,s+1)})),this}off(e,t){this.observers[e]&&(t?this.observers[e].delete(t):delete this.observers[e])}emit(e){for(var t=arguments.length,s=new Array(t>1?t-1:0),i=1;i<t;i++)s[i-1]=arguments[i];if(this.observers[e]){Array.from(this.observers[e].entries()).forEach((e=>{let[t,i]=e;for(let e=0;e<i;e++)t(...s)}))}if(this.observers["*"]){Array.from(this.observers["*"].entries()).forEach((t=>{let[i,n]=t;for(let t=0;t<n;t++)i.apply(i,[e,...s])}))}}}class w extends O{constructor(e){let t=arguments.length>1&&void 0!==arguments[1]?arguments[1]:{ns:["translation"],defaultNS:"translation"};super(),this.data=e||{},this.options=t,void 0===this.options.keySeparator&&(this.options.keySeparator="."),void 0===this.options.ignoreJSONStructure&&(this.options.ignoreJSONStructure=!0)}addNamespaces(e){this.options.ns.indexOf(e)<0&&this.options.ns.push(e)}removeNamespaces(e){const t=this.options.ns.indexOf(e);t>-1&&this.options.ns.splice(t,1)}getResource(e,t,s){let n=arguments.length>3&&void 0!==arguments[3]?arguments[3]:{};const o=void 0!==n.keySeparator?n.keySeparator:this.options.keySeparator,r=void 0!==n.ignoreJSONStructure?n.ignoreJSONStructure:this.options.ignoreJSONStructure;let a;e.indexOf(".")>-1?a=e.split("."):(a=[e,t],s&&(Array.isArray(s)?a.push(...s):i(s)&&o?a.push(...s.split(o)):a.push(s)));const l=h(this.data,a);return!l&&!t&&!s&&e.indexOf(".")>-1&&(e=a[0],t=a[1],s=a.slice(2).join(".")),!l&&r&&i(s)?y(this.data?.[e]?.[t],s,o):l}addResource(e,t,s,i){let n=arguments.length>4&&void 0!==arguments[4]?arguments[4]:{silent:!1};const o=void 0!==n.keySeparator?n.keySeparator:this.options.keySeparator;let r=[e,t];s&&(r=r.concat(o?s.split(o):s)),e.indexOf(".")>-1&&(r=e.split("."),i=t,t=r[1]),this.addNamespaces(t),u(this.data,r,i),n.silent||this.emit("added",e,t,s,i)}addResources(e,t,s){let n=arguments.length>3&&void 0!==arguments[3]?arguments[3]:{silent:!1};for(const n in s)(i(s[n])||Array.isArray(s[n]))&&this.addResource(e,t,n,s[n],{silent:!0});n.silent||this.emit("added",e,t,s)}addResourceBundle(e,t,s,i,n){let o=arguments.length>5&&void 0!==arguments[5]?arguments[5]:{silent:!1,skipCopy:!1},r=[e,t];e.indexOf(".")>-1&&(r=e.split("."),i=s,s=t,t=r[1]),this.addNamespaces(t);let a=h(this.data,r)||{};o.skipCopy||(s=JSON.parse(JSON.stringify(s))),i?p(a,s,n):a={...a,...s},u(this.data,r,a),o.silent||this.emit("added",e,t,s)}removeResourceBundle(e,t){this.hasResourceBundle(e,t)&&delete this.data[e][t],this.removeNamespaces(t),this.emit("removed",e,t)}hasResourceBundle(e,t){return void 0!==this.getResource(e,t)}getResourceBundle(e,t){return t||(t=this.options.defaultNS),this.getResource(e,t)}getDataByLanguage(e){return this.data[e]}hasLanguageSomeTranslations(e){const t=this.getDataByLanguage(e);return!!(t&&Object.keys(t)||[]).find((e=>t[e]&&Object.keys(t[e]).length>0))}toJSON(){return this.data}}var L={processors:{},addPostProcessor(e){this.processors[e.name]=e},handle(e,t,s,i,n){return e.forEach((e=>{t=this.processors[e]?.process(t,s,i,n)??t})),t}};const R={};class P extends O{constructor(e){let t=arguments.length>1&&void 0!