Multiply is also really useful if you want to use a reference drawing. So for example say you found a map on google of a region you wanted to turn into a hand drawn map. Copy that image to your computer. Open up your parchment image as above. Open up the Google image and scale it so it will fit nicely over your parchment layer. Create a new layer over your parchment layer and paste the Google image on to it:

Click image for larger version. 

Name:	looe.jpg 
Views:	288 
Size:	224.4 KB 
ID:	4031

This gives you something like this. Now change the Layer mode to multiply and you get something like this:

Click image for larger version. 

Name:	looe2.jpg 
Views:	544 
Size:	375.6 KB 
ID:	4032

Now create a new transparent layer (remember shift-click), choose the ink tool and start tracing round the coastline, along roads and so on until you have a line drawing of the map you are after. This way you need never complain of lack of hand-drawing skills or inspiration again!

Now that we have got our ink lines by subterfuge, deceit or elbow grease, we'll move on to colouring the image tomorrow.