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Agents of Deterioration: Fire

In December of 2020, I introduced a new series for 2021 on the ten agents of deterioration. In January, we discussed light damage, and how to mitigate the risks for items in your own collection. This month, we'll be talking about fire.

It's pretty self explanatory that fire is a catastrophic event regardless of the situation, with potential loss to lives, buildings, and collections. Fire can be completely preventable and avoidable, but unfortunately, it isn't the only item you have to worry about when trying to mitigate risks in your home. Not only does the fire itself cause unsalvageable damage to your belongings, but the smoke and soot, water from a sprinkler system or from the fire department, and fire extinguishers can all have lasting consequences on your treasures.

First, fire is a chemical reaction occurring when you have the following three elements combined in the right mixture: oxygen, heat, and fuel. The fuel source is basically anything than can burn; heat is the ignition source. All three of these are needed for a fire to spark and take hold. Remove one of these elements from a flame, and you stop the fire.

That's why they say throw a blanket on a small fire - you're removing the oxygen so it can't burn. The same goes with gas suppression systems installed in buildings. However, there's also three stages in which a fire takes hold (pre-flashover, flashover, and post-flashover)- if you catch it in the first two stages, damages and loss will be minimal.

Pre-flashover is the act of the fire igniting. This stage is when the fire is the most containable if caught quickly. Flashover is where combustible items in the same vicinity ignite, causing the fire to grow. Post-flashover is when the fire is fully formed and moving rapidly through the space. At this point, the fire department will need to step in, as it's out of control and can't be contained by someone by themselves.


As I mentioned earlier, of course the fire itself will destroy collections and other valuables, but fire isn't the only thing to worry about. There's a number of other factors as a result of the fire that can create chemical changes to your valuables, say if they're in a separate room that doesn't see a flame firsthand.


Fire gives off immense heat as it rages through spaces. Organic materials, if not wet, will ignite fairly quickly, further intensifying the fire in the post-flashover stage. Even inorganic materials will have chemical changes:

  • metals will melt or become brittle. Metal actually has a really high melting point, so the fire would have to be in a post-flashover stage for any significant damage to happen.

  • glazes on pottery can re-melt

  • ceramics can crack or explode - this is called thermal shock

  • glass will crack or shatter from the rise in temperature

Soot & Smoke

There's a slight difference between smoke and soot. Smoke is unburned particles left by the fire that migrate to colder areas. Soot is a fine black or brown powder that is ashy in consistency and is left behind by the fire. Soot can get rubbed into porous objects when they are handled post fire, and gets more difficult to remove the longer they objects sit. There's actually three different types of smoke, too, that have different effects on objects themselves. Wet smoke, when plastic and rubber are burned, leave a sticky and smeary mess. Dry smoke, where paper and wood are burned, migrates quickly upward, causing damage to rooms that may never even see any fire damage. Smoke residue, or protein fire residue, is virtually invisible, but discolors paints and varnishes on canvases, ceramics, or other similar objects.


We'll talk more about water in another post, but water can absolutely ruin organic materials, such as books, textiles, works on paper, etc. Add soot to the sprinkler or fire department firehose, and you've got a sludgy mixture that becomes increasingly more difficult to remove the longer it sits.


How can you mitigate these risks in your home?

  • Make sure your electrical wiring or your electrical system is up to date, and that wires won't short circuit.

  • Ensure that a fire can be detected at an early stage through a both smoke and fire alarm systems.

  • Keep fire extinguishers handy, and make sure they're up to date. Carbon dioxide extinguishers do less damage on items - historic or otherwise - than water.

  • Have dedicated spaces for flammable collections

There are some collections that are more at risk than others of spontaneously combusting, or furthering a flame if something else nearby is ignited. The biggest of these is cellulose nitrate film. This film was created and in wide use during the 19-teens, 1920s, and 1930s before 'safety film' or cellulose acetate film came into production. In extreme heat, cellulose nitrate films would combust, causing it and everything around it to also ignite. Think of the section in Inglorious Bastards when everyone is in the theatre...This is also why so many 19-teens and 1920s films are considered lost. The material is extremely volatile, and should be kept in a fire proof safe or room, as once it starts burning, it will. not. stop. Even doused in a bucket of water.

Check out this short clip of cellulose nitrate combustion, and just how volatile this material is. Don't blink, or you'll miss it!

Other flammable collections include ammunition, munitions, and 'wet' collections - natural history specimen collections stored in 70% alcohol and 30% water.


Check back at the beginning of next month for the next agent of deterioration: water. Until then though, there will be more textile related content, and hopefully another YouTube video :D

Happy February!

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