==arguments[1]?arguments[1]:{};super(),((e,t,s)=>{e.forEach((e=>{t[e]&&(s[e]=t[e])}))})(["resourceStore","languageUtils","pluralResolver","interpolator","backendConnector","i18nFormat","utils"],e,this),this.options=t,void 0===this.options.keySeparator&&(this.options.keySeparator="."),this.logger=S.create("translator")}changeLanguage(e){e&&(this.language=e)}exists(e){let t=arguments.length>1&&void 0!==arguments[1]?arguments[1]:{interpolation:{}};if(null==e)return!1;const s=this.resolve(e,t);return void 0!==s?.res}extractFromKey(e,t){let s=void 0!==t.nsSeparator?t.nsSeparator:this.options.nsSeparator;void 0===s&&(s=":");const n=void 0!==t.keySeparator?t.keySeparator:this.options.keySeparator;let o=t.ns||this.options.defaultNS||[];const r=s&&e.indexOf(s)>-1,a=!(this.options.userDefinedKeySeparator||t.keySeparator||this.options.userDefinedNsSeparator||t.nsSeparator||((e,t,s)=>{t=t||"",s=s||"";const i=v.filter((e=>t.indexOf(e)<0&&s.indexOf(e)<0));if(0===i.length)return!0;const n=m.getRegExp(`(${i.map((e=>"?"===e?"\\?":e)).join("|")})`);let o=!n.test(e);if(!o){const t=e.indexOf(s);t>0&&!n.test(e.substring(0,t))&&(o=!0)}return o})(e,s,n));if(r&&!a){const t=e.match(this.interpolator.nestingRegexp);if(t&&t.length>0)return{key:e,namespaces:i(o)?[o]:o};const r=e.split(s);(s!==n||s===n&&this.options.ns.indexOf(r[0])>-1)&&(o=r.shift()),e=r.join(n)}return{key:e,namespaces:i(o)?[o]:o}}translate(e,t,s){if("object"!=typeof t&&this.options.overloadTranslationOptionHandler&&(t=this.options.overloadTranslationOptionHandler(arguments)),"object"==typeof t&&(t={...t}),t||(t={}),null==e)return"";Array.isArray(e)||(e=[String(e)]);const n=void 0!==t.returnDetails?t.returnDetails:this.options.returnDetails,o=void 0!==t.keySeparator?t.keySeparator:this.options.keySeparator,{key:r,namespaces:a}=this.extractFromKey(e[e.length-1],t),l=a[a.length-1],c=t.lng||this.language,u=t.appendNamespaceToCIMode||this.options.appendNamespaceToCIMode;if("cimode"===c?.toLowerCase()){if(u){const e=t.nsSeparator||this.options.nsSeparator;return n?{res:`${l}${e}${r}`,usedKey:r,exactUsedKey:r,usedLng:c,usedNS:l,usedParams:this.getUsedParamsDetails(t)}:`${l}${e}${r}`}return n?{res:r,usedKey:r,exactUsedKey:r,usedLng:c,usedNS:l,usedParams:this.getUsedParamsDetails(t)}:r}const h=this.resolve(e,t);let p=h?.res;const d=h?.usedKey||r,g=h?.exactUsedKey||r,f=Object.prototype.toString.apply(p),v=void 0!==t.joinArrays?t.joinArrays:this.options.joinArrays,m=!this.i18nFormat||this.i18nFormat.handleAsObject,y=!i(p)&&"boolean"!=typeof p&&"number"!=typeof p;if(!(m&&p&&y&&["[object Number]","[object Function]","[object RegExp]"].indexOf(f)<0)||i(v)&&Array.isArray(p))if(m&&i(v)&&Array.isArray(p))p=p.join(v),p&&(p=this.extendTranslation(p,e,t,s));else{let n=!1,a=!1;const u=void 0!