How to Create an Outline from a Photo Reference

We are not all gifted with the ability to draw what we see even though we are good watercolour artists, however this should not stop us from being able to get a reasonable sketch from a photo reference onto our watercolour paper ready to begin the painting process.

One of the simplest ways of transferring a photo image to our paper is to use the Frisk Tracedown product. This is like carbon paper but it is coated with graphic powder on the back so that any pressure on the front transfers the graphite powder to the watercolour paper. Sometimes though using a photograph makes it hard to see which are the important lines to transfer to the your painting paper and I have discovered a method that I would like to share with that makes the process even easier to do.


I have discovered a fairly simple sequence of actions to follow using the free GIMP graphics application that runs on MS Windows to create a clear outline from a detailed photo image. Once you have this clear outline from your photograph you can then decide which elements you need to trace so that the important features get transferred in the correct proportions and perspective – two areas that cause most of us the biggest problems when we are sketching out our initial drawing.

This is the reference image I used for this demonstration which is a photo I took of the Bombay Distillery near Basingstoke:

This is the sequence of steps to follow:

  1. Having loaded in your photo reference image Select Menu Filters – Edge Detect – Edge and that will produce this effect:
  2. Now you need to invert this image so select Colours from the menu and then Invert and you will get this effect:
  3. Finally I have found it best to convert this image to a more black and white version for clarity by choosing Colourize from the Colour menu option and then in the popup dialog move the slider across to the left and position it half way down so that you end up with this:
  4. This is now a good clear outline to work with and makes it easy to pick out the important lines to transfer to your watercolour paper.

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Alternative to Gator Board

Gator Board Alternative

I have been investigating the availability of Gator Board, which is readily available in the US but not here in the UK. This board is very handy for stretching watercolour paper using the stapling method. The only outlet I can find that supply Gator Board is Jackson’s Art Supplies!

I decided to see if I could find an alternative board that was readily available, inexpensive to purchase and that would allow wet paper to be stapled to it for stretching without the board warping during the drying process.

Firstly I tried a couple of the so called “Foam Boards” but as they are not coated top and bottom with a wood veneer they weren’t successful at all and they were very expensive options.

Next I turned my attention to a board that is made from used newspaper and cellulose called “Sundeala Pinboard”. This is primarily produced to be used as pin boards on the wall which is what attracted me to it. In the US they call this board “Homasote Baord” however it is a slightly different construction to Sundeala Board. Although this board worked well, is readily available and held the staples during the paper drying time, unfortunately it isn’t rigid enough to stop the paper warping the board! It is also a very expensive option to use, a small piece measuring 60cm x 30cm costs around £20.00.

However I have now experimented with Oriented Strand Board (OSB). It is a type of engineered wood similar to particle board, formed by adding adhesives and then compressing layers of wood strands in specific orientations. This board is quite dense and I was able to find an off-cut at my local hardware store that I purchased for £2.00 to try it out! I think that this board is probably the answer as it ticks all of the boxes as far as requirements go and most importantly it is much cheaper to buy. B&Q sell it in 810mm x 410mm x 9mm for just over £7.00 and this is large enough to make two 1/4 imperial sized stretching boards.

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