How To Draw Celtic Key Patterns
Key patterns are just another variation on that most loved of Celtic designs – the spiral. Of course, they are made of straight lines and triangles, and look nothing like traditional Celtic spirals, but that is what they are.
The S-curve was one of the more common Celtic spiral elements. If you take a lot of S-curves, you can link and repeat them.
The basic key pattern is drawn the same way, but with straight lines. Start at a central point, and draw a straight line 1 unit long. Then rotate by 90° and draw a straight line 2 units long, rotate by 90°, draw a straight line 3 units long, and so on.
To make it into a key pattern (or to make the spiral an S-curve), simply copy the spiral, rotate it by 180° and stick the 2 ends together.
Unfortunately, this is not quite right, because what has just been made is a typical classical fret pattern, and the difference is this: with the fret, if you repeat them as we did with the S-curve, you get a basic diagonal single line border:
Which, while it may look nice, is not quite Celtic. It does repeat to form an interlinked block, but the edges do not lend themselves to embellishment the way that key patterns do.
Almost exclusively, key patterns were used to decorate borders or blocks; so they needed to repeat horizontally or vertically. It was a simple move, therefore, to rotate the whole design through 45° to fix this. So developed the distinctive Celtic variation of one of the most widespread forms of decoration;
Key patterns differ from classical fret not only by this change of angle. This small change leads to a wealth of embellishment, creating a much greater library of designs than any other culture managed before or since with fret patterns. As in the science of fractals, a small change can make a huge difference.
There is a tradition in art history from the nineteenth century, which some still hold to be true, that all real art in Europe developed from Roman and Greek art, and that before the Romans came to Britain there was no indigenous art form. Therefore Celtic key patterns must have developed from classical fret patterns, brought to the area by traders, although of course this ignores the archaeological evidence of widespread trading in prehistoric times. This may be the case. The same argument could be used to claim that key patterns came from the Chinese, as there is archaeological evidence of indirect trade with China. It could also be argued that the Celts developed their art forms from a slightly different branch of the same basic geometry. After ail the British Museum has an Egyptian carving showing a key pattern panel from around 3000 вс and there are mammoth tusks from the Ukraine carved with key patterns from 15,000 вс.
Surely it is not the ancestry of such patterns that is important, but the fact that the necessary change was made, enabling a completely different-looking series of patterns to be drawn. As far as I know it was the Picts, Celts from the north of Scotland, who developed these particular patterns, explored their possibilities and left us a rich collection, showing us the possibilities of the key pattern. And to take it one small step further, it is not where, when and by whom they were discovered; the important thing is what you can do with them. And the better you understand them, the more that you can do with them, so on with the numbers.
As we have seen, key patterns are just simple S-curve spirals made with straight lines. The numbers to describe them are just as simple.
We’ll start with one of the most basic key patterns to make things even simpler. The first line is 1 unit long. The second must be 2 units long so that there is a gap of 1 unit on either side of the interlocking key.
The third line must be 2 units longer than the first for the same reason.
The fourth must be 2 units longer than the second for the same reason, and so on.
In this case the fourth line is the ‘backbone’ of the key, joining the 2 symmetrical spirals on either end. By looking at the pattern you can see that the length of the line is the length of the second line of the key, plus the length of the third line in the next key, plus the ubiquitous 2 to separate the keys.
To simplify this we can write it as a basic formula, where x is the length of the first line and V is the length of the second line:
x, y, x+2, y+2, x+4, y+4, x+6, y+6, and so on, until the ‘backbone’, which is (x+a)+(j+b)+2 i.e. two units longer than the two previous lengths added together.
And it gets simpler. The second line must always be 2 units long in order to separate it from the last line of the interlocking key.
So in the above equation у = 2, so it can be rewritten x, 2, x+2, 4, x+4, 6, x+6, 8 and so on.
The first 7 key patterns that this gives for x = 1 and x = 2 are
From this you should be able to see the pattern and create your own absurdly convoluted key patterns, if you so wish.
There is now just a single piece of information stopping you from using these keys. Remember that key patterns are repeat patterns; in other words, the same pattern is repeated to fill a larger area. What we need to know is how many units high and wide the pattern is. Of course the key itself is the repeating pattern, but for our purposes (actually fitting the keys into an area), it will be far simpler to find a square or rectangular section that will repeat itself horizontally and vertically.