==t.count&&!i(t.count),d=P.hasDefaultValue(t),g=u?this.pluralResolver.getSuffix(c,t.count,t):"",f=t.ordinal&&u?this.pluralResolver.getSuffix(c,t.count,{ordinal:!1}):"",v=u&&!t.ordinal&&0===t.count,m=v&&t[`defaultValue${this.options.pluralSeparator}zero`]||t[`defaultValue${g}`]||t[`defaultValue${f}`]||t.defaultValue;!this.isValidLookup(p)&&d&&(n=!0,p=m),this.isValidLookup(p)||(a=!0,p=r);const y=(t.missingKeyNoValueFallbackToKey||this.options.missingKeyNoValueFallbackToKey)&&a?void 0:p,b=d&&m!==p&&this.options.updateMissing;if(a||n||b){if(this.logger.log(b?"updateKey":"missingKey",c,l,r,b?m:p),o){const e=this.resolve(r,{...t,keySeparator:!1});e&&e.res&&this.logger.warn("Seems the loaded translations were in flat JSON format instead of nested. Either set keySeparator: false on init or make sure your translations are published in nested format.")}let e=[];const s=this.languageUtils.getFallbackCodes(this.options.fallbackLng,t.lng||this.language);if("fallback"===this.options.saveMissingTo&&s&&s[0])for(let t=0;t<s.length;t++)e.push(s[t]);else"all"===this.options.saveMissingTo?e=this.languageUtils.toResolveHierarchy(t.lng||this.language):e.push(t.lng||this.language);const i=(e,s,i)=>{const n=d&&i!==p?i:y;this.options.missingKeyHandler?this.options.missingKeyHandler(e,l,s,n,b,t):this.backendConnector?.saveMissing&&this.backendConnector.saveMissing(e,l,s,n,b,t),this.emit("missingKey",e,l,s,p)};this.options.saveMissing&&(this.options.saveMissingPlurals&&u?e.forEach((e=>{const s=this.pluralResolver.getSuffixes(e,t);v&&t[`defaultValue${this.options.pluralSeparator}zero`]&&s.indexOf(`${this.options.pluralSeparator}zero`)<0&&s.push(`${this.options.pluralSeparator}zero`),s.forEach((s=>{i([e],r+s,t[`defaultValue${s}`]||m)}))})):i(e,r,m))}p=this.extendTranslation(p,e,t,h,s),a&&p===r&&this.options.appendNamespaceToMissingKey&&(p=`${l}:${r}`),(a||n)&&this.options.parseMissingKeyHandler&&(p=this.options.parseMissingKeyHandler(this.options.appendNamespaceToMissingKey?`${l}:${r}`:r,n?p:void 0))}else{if(!t.returnObjects&&!this.options.returnObjects){this.options.returnedObjectHandler||this.logger.warn("accessing an object - but returnObjects options is not enabled!");const e=this.options.returnedObjectHandler?this.options.returnedObjectHandler(d,p,{...t,ns:a}):`key '${r} (${this.language})' returned an object instead of string.`;return n?(h.res=e,h.usedParams=this.getUsedParamsDetails(t),h):e}if(o){const e=Array.isArray(p),s=e?[]:{},i=e?g:d;for(const e in p)if(Object.prototype.hasOwnProperty.call(p,e)){const n=`${i}${o}${e}`;s[e]=this.translate(n,{...t,joinArrays:!1,ns:a}),s[e]===n&&(s[e]=p[e])}p=s}}return n?(h.res=p,h.usedParams=this.getUsedParamsDetails(t),h):p}extendTranslation(e,t,s,n,o){var r=this;if(this.i18nFormat?.parse)e=this.i18nFormat.parse(e,{...this.options.interpolation.defaultVariables,...s},s.lng||this.language||n.usedLng,n.usedNS,n.usedKey,{resolved:n});else if(!s.skipInterpolation){s.interpolation&&this.interpolator.init({...s,interpolation:{...this.options.interpolation,...s.interpolation}});const a=i(e)&&(void 0!