The Double Dangerous Book for Boys. Conn Iggulden

can still be valuable, even wondrous. Perhaps there is a lesson in kintsugi about scars and how we see ourselves. It is not difficult to imagine a bowl or vase with special value – the gift of a loved one, for example. Allowed to drop, it would break into pieces and seem impossible to fix. Yet perhaps, a dozen quiet evenings later, something beautiful might emerge.

      There are pieces of ceramic that are masterworks in themselves, of course. For such a fragile material, it’s amazing they survive for the centuries they do. You might see iron bands worked into one of those to hold an old break together. This is not that practical solution – kintsugi is an art form in itself.

      Now, obviously we can’t manage the expense of gold dust, silver or platinum. Ours was strictly a cheaper project. Our white vase came from Hobbycraft, as did the glitter and glue. Make sure you get a glue that can handle a ceramic break. The Japanese use resin or lacquer.

      For the purposes of testing it for this chapter, we thumped the vase once with a club hammer and broke off a piece. If you have shattered a vase into forty different pieces, don’t despair. It will take a long time to complete a job that has to wait for glue to dry at each stage, so bear that in mind.

      If we simply reglued the broken piece, even with glitter mixed into the glue, it would form a hairline and be almost invisible. The idea is for the break lines to be as obvious as possible. Take a steel file and remove the edges of the broken piece and the rest of the jug. Try not to break it or send anything flying across the room. The idea is to widen those cracks. You might try refitting the piece every now and then to check your progress.

      When you’re ready, mix up a batch of glue and glitter. PVA glues will dry clear, leaving the glitter visible. However, our best result came from a premixed glitter paste. Slather the stuff on liberally and replace the broken piece. Of course, as you’ve filed away the edges, you might find it doesn’t stay in place any longer. Having a roll of masking tape around is extremely useful.

      Wipe as much of the glitter-glue away as you can while it’s still wet – it’s trickier to remove when it’s dry, especially if the piece of pottery isn’t glazed. Try not to get too much of the glitter on you as well. This is a fairly messy process, but the results can be rather lovely. The most valuable thing you will ever own is your time. Using some of it to make a thing of beauty cannot be a bad thing – and reminding yourself that broken things can be fixed is always worthwhile.

       THE FASTEST LACES IN THE WEST

      We all learn a simple way to tie shoelaces when we are kids. This technique – sometimes called a butterfly knot – is at least twice as fast. You appear to tie the knot in one quick movement, which impresses onlookers. It might look tricky, but it’s one you can learn very quickly. Once you have done it a few times, you’ll never go back to the old loop-loop-knot method again.

      Note: This is much easier to do than to describe! Follow these instructions while you try to tie the knot on an actual shoe. Just as when you first learned to tie a shoe – it gets much easier.

      1. Begin with the traditional cross-over. Regardless of how you tie your shoes, you might want to put one lace through a second time. It forms a triple, which has more friction and so locks every knot in place. Your shoes will come untied less often if you take nothing but this away.

      2. Note and practise the finger positions in the next pictures until they are second nature. Thumb and middle on the right hand, index and middle on the left. The idea is to form and bring both loops together in the same movement, completing the knot in one swift tug.

      3. Rotate each hand – the left clockwise to bring the thumb underneath, then anticlockwise to form an upside-down U or open loop.

      4. The right hand moves anticlockwise to bring the second/index finger up underneath, then clockwise to form an upside-down U or open loop.

      This probably seems impossibly complex at this point. Just remember – there is nothing wrong with complexity. If something is hard, we don’t give up. We grab it by the throat and throttle it until it’s easier. In this case, that might mean sitting with a shoe on a table and the book propped open next to you for ten minutes, but the principle is clear enough.

      5. It helps to form exaggerated open loops when you are learning. Bring them together, right hand over the left hand, holding the four points taut – the two bends and two grips.

      6. When the right-hand lace is brought over to the left hand, it forms a capital letter A.

      7. With the thumb and forefinger of the right hand, grasp the crossbar of the A.

      8. With the thumb and forefinger of the left hand, grasp the lower left leg of the A.

      9. Pull gently – and the familiar twin loops will form.

       FINDING THE HEIGHT OF A TREE

      If you want pinpoint accuracy, there are laser devices on the market that will give you precision in a split second. This is more for those who want to know if a tree will hit their roof when it blows down. Or just because the basics of trigonometry are interesting.

      YOU WILL NEED

       A protractor

       A pencil

       A bit of Blu Tack

       A calculator

      Trigonometry has to do with triangles. It’s the branch of mathematics that examines the relationships between the lengths of the sides and the angles. You probably already know that the internal angles of a triangle always add up to 180°. That is one of the first things you learn – so if we know one angle of a triangle is 40° and another is 80°, the last has to be 60°, because 40 + 80 + 60 = 180.

      So whether it’s an equilateral triangle, where all the sides and angles are equal:

      Or an isosceles triangle, where at least two sides are equal:

      … the internal angles always add up to 180°. You might also be interested to know that angles along a straight line also add up to 180°. If you think about it, 180° is half a circle of 360°.

      If you drew a straight line and crossed another through it, you would have two right angles of 90° – for a total of 180°. Four right angles, or 4 × 90 = 360 – the full turn.

      That means, just as a matter of interest, that if you know any internal angle of a triangle, you can extend a straight line and also know the external angle. That might