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Let's say you've gone back in time - Fixed*

The academically anemic infographic under discussion. Click for a larger image.
Time travel infographic in question.

I've seen this infographic (at right) posted several times on the internet. My inner engineer couldn't help but to tinker with it and give it that little something extra[0].  I'll dial it up to '11' by making it useful without writing a dissertation on each subject. Here goes...


Build an evaporative refrigerator - no moving parts, no electricity

How to build a Zeer pot
Zeer Pot Construction

What is an evaporative refrigerator?

It is a device that uses the evaporation to cool a space that can be used to store food or water. An illustration of one version is shown at right.   This version was created by putting one earthenware pot inside another, filling the space between them with sand and then wetting the sand.  Food is stored in the inner pot which can be covered by a wet towel or a lid.  As the water evaporates from the sand, it cools the inner pot and its contents. The whole thing is easy to build and to operate and, best of all, it is inexpensive.  An added bonus is that the water used for cooling does not need to be potable. That sounds perfect for third world applications and it is most often in this context that the device is discussed. 


True or False: Charcoal is a principle component of gun powder?

True.  Gunpowder also known as black powder is a mixture of charcoal, sulfur and potassium nitrate (saltpeter).  The charcoal and sulfur act as fuels and the saltpeter acts as an oxidizer. Sugar could also be used as the fuel instead of charcoal. A traditional ratio of the ingredients would be about 15:3:2 potassium nitrate, charcoal, and sulfur by weight.

A word on how it's made:

What secret don’t survival books teach you about making fire with friction?

Example of fire by friction image by Steve Sanford for Field and Stream. 
Hand Fire Drill

Answer: The type of wood used for the spindle and hearth board is crucial to making an ember. This is an often overlooked fact in many descriptions of making fire by friction.

What you are trying to do is create a very fine wood dust and then heat it to between 371-426°C (700-800°F). When that occurs, the wood dust starts to glow and it forms an ember much like the tip of a lit cigarette. That glowing ember can then be coaxed into a flame by adding it to a bundle of very dry tinder and blowing.


What secret would have allowed the ancient Egyptians to create hydraulic cement (like Portland cement)?

The Egyptians could have been building structures out of concrete if they had only known the secret to making hydraulic cement.  In the early 19th century, a bricklayer named Joseph Aspdin in Leeds, England first made Portland cement by burning powdered limestone and clay in his kitchen stove. He named it Portland cement because of its similarity to Portland stone, a type of building stone that was quarried on the Isle of Portland in Dorset, England.

What two secrets do you need to know about knapping in order to create stone tools?

Knapping can be an incredibly complex art that can require years of experience to create beautiful and functional tools. But knapping, in its simplest form, is banging two stones together causing one to fracture and create a sharp edge. That edge could be used as a crude tool as it is. Probably 80% of the tasks you would need to tackle could be done with that edge. The next 15% of refinement would probably take weeks or a few months to learn and the last 5% of refinement may take years.


You want to make a stone tool. What type of stone should you look for?

Chert formations, Pindus mountains Greece(source: candiru)
Examples of Chert

Our ancestors discovered that certain stones were very hard and, when broken, they formed very sharp edges.   These were logically used to produce cutting tools such as knife blades, arrowheads, axe heads and scrapers.  Geologists have refined classification of these various stones into categories such as flints, cherts, jaspers, chalcedonies, agates, quartz, obsidian, etc.  For the purposes of simplicity it is easy to lump them into two broad categories: Flint-like and obsidian. 

How hot can you get a coal fired forge?

According to "Marks' Standard Handbook for Mechanical Engineers", 10th, coal gas burns at about 3,590°F (1,977°C) under 100% air conditions. More or less air will decrease the temperature. This means that the maximum temperature of a coal fire in a forge is about 3,500°F (1,927°C).


How hot does a typical campfire get? Is it hot enough to melt silver?

This government publication on the thermal performance of masonry chimneys and fireplaces didn’t find temperatures greater than 855°C and that was the gas temperature in the flu.  This test of a rocket stove found a maximum average temperature of 945°C and a max temperature of 1049 °C. The third paper found that for small flames (less than about 1 m base diameter), continuous flame region temperatures of around 900°C should be expected. For large pools, the latter value can rise to 1100~1200°C.


True or False: Concrete can be made by mixing powdered limestone, sand, gravel and water?

Interesting use of concrete for construction  (source: seier+seier)
The Pilgrimage Church by Gottfried Bohm was opened in 1962 in Neviges Germany

Concrete is the most often used construction material of the modern world.  It is simple and economic to make and if the Egyptians had known the secret they could have made it 4000 years ago. To make concrete, first you need to make the cement (or mortar) that holds the concrete together. 

The Romans did this by burning limestone (which is mostly calcium carbonate CaCO3) to create something called quick lime (calcium oxide CaO). Burning isn't quite the right term because "to burn" usually indicates an oxidation process which involves the "chemical union of oxygen with any substance".  What actually happens in a lime kiln is that the temperature of the limestone is increased to a point above its dissociation temperature.  The earliest lime kilns were really just layers of wood and limestone stacked together and lit like a giant bonfire.  So it is easy to see why it is called burning limestone when it really isn't.

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