==s?.interpolation?.skipOnVariables?s.interpolation.skipOnVariables:this.options.interpolation.skipOnVariables);let l;if(a){const t=e.match(this.interpolator.nestingRegexp);l=t&&t.length}let c=s.replace&&!i(s.replace)?s.replace:s;if(this.options.interpolation.defaultVariables&&(c={...this.options.interpolation.defaultVariables,...c}),e=this.interpolator.interpolate(e,c,s.lng||this.language||n.usedLng,s),a){const t=e.match(this.interpolator.nestingRegexp);l<(t&&t.length)&&(s.nest=!1)}!s.lng&&n&&n.res&&(s.lng=this.language||n.usedLng),!1!==s.nest&&(e=this.interpolator.nest(e,(function(){for(var e=arguments.length,i=new Array(e),n=0;n<e;n++)i[n]=arguments[n];return o?.[0]!==i[0]||s.context?r.translate(...i,t):(r.logger.warn(`It seems you are nesting recursively key: ${i[0]} in key: ${t[0]}`),null)}),s)),s.interpolation&&this.interpolator.reset()}const a=s.postProcess||this.options.postProcess,l=i(a)?[a]:a;return null!=e&&l?.length&&!1!==s.applyPostProcessor&&(e=L.handle(l,e,t,this.options&&this.options.postProcessPassResolved?{i18nResolved:{...n,usedParams:this.getUsedParamsDetails(s)},...s}:s,this)),e}resolve(e){let t,s,n,o,r,a=arguments.length>1&&void 0!==arguments[1]?arguments[1]:{};return i(e)&&(e=[e]),e.forEach((e=>{if(this.isValidLookup(t))return;const l=this.extractFromKey(e,a),c=l.key;s=c;let u=l.namespaces;this.options.fallbackNS&&(u=u.concat(this.options.fallbackNS));const h=void 0!==a.count&&!i(a.count),p=h&&!a.ordinal&&0===a.count,d=void 0!==a.context&&(i(a.context)||"number"==typeof a.context)&&""!==a.context,g=a.lngs?a.lngs:this.languageUtils.toResolveHierarchy(a.lng||this.language,a.fallbackLng);u.forEach((e=>{this.isValidLookup(t)||(r=e,R[`${g[0]}-${e}`]||!this.utils?.hasLoadedNamespace||this.utils?.hasLoadedNamespace(r)||(R[`${g[0]}-${e}`]=!0,this.logger.warn(`key "${s}" for languages "${g.join(", ")}" won't get resolved as namespace "${r}" was not yet loaded`,"This means something IS WRONG in your setup. You access the t function before i18next.init / i18next.loadNamespace / i18next.changeLanguage was done. Wait for the callback or Promise to resolve before accessing it!!!")),g.forEach((s=>{if(this.isValidLookup(t))return;o=s;const i=[c];if(this.i18nFormat?.addLookupKeys)this.i18nFormat.addLookupKeys(i,c,s,e,a);else{let e;h&&(e=this.pluralResolver.getSuffix(s,a.count,a));const t=`${this.options.pluralSeparator}zero`,n=`${this.options.pluralSeparator}ordinal${this.options.pluralSeparator}`;if(h&&(i.push(c+e),a.ordinal&&0===e.indexOf(n)&&i.push(c+e.replace(n,this.options.pluralSeparator)),p&&i.push(c+t)),d){const s=`${c}${this.options.contextSeparator}${a.context}`;i.push(s),h&&(i.push(s+e),a.ordinal&&0===e.indexOf(n)&&i.push(s+e.replace(n,this.options.pluralSeparator)),p&&i.push(s+t))}}let r;for(;r=i.pop();)this.isValidLookup(t)||(n=r,t=this.getResource(s,e,r,a))})))}))})),{res:t,usedKey:s,exactUsedKey:n,usedLng:o,usedNS:r}}isValidLookup(e){return!(void 0===e||!this.options.returnNull&&null===e||!this.options.returnEmptyString&&""===e)}getResource(e,t,s){let i=arguments.length>3&&void 0!