May 7, 2017

How to defend a city in 1880

There is a defense line of 42 forts that runs around Amsterdam that was constructed between 1880 and 1920. It is called the Stelling van Amsterdam (Dutch), and was commissioned soon after the Unification of Germany.

It was a defensive “water line”, which took advantage of the existing polders to flood tracts of land, preventing the enemy from advancing.

There were delays in construction — because of technical advancements in warfare, they had to be built from concrete instead of wood (a new building medium for the Dutch). The sand foundations also had to settle for several years before the concrete forts could be built on them.

It became obsolete as soon as it was finished due to the invention of the aeroplane and tank, and therefore was never used and was decommissioned in 1963.

1Stelling van Amsterdam, wikipedia

2Fort bij Aalsmeer © Documentatiecentrum Stelling van Amsterdam, Het Parool

April 24, 2017

How to identify an Egyptian goose

The Egyptian goose (Alopochen aegyptiacus) is a waterfowl native to Africa south of the Sahara and the Nile Valley. It is actually a cross between a goose and a duck. These birds were sacred to the Egyptians, who bred and domesticated them, and they appear often in Egyptian artwork.1 Small populations of escaped ornamental birds exist in Western Europe; the Netherlands has a population of around 100,000.2

To identify an Egyptian goose, look for chestnut patches around the eyes, an apricot colored breast, a mix of reddish and black tail feathers, a black-tipped pink bill, and pink legs and feet. It is about 25 to 29 inches long. When it is in flight, the white underside of its wings are visible.3

The Egyptian goose prefers to nest in large holes in trees near lakes, and are believed to mate for life.

1Egyptian Goose,

2Species Watch: Egyptian Goose, The Guardian

3Birding Information

April 22, 2017

How to illustrate infinity

“To illustrate an infinite number, one must have recourse to a gradual reflection in the size of the figures, until one reaches — at any rate theoretically — the limit of infinite smallness.” 1— Maurits Cornelis Escher (1898 – 1972)

fig. 1tessellation

The work of M.C. Escher explores themes of eternity, metamorphosis, and infinite movement which he achieved by playing with perspective, patterns, and tessellation. As an intuitive mathematician, he discovered these systems himself through experimentation.

fig. 2 honeybee cells

Escher achieves “infinity” in his work with repeating patterns — shapes along planes on a flat surface, also called plane tessellations. A plane tessellation is an infinite set of shapes fitting together to cover the whole plane once, with no overlaps and no gaps.2 Tesselations are found in nature, like in the hexagonal cells of honeycombs and in crystals.3 Nature is also a strong theme in Escher's work.

He saw tessellation as his most important theme, as “the richest source of inspiration” that he had ever tapped.

1To Infinity and Beyond: A Cultural History of the Infinite by Eli Maor

2Escher's Tessellations of the plane, Cornell

3Patterns in Nature,

April 17, 2017

How to turn leek into ash

Make two cuts in a leekprei, same as you normally would — one at the root, and one where the stalk turns from light green to dark. Save the white part for another time, discard the root.

Rinse any traces of grit from the dark green trimmings, and dry with a towel.

Place them on a baking tray in a single layer. Roast in the oven (with the fan off) until charred and black.

Let cool, grind into dust.

April 16, 2017

How to make mustard

“Grind seeds and add liquid.” 1

Mustard seeds contain a chemical that reacts with cold liquid — heat damages this reaction. Break the seeds first to release it: coarsely grind 6 tablespoons whole mustard seedsmosterdzaden (a mixture of yellow, brown, black).

Add ½ cup mustard powder, 2 teaspoons salt, and 1 teaspoon turmeric (for colour, optional). Stir in ½ cup of flat beer, cider, wine or fruit juice. mustard

Let sit for up to 10 minutes — more minutes = more mellow. Then add 3 tablespoons vinegar.

If using any herbs, spices or honey, add them. Wait at least 12 hours before using. Mustard will last in the refrigerator for at least 12 months, but due to its antibacterial properties, it will dry out before it goes bad.


April 15, 2017

How to cook broad beans

fig. a single bean

Separate the broad beans (also called fava beans or garden beanstuinbonen) from their pods. If they are older, larger beans, they need to be blanched to remove their waxy outer skins.

Boil a pot of water, submerge beans for 30 seconds, then remove to an ice water bath. Slip the skins off with your fingers.

Transfer to a fresh pot of water and simmer for 15-20 minutes, or just until tender.

Dress the beans with olive oil, salt and a fresh lemon juice.

April 14, 2017

How to grow peas

fig.peas in pod

Plant early in the spring, ideally a month before last frost, for peaserwten are best grown at temperatures below 21°C. A light blanket of snow will not bother pea plants.

Peas will appreciate a sprinkling of wood ashes to the soil before planting. Peas do not need to be fertilized. Plant seeds 1 inch deep and 2 inches apart.1

Peas (like other legumes) will fix nitrogen in the soil, making it a perfect home for nitrogen-loving plants like lettuce, tomatoes, and cucumbers.

Pick peas in the morning after the dew has dried, when they are the crispest. Keep your peas well-picked to encourage more pods to grow.

1The Old Farmer's Almanac

Today I Learned

A collection of the things I've learned each day — topics such as: food, history, design, code, gardening, languages, etc.


Romana Bold, Crimson Text, Inconsolata.

Clipart courtesy FCIT