How did the Iron Age begin in Britain?

The British Iron Age ran from around 800 BC until the invasion by the Romans in 43 AD who brought with them the technology to make steel, though this new tech took years to spread around the country.

Before the Iron Age was the Bronze Age, a time when the hardest metal that people could work with was a combination of tin and copper. Both of these metals have reasonably low melting points as metals go, with copper melting at 1,085 °C and tin melting much lower at 231.9 °C.

Both of these metals can be melted on a bonfire, especially if there’s some coal thrown in to make it hotter. To make metals in this way they would simply need to place some ore on a flat stone in the middle of the fire, and then pick it up with sticks to pour it out into a mold. During the earlier days of working with bronze, people would often make molds by carving a shape into a piece of wood and then pouring molten bronze from a bowl-shaped rock sitting in the fire. Over time they would be able to make hammers and anvils to shape and work the metal better, but the one thing they couldn’t do was melt Iron.

Iron has a melting temperature of 1,538 °C, a level of heat that’s way too high to achieve in any bonfire, no matter the size or what has been thrown onto it. The other problem was getting hold of the iron in the first place, and even though it’s not rare, the ore can be extremely difficult to hack out of solid rock using bronze tools.

So how did the Iron Age begin in Britain?

As for how the technology came to be, no one knows for sure. It could be due to a mysterious worldly traveler coming to the shores of Britain and showing the locals what he knew, or it could be that people simply worked it out.

The way to melt iron seemed to be as easy as continuously blowing air into the fire, and so the bellows were invented. This most likely came to be from people realizing that blowing air into a fire helps it become hotter momentarily, and a giant version of a lung blowing into a much bigger fire would create the necessary heat to melt iron.

Crude stone smelters were built by stacking stone sealed with clay, and a hole at the bottom allowed the air from the billows to come through. Stacking the inside of the smelter with alternating layers of ore and coal would help to increase the temperature, and after it became hot enough the liquid iron would melt out the bottom and run out onto the ground.

This setup would take nothing more than stone, clay, coal, and a couple of animal skins held together with wood, all of which the Britons had for thousands of years before someone realized putting them together could produce a new contraption to melt iron.

As for where they got Iron ore from in the first place the answer would most likely be from bogs. If you’ve ever been out walking in the countryside and seen a stream with rust red-colored mud or sand, then it’s most likely been caused by a nearby iron deposit rusting into the water.

If you see this strange color around a swamp or bog then you’ve got yourself a source of iron. When iron is within bog mud, the center of the ore becomes starved of water and oxygen and so only the outside would rust, leaving the center ripe for smelting.

After this new technology moved across the country it took many years until it became useful, as the first casting from iron ore is known as pig iron. The name comes from the way it was made, which was done by drawing a line in the soil starting at the point the metal would touch the ground and going in a straight line away from it, with ingot-shaped run-offs on either side. The pattern is supposed to look like piglets suckling from either side of their mother.

Pig iron contains a very high carbon content and is very brittle, to the point where it shatters almost like glass if struck. It needs to be melted a second time in order for the carbon content to be removed so it can become hard enough to be useful. After that, it needs to be worked and further purified, but when people worked this out is anyone’s guess.

The Iron Age ended in 43 AD when the Romans arrived and quickly conquered the country, spreading their knowledge of how to make steel. It took years for this new technology to spread across the country, but it didn’t make it into Scotland until 400 years after the Romans first arrived. Even with their advanced technology and huge army, the Romans were never able to conquer Scotland and ended up building two walls across the country in an attempt to keep them out, with the most famous of the two being Hadrian’s Wall.