==arguments[3]?arguments[3]:{};return this.i18nFormat?.getResource?this.i18nFormat.getResource(e,t,s,i):this.resourceStore.getResource(e,t,s,i)}getUsedParamsDetails(){let e=arguments.length>0&&void 0!==arguments[0]?arguments[0]:{};const t=["defaultValue","ordinal","context","replace","lng","lngs","fallbackLng","ns","keySeparator","nsSeparator","returnObjects","returnDetails","joinArrays","postProcess","interpolation"],s=e.replace&&!i(e.replace);let n=s?e.replace:e;if(s&&void 0!==e.count&&(n.count=e.count),this.options.interpolation.defaultVariables&&(n={...this.options.interpolation.defaultVariables,...n}),!s){n={...n};for(const e of t)delete n[e]}return n}static hasDefaultValue(e){const t="defaultValue";for(const s in e)if(Object.prototype.hasOwnProperty.call(e,s)&&t===s.substring(0,12)&&void 0!==e[s])return!0;return!1}}class j{constructor(e){this.options=e,this.supportedLngs=this.options.supportedLngs||!1,this.logger=S.create("languageUtils")}getScriptPartFromCode(e){if(!(e=b(e))||e.indexOf("-")<0)return null;const t=e.split("-");return 2===t.length?null:(t.pop(),"x"===t[t.length-1].toLowerCase()?null:this.formatLanguageCode(t.join("-")))}getLanguagePartFromCode(e){if(!(e=b(e))||e.indexOf("-")<0)return e;const t=e.split("-");return this.formatLanguageCode(t[0])}formatLanguageCode(e){if(i(e)&&e.indexOf("-")>-1){let t=Intl.getCanonicalLocales(e)[0];return t&&this.options.lowerCaseLng&&(t=t.toLowerCase()),t||(this.options.lowerCaseLng?e.toLowerCase():e)}return this.options.cleanCode||this.options.lowerCaseLng?e.toLowerCase():e}isSupportedCode(e){return("languageOnly"===this.options.load||this.options.nonExplicitSupportedLngs)&&(e=this.getLanguagePartFromCode(e)),!this.supportedLngs||!this.supportedLngs.length||this.supportedLngs.indexOf(e)>-1}getBestMatchFromCodes(e){if(!e)return null;let t;return e.forEach((e=>{if(t)return;const s=this.formatLanguageCode(e);this.options.supportedLngs&&!this.isSupportedCode(s)||(t=s)})),!t&&this.options.supportedLngs&&e.forEach((e=>{if(t)return;const s=this.getLanguagePartFromCode(e);if(this.isSupportedCode(s))return t=s;t=this.options.supportedLngs.find((e=>e===s?e:e.indexOf("-")<0&&s.indexOf("-")<0?void 0:e.indexOf("-")>0&&s.indexOf("-")<0&&e.substring(0,e.indexOf("-"))===s||0===e.indexOf(s)&&s.length>1?e:void 0))})),t||(t=this.getFallbackCodes(this.options.fallbackLng)[0]),t}getFallbackCodes(e,t){if(!e)return[];if("function"==typeof e&&(e=e(t)),i(e)&&(e=[e]),Array.isArray(e))return e;if(!t)return e.default||[];let s=e[t];return s||(s=e[this.getScriptPartFromCode(t)]),s||(s=e[this.formatLanguageCode(t)]),s||(s=e[this.getLanguagePartFromCode(t)]),s||(s=e.default),s||[]}toResolveHierarchy(e,t){const s=this.getFallbackCodes(t||this.options.fallbackLng||[],e),n=[],o=e=>{e&&(this.isSupportedCode(e)?n.push(e):this.logger.warn(`rejecting language code not found in supportedLngs: ${e}`))};return i(e)&&(e.indexOf("-")>-1||e.indexOf("_")>-1)?