The Byzantine emperor, a Christian monarch who lived in Constantinople, needed help.
He turned to the pope, who in 1095 called for all Christians to start a holy war against the
Suljuk Turks. Thousands rushed to join the Crusader armies. They crossed into Palentine
and recaptured the important cities of Nicaea and Antioch. Jerusalem fell in 1099 after a
desperate siege lasting six weeks, and the Crusaders took terrible revenge by slaughtering
thousands of Muslims. There were to be three more crusades: one in 1144, the second
in 1187 and finally the Children’s Crusade in 1212. Fifty thousand children set off from
France and Germany for the Holy Land. Many died on the journey, many more were
captured and sold as slaves in Africa.

Traditionally, glue is made from boiling up the bones, skins and other parts of animals such as fish
or horses in order to extract the gelatin, which is then purified and concentrated to make a sticky
substance that will form a bond as it dries. There are now many different types of glues, made from
plant material or minerals such as petrol, as well as different kinds of synthetic glues. One of the
simplest glues is flour-and-water paste and traditional wallpaper paste is made with starch. Latex
adhesives were originally made from the latex extracted from rubber trees, but synthetic forms are
now also available. Another type of synthetic glue is epoxy resin, in which the user mixes an adhesive
substance with equal quantities of a hardener. The two substances react chemically together, causing
the adhesive to set rapidly. Glues are widely used in many industries, such as furniture-making and food-
packaging.

There are a few factors that govern how valuable a stamp is to stamp collectors: the most important
is how rare it is. Obviously, very old stamps are uncommon so these, such as the ‘Penney Black’ very
seldom come up for sale and so are unbelievably expensive. Other things that might make a stamp rare
might be where a mistake was made in the printing and the stamp was withdrawn after only a few had
been sold. Undamaged stamps are more valuable than similar ones that have been damaged.