Agents of Deterioration: Physical Forces

This is the beginning of a new series that I’ve been meaning to make for a long time now, and it’s something super important not just to conservation, but it’s also important to have a basic understanding of in archaeology as well: The Agents of Deterioration!! The agents of deterioration are essentially the pillars of preventive conservation. They’re the things that haunt you late at night, making you wonder if you forgot one, and if you’ll go in to storage the next day and find an infestation of bats has suddenly taken up residence in the tapestry section, or a flash flood has waterlogged everything!

The Agents of deterioration are essentially what their title describes them to be: factors that contribute to the deterioration of a cultural heritage object. The Canadian Conservation Institute has created the ultimate resource for these, and it’s freely available on their website, but I wanted to make videos that summarised everything because… well that’s what I do!

The first agent we’re going to be discussing is: Physical Forces!

A physical force is something that physically happens directly to an artefact. So handling, dropping, shipping, earthquakes, explosions, accidentally causing a fresh break in a piece of pottery with your pickaxe while excavating… think of things that physically affect and object. Physical forces can cause damages like compression, tears, cracks, scratches, dents, abrasions, everything like that. Don’t forget that gravity is a physical force that may have an effect on an object’s well being. It’s a constant force on everything, and supports you use on an object may deform an object because the load of gravity may not be placed properly.

There are 5 forces we need to take into account: impact, shock, vibrations, pressure, and abrasion.

Impact

Impact is the result of something striking an object. This could be an object striking a hard surface, or two objects coming into contact with each other. And of course, there are different types of impact. You could have a concentrated hit, that only causes localized damage like a crack, or you could have a more spread out impact that affects the object in a larger way. Don’t forget that localized impact like those small cracks can increase an object’s susceptibility to force in the future.

Shock

Shock is the result of a strong impact, which can produce a lot of strain or even deform an object. Shock can cause TONNES of damage, and it’s the most important thing to consider when transporting an object because it’s the top cause of damage in that situation.

Shock is the energetic response of an object. Low levels of shock may be absorbed and spread throughout the object without damage because it dissipates, but then impact may cause movement in the object and it could collide with other parts of itself or with other objects. Higher shock levels can cause the object to move and induce a lot of strain that is higher than its normal thresholds. Shock effects can accumulate over time, but if the shock is high enough, damage will occur in one single event.

Vibration

Vibration is the oscillating motion of an object, in relation to a fixed point of reference. With vibration, the most important thing to consider is type of vibration. Many objects with you know, extending pieces, moving pieces or free-hanging pieces can be very prone to vibration. The main things to be concerned about with vibration are its frequency and amplitude. You want to know how often the vibration waves are happening, and how strong they are. Obviously if the vibration is low and infrequent, it’s not very worrisome, whereas if it’s random vibration like with most everyday things, and with transport trucks, you would need to be more concerned and aware of the risk to your object.

Vibration can come from a lot of things, like transportation, construction vibration, and sound vibration.

Vibration can have a lot of different effects on an object. Objects that are just sitting on a shelf can move, hit each other, or fall off the shelf completely. If an object has loose fitting pieces, vibration can shake them off, objects that are in a box and aren’t properly cushioned will hit each other and rattle around everywhere.

Some objects of course are more sensitive to vibrations than others. A large, heavy statue will be less susceptible to vibration in comparison to an antique clock with all its fine tuned moving parts.

Pressure

Pressure is pretty self-explanatory. It’s force applied to an object. This can be anything from gravity, to the pressure your hands place on an object while handling it. A good rule of thumb to minimize pressure is to expand the contact area, which will spread the pressure outwards, meaning a lower amount of pressure over a wider area instead of a high amount of pressure in one small area.

Abrasion

Abrasion is when two surfaces move against each other, like you scraping your knee on the ground when you trip on a European cobblestone during your run and eat dirt in front of everyone, but no one comes to help you because they’re practising social distancing. … anyways abrasion risk depends on the pressure between the two surfaces and the strength of the surfaces.

Again different object will have different susceptibility to abrasion. Thick glazed pottery has a lower chance of abrading in comparison to unfired clay or pastel paintings.

How Do We Protect Objects Against Physical Forces?

The best things are to practice proper, safe handling procedures, making sure you’re holding objects with two hands, never carrying it, but rather putting it on a padded rolling cart to move it from place to place. Make sure your shelves and cabinets are stable and the objects on them are separated and well padded. Objects in boxes should have their own little nesting place like this … so they’re well protected, and that way other objects won’t touch it either. Plus they just look beautiful. There’s something so oddly satisfying about a box that’s perfectly formatted to an object. It’s like placing the last piece of a puzzle.

When you’re transporting an object, make sure it’s well padded in a box with lots of foam, no other objects are loose, and that the boxes themselves are restrained in the back so they don’t move around either. If it has a delicate surface, you’ll probably want to protect that from the packing material as well. Essentially, you want to restrict the movement as much as possible, while still making sure you don’t restrict it so much that it causes unwanted pressure on the object.

Just use your common sense, and always think about what could happen for every action you do. You want to make a plan for everything you do, and always have the object’s safety at the center of it.

Of course, there are physical forces you really can’t escape. Earthquakes are things that we can protect against, but never completely. Museums and places that have high risk of seismic activity are of course always built with that protection in mind. I was in the acropolis museum in Athens when an earthquake hit and I was amazed how sturdy everything was. It was a small earthquake, but if they didn’t plan in advance, a lot of stuff would have fallen over and been damaged.

So there you have it, guys! The first agent of deterioration. Of course there’s a lot more detail that I could do in to, but that’s all written down for you on the CCI website, which you can visit here.

Have a question? Email me!

Sources

Canadian Conservation Institute: 10 Agents of Deteriorarion- Physical Forces by Paul Marcon https://www.canada.ca/en/conservation-institute/services/agents-deterioration/physical-forces.html

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Some days I pretend I'm Indiana Jones. Other days, I make videos about pretending to be Indiana Jones. 

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