Celtic knotwork and computers

Celtic knotwork has been an interest of mine since I first learned how to draw a simple knot nearly half a century ago.
I came across a booklet while babysitting and was hooked.  I can't remember anything else about the booklet but the method (which clearly owes a lot to the work of George Bain) is just four simple steps ...

How to do it by hand

... OK, if you can't wait, have a look here and here to find out how a computer can help, but come back again to see how it used to be done!

Step one:

draw a line - preferably in a repeating pattern. Almost anything will do to start with but it won't work if you have more than two lines crossing at a point. Join up the end and the beginning and try not to let the spaces get too small. 		draw a line
thicken it

Step two:

thicken the line by drawing all the way round the outside and inside the spaces - the smallest space decides how fat the line can be. Try to keep the same distance from the base line all the way.

Step three:

interlace carefully, following your base line and going alternately over and under. This will always work out correctly if you've followed the rules. 		interlace
tidy up

Step four:

take away the original line and you should be left with a nice clean interlaced knot!

Finally, the fun part - decorate any way you like

 simply colour photoshop effects bevel and stone


How to do it better

So, it's very easy to get started, but you soon realise there's a lot more to creating a good looking design than just doodling aimlessly. Study the sources and you'll probably notice the most pleasing designs have repeating patterns and an underlying symmetry.

That's where graph paper and grids of dots can help.

doodle

When I was about five my mother taught me to draw this design and I've doodled it ever since.
That's probably why I like this method of creating a 'starting line' for my knots:

Begin with a grid like this with the dots in the second row under the gaps in the first. If the distance between alternate rows is the same as the gap between the dots you get a 'Celtic' knot. For 'Pictish' proportions the ratio should be 4:3

 dots
walls

Now add a few walls to act as turning points by joining dots horizontally or vertically. Keep the pattern symmetrical and don't overdo it.

Draw the starting line along the diagonals between dots. When the line hits a 'wall' bounce off it along the next diagonal and do the same when you run out of dots at the edge.

 line
knot

Check that the finished knot is a single line - this isn't essential, but it's best not to have any obvious closed loops. Thicken and interlace and tidy up to finish drawing your knot

Now you can ink in the line and colour your new creation in any way you like.
Or scan your design into a computer and use whatever special effects your paint package has.
Experiment and see what works ...

 special effects

Make it bigger

Once you've got a simple single-line motif you can join a few of them to make a border by drawing them side by side and replacing a turning point by a crossover:

or to make a larger block join four motifs corner to corner:

four joined motifs

then you've got a bigger motif that you could turn into a border or an even bigger block ... or join different motifs or ...

The next step

You don't have to stick to rectangles though. Once you've got the hang of creating a base line you can bend and stretch the outline and combine different knots in any way you like.

Or you can ditch the rectangles altogether and build your motifs and your knots on triangles or hexagons, or any shape you can imagine.

 three triangle knots joined with crossings