("languageOnly"!==this.options.load&&o(this.formatLanguageCode(e)),"languageOnly"!==this.options.load&&"currentOnly"!==this.options.load&&o(this.getScriptPartFromCode(e)),"currentOnly"!==this.options.load&&o(this.getLanguagePartFromCode(e))):i(e)&&o(this.formatLanguageCode(e)),s.forEach((e=>{n.indexOf(e)<0&&o(this.formatLanguageCode(e))})),n}}const $={zero:0,one:1,two:2,few:3,many:4,other:5},C={select:e=>1===e?"one":"other",resolvedOptions:()=>({pluralCategories:["one","other"]})};class N{constructor(e){let t=arguments.length>1&&void 0!==arguments[1]?arguments[1]:{};this.languageUtils=e,this.options=t,this.logger=S.create("pluralResolver"),this.pluralRulesCache={}}addRule(e,t){this.rules[e]=t}clearCache(){this.pluralRulesCache={}}getRule(e){let t=arguments.length>1&&void 0!==arguments[1]?arguments[1]:{};const 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0,this.setResolvedLanguage(e)},a=(e,i)=>{i?(r(i),this.translator.changeLanguage(i),this.isLanguageChangingTo=void 0,this.emit("languageChanged",i),this.logger.log("languageChanged",i)):this.isLanguageChangingTo=void 0,o.resolve((function(){return s.t(...arguments)})),t&&t(e,(function(){return s.t(...arguments)}))},l=t=>{e||t||!this.services.languageDetector||(t=[]);const s=i(t)?t:this.services.languageUtils.getBestMatchFromCodes(t);s&&(this.language||r(s),this.translator.language||this.translator.changeLanguage(s),this.services.languageDetector?.cacheUserLanguage?.(s)),this.loadResources(s,(e=>{a(e,s)}))};return e||!this.services.languageDetector||this.services.languageDetector.async?!e&&this.services.languageDetector&&this.services.languageDetector.async?0===this.services.languageDetector.detect.length?this.services.languageDetector.detect().then(l):this.services.languageDetector.detect(l):l(e):l(this.services.languageDetector.detect()),o}getFixedT(e,t,s){var n=this;const o=function(e,t){let i;if("object"!=typeof t){for(var r=arguments.length,a=new Array(r>2?r-2:0),l=2;l<r;l++)a[l-2]=arguments[l];i=n.options.overloadTranslationOptionHandler([e,t].concat(a))}else i={...t};i.lng=i.lng||o.lng,i.lngs=i.lngs||o.lngs,i.ns=i.ns||o.ns,""!==i.keyPrefix&&(i.keyPrefix=i.keyPrefix||s||o.keyPrefix);const c=n.options.keySeparator||".";let u;return u=i.keyPrefix&&Array.isArray(e)?e.map((e=>`${i.keyPrefix}${c}${e}`)):i.keyPrefix?`${i.keyPrefix}${c}${e}`:e,n.t(u,i)};return i(e)?o.lng=e:o.lngs=e,o.ns=t,o.keyPrefix=s,o}t(){for(var e=arguments.length,t=new Array(e),s=0;s<e;s++)t[s]=arguments[s];return this.translator?.translate(...t)}exists(){for(var e=arguments.length,t=new Array(e),s=0;s<e;s++)t[s]=arguments[s];return this.translator?.exists(...t)}setDefaultNamespace(e){this.options.defaultNS=e}hasLoadedNamespace(e){let t=arguments.length>1&&void 0!==arguments[1]?arguments[1]:{};if(!this.isInitialized)return this.logger.warn("hasLoadedNamespace: i18next was not 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o=this.options.preload||[],r=e.filter((e=>o.indexOf(e)<0&&this.services.languageUtils.isSupportedCode(e)));return r.length?(this.options.preload=o.concat(r),this.loadResources((e=>{s.resolve(),t&&t(e)})),s):(t&&t(),Promise.resolve())}dir(e){if(e||(e=this.resolvedLanguage||(this.languages?.length>0?this.languages[0]:this.language)),!e)return"rtl";const t=this.services?.languageUtils||new j(F());return["ar","shu","sqr","ssh","xaa","yhd","yud","aao","abh","abv","acm","acq","acw","acx","acy","adf","ads","aeb","aec","afb","ajp","apc","apd","arb","arq","ars","ary","arz","auz","avl","ayh","ayl","ayn","ayp","bbz","pga","he","iw","ps","pbt","pbu","pst","prp","prd","ug","ur","ydd","yds","yih","ji","yi","hbo","men","xmn","fa","jpr","peo","pes","prs","dv","sam","ckb"].indexOf(t.getLanguagePartFromCode(e))>-1||e.toLowerCase().indexOf("-arab")>1?"rtl":"ltr"}static createInstance(){return new H(arguments.length>0&&void 0!==arguments[0]?arguments[0]:{},arguments.length>1?arguments[1]:void 0)}cloneInstance(){let e=arguments.length>0&&void 0!==arguments[0]?arguments[0]:{},t=arguments.length>1&&void 0!==arguments[1]?arguments[1]:U;const s=e.forkResourceStore;s&&delete e.forkResourceStore;const i={...this.options,...e,isClone:!0},n=new H(i);void 0===e.debug&&void 0===e.prefix||(n.logger=n.logger.clone(e));return["store","services","language"].forEach((e=>{n[e]=this[e]})),n.services={...this.services},n.services.utils={hasLoadedNamespace:n.hasLoadedNamespace.bind(n)},s&&(n.store=new w(this.store.data,i),n.services.resourceStore=n.store),n.translator=new P(n.services,i),n.translator.on("*",(function(e){for(var t=arguments.length,s=new Array(t>1?t-1:0),i=1;i<t;i++)s[i-1]=arguments[i];n.emit(e,...s)})),n.init(i,t),n.translator.options=i,n.translator.backendConnector.services.utils={hasLoadedNamespace:n.hasLoadedNamespace.bind(n)},n}toJSON(){return{options:this.options,store:this.store,language:this.language,languages:this.languages,resolvedLanguage:this.resolvedLanguage}}}const K=H.createInstance();K.createInstance=H.createInstance;K.createInstance,K.dir,K.init,K.loadResources,K.reloadResources,K.use,K.changeLanguage,K.getFixedT,K.t,K.exists,K.setDefaultNamespace,K.hasLoadedNamespace,K.loadNamespaces,K.loadLanguages}},function(e){var t;t=51250,e(e.s=t)}]); //# sourceMappingURL=i18n_init-115e8b97572e00d91d6f.js.map //]]> </script> <script src="https://cdn.theconversation.com/static/tc/runtime-8563a1641acaeb567def.js"></script> <script type="text/javascript" data-vendor="c:smartocto-GJ7CA7CP"> var _ain = { access_level: "free", article_type: "analysis", authors: "UCL", id: "2743", maincontent: ".content-body", postid: "131712", pubdate: "2020-05-19T07:30:24Z", reader_type: "anonymous", sections: "uk>Science + Tech", tags: "Chemistry, Film, Film archives, Vinegar syndrome", title: "Historical films may be decaying much faster than we thought thanks to 'vinegar syndrome'", }; (function (d, s) { var sf = d.createElement(s); sf.type = 'text/javascript'; sf.async = 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